News this Week

Science  07 Jan 2000:
Vol. 287, Issue 5450, pp. 22

    CDC Struggles to Recover From Debacle Over Earmark

    1. Martin Enserink

    Crossing Congress can be bad for an agency's health. That's the painful conclusion that the Centers for Disease Control and Prevention (CDC) has drawn as it tries to recover from a self-inflicted wound: the diversion of millions of dollars budgeted for chronic fatigue syndrome (CFS) into work on other diseases. In addition to angering patient advocacy groups and some legislators, the CDC has now been forced to tax other programs to replenish the CFS account. And even though the agency has apologized and sought extensive comment on a new CFS research agenda, officials face another round of investigations—as well as a complaint from an employee alleging that he was persecuted for revealing the misallocation.

    At the root of the controversy is $22.7 million that Congress earmarked for CFS research in 1995. In 1998, William Reeves, the agency's top CFS researcher and director of the Viral Exanthems and Herpesvirus Branch, filed a whistle-blower complaint charging that his superior, Brian Mahy, who heads the Division of Viral and Rickettsial Diseases, had used a large part of the special funds for other purposes. He also alleged that CDC officials tried to cover up the reallocation during oversight hearings before Congress. His claims were backed up by the inspector general of the Department of Health and Human Services, who in May 1999 found that only $9.8 million had definitely been spent on chronic fatigue research. Some $8.8 million had gone to poxvirus, human papillomavirus, measles, polio, and other research within Mahy's division, she reported, and it was impossible to tell how the remaining $4.1 million was spent. The report also said that CDC's acting director, Claire Broome, had provided lawmakers with “inaccurate and potentially misleading” data about the program.

    In July, CDC's new director, Jeffrey Koplan, acknowledged the diversion, apologized to Congress and CFS patient groups for a “breach of CDC's solemn trust,” and vowed to restore the disputed $12.9 million for CFS research over the next 4 years. To prevent future episodes, CDC has mandated financial training for all its managers, and Mahy's divisional budget will be handled by Koplan's office until 2001. CDC says the corrective measures are “the most far-reaching in the half-century history” of the agency. Mahy has declined to comment on any aspect of the controversy.

    CFS, also known as myalgic encephalopathy, is a mysterious, debilitating disorder that robs patients—mostly adult Caucasian women, according to an as-yet-unpublished CDC study—of the energy needed for even the most basic tasks. Although it has been called chronic fatigue syndrome since the late 1980s, records of related afflictions go back more than a century. However, researchers have so far failed to link the disease to an infectious agent or another organic cause.

    Patient groups such as the Chronic Fatigue and Immune Disorder Syndrome Association of America (CFIDS) say that the lack of clear etiology has led many researchers to see CFS as a psychosomatic disease, which has reduced scientific interest. “There is an element of bias at CDC,” says CFIDS executive director Kimberly Kenney. “They feel that if there was something to be found, they would have found it by now, and therefore it doesn't warrant much more intensive research.”

    Agency officials disagree, saying that the reallocation of funds was mostly the result of poor accounting practices. “We have many brilliant scientists who are, frankly, not very good managers,” says CDC spokesperson Barbara Reynolds. In addition, Joseph McDade, deputy director of the National Center for Infectious Diseases (NCID), says that public health emergencies such as last summer's West Nile virus epidemic in New York City can require CDC to reshuffle resources suddenly. “When you have large outbreak investigations, it's sometimes difficult to fund those and continue other programs as well.” Indeed, some researchers both within and outside CDC say that there may well have been sound scientific reasons to emphasize diseases known to be infectious rather than something as elusive as CFS. “Of course you shouldn't break the rules,” says Jack Woodall, a former CDC researcher who now directs the Center for the Study of Emerging Infectious Diseases at the Federal University of Rio de Janeiro in Brazil. “But I'm sure [Mahy] did what he thought was in the best interest of public health.”

    In the wake of the government inquiry, CDC has drawn up a “reinvigoration plan” to understand the disease. The new strategy, to be finalized in February after a series of hearings, includes a nationwide study of the prevalence of CFS and efforts to increase awareness of the disease. It will also pursue a new approach to finding a cause, comparing gene expression patterns between patients and healthy people and using advanced techniques to detect new pathogens. “Now that we have complete and unfettered control over the money, the program is going very well,” says Reeves, who manages the effort.

    But although the CFS program may be back on track, other research programs may be knocked off balance. Most of the money will come from the $217-million-a-year budget of NCID, which includes Mahy's division. Reeves says CDC as a whole should absorb the loss. “This is going to severely compromise NCID's ability to do important infectious diseases research,” he warns. But McDade predicts that things will work out. “Every year there are many things that need to be done, and there are always challenges about resource allocation,” he says. “This is just one more challenge.”

    Finances aren't the only obstacle to full recovery for CDC. Reeves, who is protected by a federal whistle-blower law, has filed a complaint with the U.S. Office of Special Counsel in Washington, D.C. It claims that Mahy, upset at his speaking out, issued him an unjustified reprimand, reduced his performance appraisals, and removed staff from his supervision. Reeves says he wants those actions undone and is also asking for recovery of attorney fees and $300,000 in damages. McDade says CDC hasn't been officially notified of the case and declined to comment.

    Meanwhile, the General Accounting Office (GAO), Congress's financial watchdog, is taking a closer look at chronic fatigue research at CDC and its sister agency, the National Institutes of Health. That study, to be completed in the spring, “will be a qualitative assessment of the [scientific] program,” says GAO researcher Janet Heinrich. The study was requested by Senator Harry Reid (D-NV), a champion of CFS patient groups who helped obtain the special funding.

    Whatever these investigations and studies conclude, CDC isn't likely to make the same mistake twice. “We have learned a valuable lesson through this experience, which will not be forgotten,” said a statement that Koplan sent to patient groups this summer. For Woodall, that lesson is elementary: “As we all know, you have to be careful with what you do and how you deal with the people who control the money.”


    Kinesin Movements Revealed

    1. Elizabeth Pennisi

    Edwin Taylor and Nobutaka Hirokawa are not your average mechanics. Instead of tinkering with grease and iron, they study the cell's molecular motors. And unlike ordinary mechanics, who know that all engines are basically alike, Taylor and Hirokawa are finding an unexpected diversity in molecular motor design. Take kinesins, motor proteins that drag protein-laden vesicles along microscopic tracks called microtubules to the cell's periphery. Last month, at the annual meeting of the American Society for Cell Biology, which was held in Washington, D.C., Taylor, a cell biologist at the University of Chicago, and Hirokawa, a cell biologist at the University of Tokyo, described new results showing that two different kinesins move in very different ways.

    The classic “double-headed” kinesin studied by Taylor and his colleagues plods systematically step by step along the microtubules, whereas the single-headed variant kinesin studied by Hirokawa ambles forward, relying on random movements to make progress. What's more, both kinesins move differently from myosin, a motor protein involved in muscle contraction. Some cell biologists had expected that the two-headed kinesin in particular would work in a similar fashion, partly because it and myosin both consist of two subunits, each with its own business end, or “head.”

    Cell biologists had learned that myosin moves when one head swings out like a lever and pulls the protein along the actin filaments of the contractile machinery. But Taylor found something quite different when he became part of a team led by Ron Vale, a biophysicist at the University of California, San Francisco, and Ron Milligan, an electron microscopist at The Scripps Research Institute in La Jolla, California. By attaching fluorescent probes or gold beads to each kinesin subunit, the researchers were able to use a variety of techniques, including electron microscopy, to monitor the molecule's shape and movements. In some experiments, for example, they treated the protein with altered versions of ATP, the energy-rich molecule that is the “fuel” for motor proteins, which caused it to freeze at various stages in the movement cycle.

    The researchers found that the kinesin moves one foot at a time. First, ATP binds to the front foot, causing a 15-amino-acid region called the neck linker to zip up with a nearby part of the molecule and stiffen. This stiffening yanks the back foot off the microtubule, swinging it ahead of what was the front foot. Then, ATP can bind to the new front foot, and as this process is repeated, the kinesin motor plods along, with cargo in tow. “The motion here is a much smaller change” than the one seen with myosin, Taylor said in his talk at the cell biology meeting. (The work also appeared in the 16 December 1999 issue of Nature.) Or as Thomas Pollard, a cell biologist at The Salk Institute in La Jolla, puts it, “The myosins are dancing while kinesin is hiking, steadily chugging along step by step.”

    Hirokawa found that the kinesin called KIF1A works quite differently, however. In early 1999, the group reported a preliminary clue: They found that KIF1A moves on its own, without pairing off (Science, 19 February 1999, p. 1152). Now the researchers have an idea of how it does that.

    The starting point for the new work was their finding that although the KIF1A gene is quite similar to other kinesin genes, it has extra bases that code for a sequence of six lysine amino acids. Thinking that the lysines might be the key to this kinesin's ability to move solo, the researchers synthesized the part of the protein containing the sequence and used cryo-electron microscopy, in which samples are stabilized in glassy ice, to examine how it interacts with microtubules. They also made other versions of this part of KIF1A, varying the number of lysines to see whether that affects KIF1A's movement.

    The electron microscopy studies revealed that KIF1A grasps the microtubule both with its foot and the stretch of lysines, which form part of a positively charged loop that is attracted to the negatively charged tubulin protein in microtubules. Based on that finding, Hirokawa proposed that the loop acts as a sliding clamp that holds KIF1A to the microtubule as it moves.

    The studies of KIF1A with altered numbers of lysines bore this idea out. “If we take the lysines out, [the motor] doesn't work,” Hirokawa's Tokyo colleague Masahide Kikkawa said when he presented some of the KIF1A data at the meeting. “It's very nice work and leads to new questions,” such as what biases KIF1A's movement in one direction, comments David Hackney, a biophysicist at Carnegie Mellon University in Pittsburgh.

    Taylor thinks there may be still more kinds of motors chugging away under the hood of the cell. “The mechanisms you can generate from the [general myosin-kinesin] structure are much broader than we had thought,” he explains. “There are a whole bunch [of these proteins] out there whose details have not been worked out.”


    Satellite Radar Spies City Subsidence

    1. Alexander Hellemans*
    1. Alexander Hellemans writes from Naples, Italy.

    Naples, Italy—For the past 9 years, researchers have been using the European Space Agency's remote-sensing satellites ERS-1 and ERS-2 to detect small movements of Earth's surface caused by earthquakes or volcanic activity, thanks to a technique known as radar interferometry. One team of researchers based here has been studying movements in Campi Flegrei, a volcanic area west of Naples, since 1992, when ERS data for that area became available. Much to their surprise, in recent images the researchers noticed that a well-defined 4-square-kilometer area of Vomero, a part of Naples, appeared to have subsided. “We observed that between 1992 and 1996 there was a rather significant subsidence of 5 to 6 centimeters,” says Riccardo Lanari of IRECE, Italy's National Research Council laboratory for research in electromagnetism and electronic components in Naples, noting that this is the first time subsidence has been detected this way in a city.

    At first, the team thought this apparent slump was a data error or due to atmospheric effects, until they noticed that it coincided, in both location and time, with the construction of a new underground railway line. The researchers have informed the city administration of Naples, as well as civil protection authorities and the railway company, about their discovery.

    The two ERS satellites produce detailed radar images of the ground by bouncing pulses of radar waves off the surface. Radar interferometry involves taking an image of a certain area of terrain and then snapping the same spot some time later. Using a computer, one image is subtracted from the other. If there has been no change in the terrain, the resulting interferogram will be blank, but if the terrain has shifted, some of the reflected waves in the second image will be out of step with the corresponding waves in the first. This “phase” change will show up on the interferogram as interference fringes, each of which corresponds to a displacement of the surface of half the wavelength of the radar waves, which in the case of the ERS satellites would be 2.8 centimeters.

    Using this method, the Naples team has detected ground movements in Campi Flegrei of as much as 25 centimeters. At first the team dismissed the much smaller shifts in Vomero as artifacts. However, they kept finding the same fringes consistently in several interferograms generated from data taken over different time spans. Lanari recalls that one of his co-workers said: “Hey, this is the area where they are building the metro.”

    From a study of 45 interferograms spanning different time periods, the subsidence became apparent in 1992 and coincided with the excavation of the new metro tunnel under Vomero. When the team superimposed the trajectory of the underground line on the interferograms, they found “a very strong correlation between the location of the maximum subsidence and the development of the underground. … It is clear, and there is no discussion,” says Lanari. They also observed that the subsidence gradually slowed after 1996 when excavations were completed.

    Team leader Giorgio Franceschetti of the University of Naples says that their fortuitous finding may open up a variety of applications for radar interferometry. It could be used to keep an eye on densely populated areas where human activity may be affecting the stability of surface terrain, such as the Padano area near Venice, where natural gas is being extracted, and an area of Paris where other researchers believe they have already detected subsidence of about 1.5 centimeters. Jean-Claude Souyris of France's space agency, the CNES, in Toulouse confirms that “preliminary results” obtained using the same satellites show subsidence in a 100-meter-square area around the Condorcet metro station in Paris.


    Zoology Naming Rules Eased

    1. Elizabeth Pennisi

    While most of biology has kicked into hyperdrive, taxonomists pride themselves on keeping their research in line with work done decades, even centuries, ago. That means sticking with the principles that each organism's true name be the oldest one appearing in the print literature, all names be in grammatically correct Latin, and any deviations from these rules be approved by an international commission. But even taxonomists are feeling the pressure of our accelerated pace of life, as shown by the new edition of the International Code of Zoological Nomenclature, (ICZN) a set of naming rules that first came out in 1905 and was last updated in 1985.

    The code, newly revised under the auspices of the International Commission on Zoological Nomenclature, allows its users to make some time-saving changes and even begins to bring zoological nomenclature into the digital age. Still, a few researchers fear that the revisions don't go far enough in preparing the field for the 21st century. “A lot of people wanted a lot more changes,” notes William Eschmeyer, an ichthyologist at the California Academy of Sciences in San Francisco.

    To its credit, the new, fourth edition “gives individual scientists a lot more authority” to sidestep priority when they find an early name if that name has not been in use for at least 100 years, says Eschmeyer. It also relaxes some rules for making sure that the Latin spellings of names are correct. And while the old rules required that descriptions of new animals or name changes be printed in a journal, the new code allows researchers to publish them on compact discs, as long as “identical and durable copies” are put in at least five libraries that are accessible to the public. The World Wide Web, however, is not acceptable, nor are electronic journals, says Alessandro Minelli, a zoologist at the University of Padova in Italy.

    To streamline searches for existing species names, the code opens the door to the establishment of official species lists that anyone could check. “There are many lists in progress,” notes Minelli, president of the commission, but there is no agreement yet on exactly how the lists should be set up or kept current. That, he says, may be in the next revision.

    At least one of the revised code's new authors, entomologist F. Christian Thompson of the U.S. Department of Agriculture systematics laboratory at the National Museum of Natural History, wishes that the commission had not put off that step, however, and that the code had also gone further in eliminating Latin requirements so as to make it easier to automate and computerize taxonomic data. Indeed, Thompson worries that there might not even be a “next revision.” Over his 25-year career, he says he has seen a steady decline in the number of taxonomists as the pace of progress in other areas of biology lures budding scientists. “With fewer and fewer people [in the field], I'm not sure we could assemble a core group of people to do this again,” he says.


    Academy Plans Guide to Improve Status

    1. Jeffrey Mervis

    “I'm taking a risk just being here. Missing a day of work could raise questions about my priorities.” That frank statement from Daniel Zuckerman, a physiology postdoc at Johns Hopkins Medical Institutions in Baltimore and president of the university's Postdoctoral Association, reflects the vulnerability that many postdocs feel today. But Zuckerman was among friends: His comments were made at a workshop held late last month by the National Academy of Sciences (NAS) that was aimed at reducing that vulnerability for the 40,000 postdocs who contribute mightily to the U.S. research enterprise but rarely receive commensurate pay, rights, or recognition.

    Zuckerman and 100 other people crammed into an academy conference room in Washington, D.C., to offer advice to its Committee on Science, Engineering, and Public Policy (COSEPUP) on a publication due out in the fall. Its “Guide to the Postdoctoral Experience” will describe issues facing these fledgling scientists and advise all the players—graduate students, postdocs, mentors and supervisors, university administrators, and the government agencies whose funding keeps the system afloat—of their rights and responsibilities. (Questions and comments may be sent to cosepup{at}

    The status of postdocs is a hot topic in academic circles (Science, 3 September 1999, p. 1513). Last month, for example, the Association of American Medical Colleges adopted a 1998 report from the Association of American Universities that tells institutions to define the position clearly; set “realistic” salaries and benefits; standardize hiring, training, and evaluation practices; and create an office to enforce these policies. A growing number of universities have already taken such steps, and a dozen postdoctoral associations have sprung up to negotiate better working conditions and raise postdocs' visibility.

    The academy hopes its guide will move this process along. Discussion of a draft ranged from tips on setting up a central postdoc office to questions of whether performance appraisals are an important management tool or a waste of time. But it was pay and working conditions, especially in the life sciences, that brought emotions to a boil. “The issue is one of basic fairness,” said immunologist Jack Bennink of the National Institute of Allergy and Infectious Diseases, speaking about the 2800 postdocs on the National Institutes of Health (NIH) campus. “If we don't pay them a living wage, in 10 years [U.S. science] will be hurting for talent.”

    Many participants professed surprise that institutions follow the scale for NIH's National Research Service Award fellows, which starts at $26,252. “We couldn't get approval for anything under $35,000,” said Massachusetts Institute of Technology electrical engineer Mildred Dresselhaus, a COSEPUP member who chaired the workshop. And even that amount may be low: NASA's Jet Propulsion Laboratory and the National Institute of Standards and Technology pay in the mid- to upper $40s, representatives noted, while Eli Lilly's Jean Labus said the Indiana drug company starts its life science postdocs at $42,000. And although university officials defended the practice, they admitted that the system is flawed. “Physicians are also required to work a period of low-paying servitude, for which they are compensated the rest of their lives with higher pay and guaranteed employment,” noted H. F. Gilbert of Baylor College of Medicine in Houston. “Unfortunately, we can't do that for postdocs.”

    Dresselhaus says the guide won't recommend a specific pay floor—“it would be hard to get anything through [NAS] review that was opposed by NIH or the biomedical community,” she confesses—or prescribe certain practices. “But we hope people will use it as a basis for further discussion.”


    Army Corps Seized by Dam Indecision

    1. Charles C. Mann,
    2. Mark L. Plummer*
    1. Mann and Plummer are the authors of Noah's Choice.

    Portland, Oregon—For years the Army Corps of Engineers has been chewing over the best way to bring back endangered populations of salmon and steelhead along the Snake River. The most controversial proposal—embraced by environmentalists and bitterly resisted by many local residents—is to breach four hydropower dams on the Snake River, a tributary of the Columbia River in Idaho and Washington state. At a press conference here on 17 December, the corps announced, to the dismay of both sides, that it was delaying a decision until summer.

    Describing the evidence as “not conclusive,” Brigadier General Carl Strock, commander of the corps's Northwestern Division, argued that the economic and social impacts of breaching the dams are so enormous that the corps needs “additional regional dialogue and scientific information” to “arrive at a preferred alternative.” As a basis for this discussion, the corps has released its draft environmental impact statement: megabytes upon megabytes on everything from salmon growth rates to analyses of tribal treaties (

    The delay does not sit well with tribes and environmental groups. Fanning their displeasure, the U.S. Fish and Wildlife Service (FWS) issued a report on the same day asserting that dam breaching “would provide many more benefits to fish and wildlife” than would other options. The “biological conclusion is a no-brainer,” says FWS regional administrator Anne Badgley. “A free-flowing river is better than a dammed river.”

    However, the corps will turn first for advice not to FWS, but to another agency—the National Marine Fisheries Service (NMFS)—which under the Endangered Species Act has the legal mandate to protect endangered migratory fish throughout the Columbia River Basin. Unsatisfied by the prospect of planning tributary by tributary, the NMFS wants to incorporate the recovery of Snake River fish into a basinwide effort. For that reason, says NMFS regional administrator Will Stelle, the agency is examining a “much more complicated” subject than Snake dams versus no Snake dams: the effects on endangered fish throughout the region of habitat degradation, hatcheries, and fishing, in addition to hydropower.

    The examination is occurring through a broad new NMFS program called the Cumulative Risk Initiative. CRI—which attempts to integrate the factors determining the species' risk of extinction into a model of population growth—supersedes an effort known as the Plan for Analyzing and Testing Hypotheses, or PATH (Science, 23 April, p. 574). PATH was intended to be the sole scientific basis for a Snake River decision, until NMFS concluded that independent scientists would get lost in PATH's complexity.

    Using the more transparent CRI model, Stelle says, NMFS scientists have finished an analysis of improvements that might help the Snake River salmon recover. The next step, he says, is to rate each option's feasibility. If what's best for the salmon were the sole criterion for decision-making, Stelle admits, “we should stop all irrigation, terminate all development and inriver uses, take out the dams, and probably move east.” But economic and social factors—not just what's best for the salmon—must be considered, NMFS recognizes.

    Next summer, after the CRI is finished, the corps will identify its “preferred alternative” in a revised draft environmental statement. The final version is expected late in 2000. If the corps endorses dam breaching, the matter will go to Congress for a final decision—suggesting that the resolution on the fate of these controversial fish is a long way off.


    Archaeology in the Holy Land

    1. Michael Balter

    Archaeologists in Israel and Palestine try to focus on science, but their work carries a heavy burden of expectation from religious leaders, biblical scholars, and local people eager to prove their right to this land

    Jerusalem, TelAviv, AndBeersheva—A few years ago, just before Israel turned most of the West Bank city of Hebron over to Palestinian control, an Israeli television station asked Tel Aviv University archaeologist Israel Finkelstein to come to the town and tape an interview in front of the Tomb of the Patriarchs. A large group of militant Jewish settlers was refusing to leave Hebron. One of their arguments was that because the biblical patriarchs Abraham, Isaac, and Jacob were buried in the tomb, Hebron was part of the Jewish heritage and thus Jews had the right to live anywhere in the city. Finkelstein explained that in his opinion the patriarchs were not real historical figures and that the tomb buildings were actually built during the reign of the Jewish king Herod the Great, more than 1000 years after Abraham and his kin supposedly lived. “The interviewer then turned to a rabbi from one of the settlements whom they had brought along and asked what he had to say,” Finkelstein recalls. “The rabbi said, ‘So what do I care if the patriarchs aren't historical? For me it's enough that the Jews have been here for the past 2000 years.’”

    The story illustrates the political sensitivities that many Israeli archaeologists have to contend with every day. As excavators in the Holy Land, they work in a region sacred to Jews, Muslims, and Christians. There is probably no other area of the world where archaeology carries such a heavy load of religious and political implications as in Israel and the occupied territories of the West Bank and Gaza Strip, which together make up much of ancient Palestine. Within Israel, archaeologists often run into conflicts with religious leaders, not only over their interpretations of archaeological evidence but sometimes over their very right to excavate sites containing human remains (see p. 34). And on the larger geopolitical scale, archaeology in this region has obvious connotations for Middle East politics. The unearthing in recent decades of evidence for early Israelite occupation has made many Israelis wildly enthusiastic about archaeological discoveries and intensified their feelings that they have priority in this land over the counterclaims of Palestinian Arabs.

    But as the history of the Middle East in this century has all too painfully demonstrated, the Israelis are not alone in making claims to this soil. And as the Palestinians, in the wake of territorial concessions by Israel, begin launching their own excavations in Gaza and the West Bank, a new generation of Palestinian archaeologists is now wrestling with the issue of how much to allow political and religious considerations to influence their own work (see p. 33). “People come here looking for their roots,” says Finkelstein, “and archaeology is the conduit.”

    Despite the ramifications their work might have for Middle East politics or religious faith, however, most Israeli archaeologists have tried to insulate their studies from political and religious influences. This doesn't mean that they have chosen to ignore the considerable remains left by the Israelites, Canaanites, and Philistines whose exploits fill the pages of the Bible—indeed, some of the biggest digs currently under way in Israel are at prominent biblical sites, such as the Philistine port city of Ashkelon (Science, 2 July, p. 36) and Megiddo in northern Israel, a supposed stronghold of King Solomon (see p. 31). But few Israeli archaeologists today would characterize their primary research concerns as proving that Jews have the right to live here or that the biblical stories are literally true. For the most part, archaeologists here employ the same scientific methodology and pursue the same types of research questions—such as settlement patterns, trade and economy, and daily details of ancient life—as their colleagues in other countries.

    And contrary to the impression created by the worldwide attention often generated by excavations of biblical sites, most digs here do not concentrate on the biblical period. The great majority of the roughly 200 excavations undertaken here each year are focused on epochs before or after the Bronze and Iron Ages, the respective periods in which Canaanite and Israelite settlements of Palestine are assumed to have taken root. To some extent, this is due to the large number of rescue excavations, most often of Byzantine and Roman sites, which are made necessary by Israel's continuing construction boom. Israel is also a major center of prehistoric research. Over the past 2 decades, Israeli prehistorians have uncovered tantalizing evidence—at sites such as the caves of Mount Carmel and those in the Jordan River Valley—that the Levant may have been a major corridor for movement of early humans out of Africa. And ongoing excavations at Sha'ar Hagolan, just south of the Sea of Galilee, have uncovered one of the Near East's largest Neolithic settlements, which was a center of extraordinary artistic activity (see p. 35).

    But, try as they might to distance themselves from religious influences, many of Israel's leading archaeologists have recently been caught up in new and sometimes fractious debates over the proper relationship between archaeology and biblical scholarship. They have come under attack from a group of European biblical scholars called “biblical minimalists,” who assert that figures such as Kings David and Solomon may never have existed and that the sprawling Israelite kingdom, with its capital in Jerusalem, they are supposed to have ruled was not a historical reality. These scholars have taken archaeologists to task for being guided too much by the Bible in their research (see next story).

    To some archaeologists, this controversy is regrettable. “We fought so hard to make archaeology here a respectable discipline and to free it from these kinds of emotional issues,” says William Dever, an archaeologist at the University of Arizona in Tucson. “And now we are back in the middle of it again.” Yet it may just be that, when excavating in the Holy Land, politics and the Bible simply go with the territory. “The power of religious and nationalistic symbols should not be underestimated,” says Steven Rosen, an archaeologist at Ben-Gurion University in Beersheva. “They will continue to play a role in Israeli archaeology, just as they do in most archaeologies around the world.”


    Baedeker's Guide, or Just Plain 'Trouble'?

    1. Michael Balter

    Despite efforts to focus on scientific questions, excavators in the Holy Land continue to be embroiled in debates on the Bible's historical value

    JerusalemAndTelAviv—Once upon a time, a great wise king named Solomon ruled over Israel. The wealth and power of his kingdom knew no equal. He built massive fortifications at strategic cities such as Megiddo, Hazor, and Gezer and raised up an enormous gold-laden temple at Jerusalem. Solomon had at least 700 wives and 300 concubines, including a pharaoh's daughter, and carried on a brief dalliance with the Queen of Sheba. As for his legendary wisdom, “All the kings of the earth sought the presence of Solomon to hear his wisdom, which God had put into his mind.” How do we know? The Bible tells us so. Unfortunately, however, there is no other direct evidence that this great king ever lived. Biblical scholars have dated Solomon's reign to the 10th century B.C. But if the Egyptians were aware of this mighty ruler on their eastern flank, they did not mention him in any of their numerous surviving 10th century inscriptions. Despite more than 150 years of archaeological excavations in the Holy Land, no trace of Solomon has ever been unearthed.

    This and other contradictions between what the biblical texts say and what excavators have dug up has made most archaeologists working here wary of using the Bible as any kind of field guide. In fact, over recent decades archaeologists in Israel have been steadily shifting away from answering questions posed by the Bible to questions of trade and economy, technology, and social issues in ancient societies. On the other hand, it is hard for archaeologists to ignore the Bible as a historical text. Jerusalem, Jericho, Bethlehem, Hebron, Gaza, Ashkelon—all of these modern cities were also backdrops for vivid episodes in the Old and New Testaments, and all contain traces of those ancient times. And now, despite years of trying to keep the Bible at arm's length, archaeologists find themselves on the other side of the argument, accused by a new school of biblical scholars of having become biased by the holy book. The result has been a lively and sometimes acrimonious debate among, and between, archaeologists and biblical scholars. Some argue that archaeology and biblical studies should divorce completely and go their separate ways. Others counter that such a drastic step would cut archaeologists off from one of the few historical sources they have.

    The Bible and the spade

    Although archaeologists working in Israel today struggle to keep their distance from religious and political questions, that has not always been the case. Until the mid-20th century, most major excavations in Palestine were carried out by Christian scholars out to prove the biblical stories were literally true or at least to put them into a historical context. Foremost among them was the American William F. Albright, who worked in Palestine in the 1920s and 1930s and whose name is most closely associated with what came to be called “biblical archaeology.” With the establishment of Israel in 1948, archaeology in Palestine took on a distinctly nationalistic form. The first generation of Israeli archaeologists, many of whom were ardent Zionists, began digging up ancient Israelite sites with feverish enthusiasm. The most prominent of these pioneers, the late Yigael Yadin—the commander of Jewish forces during the Israeli war of independence, who later became a professor of archaeology at Hebrew University in Jerusalem—pursued an explicit agenda of searching for Jewish roots in Palestine. In the 1950s and 1960s, Yadin excavated ancient sites such as Hazor and Masada (site of the Jewish zealots' last stand against the Romans) with, as he once put it, “the Bible in one hand and the spade in the other.”

    But beginning in the 1970s, a new generation of Israeli archaeologists began to emerge. Having grown up in a country now more confident about its permanent survival despite ongoing Arab hostility, and influenced by advances in archaeological science in the United States and Europe, these excavators were much less inclined to allow religious or nationalistic concerns to determine their research directions. “Israeli archaeology has moved considerably beyond the Bible and the spade,” comments Steven Rosen, an archaeologist at Ben-Gurion University in Beersheva. “It would be a rare Israeli excavation today that would include the Bible as a reference book in its dig house.” And William Dever, an archaeologist at the University of Arizona in Tucson who is widely regarded as one of the pioneers of scientific archaeology in Palestine, declares: “We wrote the obituary for biblical archaeology, and nobody mourns its passing today.”

    The Bible as history?

    But debate over the influence of the Bible on archaeology was not quite dead. It was brought to life again in 1992 with the publication of a book by Philip Davies, a biblical scholar at the University of Sheffield in the United Kingdom, entitled In Search of “Ancient Israel.” Davies, one of the leading lights in a group often dubbed “biblical minimalists,” argued that the so-called United Monarchy founded by King David, and greatly expanded by his son Solomon, is a literary invention by biblical authors writing hundreds of years after the purported events and is not reflected in the archaeological record. Davies contended that there is no more archaeological evidence for the reign of David and Solomon than for Adam and Eve or Noah and his Ark. Most provocatively, Davies suggested that without the influence of the Bible, archaeologists might never have identified any of their findings from the 10th century B.C. as belonging to an early state called Israel. In other words, Davies claimed, the unreliable biblical texts were introducing a major bias into archaeological interpretation.

    Davies's book—along with similar arguments by University of Copenhagen biblical scholar Thomas Thompson and others—has triggered heated debates among archaeologists. “This book is what started the whole thing,” says Arizona's Dever. At issue is the extent to which archaeologists should attempt to correlate what they dig up in excavations with the biblical texts, if at all. Tel Aviv University archaeologist Israel Finkelstein, who says he regularly assigns Davies's book to his students, comments that the minimalist position represents the latest phase in “a gradual pullback, a withdrawal from considering the biblical texts as historical. The question is where to stop—that is what the debate is about.”

    Many archaeologists say the minimalists have already gone too far. Amihai Mazar, an archaeologist at Hebrew University in Jerusalem, believes that if the Bible is jettisoned, “we would have to dump into the garbage pile all the scholarly literature of the last 100 years relating the Bible to archaeology and vice versa.” Mazar and others argue, for example, that Solomon's glorious reign cannot be completely dismissed as biblical mythology. The locations of Megiddo, Hazor, and Gezer have been identified with a high degree of confidence. And Egyptian, Assyrian, and Babylonian inscriptions mention a number of Solomon's royal successors.

    Moreover, in 1993, at a site identified as the biblical city of Dan in northern Israel, archaeologists dug up an inscription referring to the “House of David.” After years of fierce debate among archaeologists and biblical scholars over the significance of this inscription, most doubters have now conceded that some sort of dynasty founded by a king named David existed here in ancient times, even though they still don't believe this dynasty had anywhere near the grandeur described in the Bible.

    Other archaeologists, however, believe the minimalists have some valid points. “We have to completely separate biblical research on one hand and archaeology on the other,” says Tel Aviv University archaeologist David Ussishkin. Together with Finkelstein, Ussishkin has recently concluded that monumental architecture at Megiddo and other sites attributed to Solomon and interpreted as evidence for the United Monarchy dates from later periods—research that is often cited by the minimalists as support for their position (see p. 31).

    Archaeologists working in the Holy Land are now struggling to define a middle way. “There are those who see the Bible as a religious document and nothing but trouble,” says Dever. “But you must take the biblical texts as seriously as you would any other text. The Bible is the most extensive literary source for the Iron Age in Palestine, so the question is not whether to use it, but how.” Finkelstein, despite his sympathy with some of the minimalists' points, agrees: “In the more enlightened circles of biblical studies, there is a deep knowledge that the Bible is composed from different sources written at different dates and was edited and reedited many times. And yet I consider some of the biblical material to be historical writing,” he says. “People say, ‘How can you trust some parts of it and not others?’ But that is what we should be doing, sorting out what is history and what is not.”


    The Two Tels: Armageddon For Biblical Archaeology?

    1. Michael Balter

    A proposed revision of the dating of remains in Israel challenges the Bible's depiction of a powerful state ruled by Kings David and Solomon

    TelMegiddoAndTelRehov—Archaeologist David Ussishkin pauses on the path near the top of a sprawling mound overlooking the green fields of Israel's Jezreel Valley. It is just after 9:00 a.m., but the summer heat is already blistering. Beneath Ussishkin's feet lies a layer cake of consecutive settlement levels dating back more than 6000 years. During the Bronze and Iron Ages, which in the Levant stretched roughly from 3300 B.C. to 600 B.C., this artificial hill was the site of Megiddo, a city occupied successively by Egyptians, Canaanites, Israelites, Assyrians, and Persians. According to the Bible, Megiddo was one of the northern strongholds of the Israelite king Solomon and will be the site of the final battle between God and his enemies when time comes to an end—Armageddon is derived from the Hebrew “Mount of Megiddo.”

    Just off the path stands a massive stone gate that once marked the entrance to the city. A sign placed in front of it by Israeli tourist authorities reads “Solomonic gate, 970-930 B.C.” Ussishkin looks at it and laughs. “This is nonsense, utter nonsense,” he tells a visitor. “The gate is from 200 years later. Solomon must be turning in his grave.” For the past several years, Ussishkin, along with fellow Tel Aviv University archaeologist Israel Finkelstein and Near Eastern historian Baruch Halpern of Pennsylvania State University, University Park, has been co-directing an extensive dig at Megiddo. And some of the findings have set off a battle among archaeologists working in Israel. At issue is whether the biblical picture of a major Israelite state in Palestine, founded by King David and greatly expanded by Solomon, reflects the historical reality of Israelite settlement in this region.

    Finkelstein, in particular, has concluded that the conventional dating of certain occupation levels at Megiddo is incorrect. He argues that levels previously dated to the 10th century B.C., when many biblical scholars and archaeologists assume that David and Solomon ruled, should be moved later, to the 9th century B.C. This adjustment, which some archaeologists have dubbed the “Finkelstein correction,” would imply that massive fortifications and stone palaces at Megiddo previously attributed to Solomon's reign might really have been the work of a later ruler, such as the 9th century's King Ahab. David and Solomon may have simply been tribal chiefs from early- or pre-kingdom days whose reputations were greatly aggrandized by the biblical authors, who wrote their texts hundreds of years after the events they describe; or they may never have existed at all, as suggested by some scholars called the “biblical minimalists” (see p. 29).

    The debate, which touches on the politically sensitive issue of Jewish roots in Palestine, has been followed with keen interest by archaeologists and other scholars who work in the region. So far, Finkelstein—along with Ussishkin, who agrees with him on many points but reserves judgment on others—appears to be in the minority. One leading opponent of the Finkelstein correction is archaeologist Amihai Mazar at Hebrew University in Jerusalem, who is leading excavations at Tel Rehov, south of the Sea of Galilee, that he believes contradict Finkelstein's thesis. At times the controversy has become very heated. “For archaeologists working in the biblical era, the issues are central to how one views this period,” says archaeologist Steven Rosen of the Ben-Gurion University in Beersheva. “And for the public interested in biblical archaeology, it affects central matters of faith.” One archaeologist recently charged in the press that Finkelstein was providing a “fig leaf to the anti-Semites” by downgrading David and Solomon. And Finkelstein, in a debate with Mazar over the issue in the journal Levant, accused Mazar of harboring a “sentimental, somewhat romantic approach to the archaeology of the Iron Age.”

    The controversy swirls around complex and often esoteric archaeological issues involving pottery, stratigraphic analysis, and the correlation of burned occupation levels with historical events such as the sacking of cities in ancient Palestine by Egyptians and Assyrians. The problem arises from the fact that for roughly 450 years, during which the two Israelite kingdoms of Israel and Judah were supposedly in their glory days, archaeologists in Palestine have no firm chronological guideposts. This period is anchored at either end by two firmly dated events: a battle fought in 1175 B.C. between the Egyptians and Mediterranean raiders called the Sea Peoples during the reign of Ramses III, recorded in detailed Egyptian inscriptions that are also linked to many historical and astronomical events; and detailed records left by the Assyrians—chronologically anchored to an eclipse in 763 B.C.—which recount campaigns against the Israelites and other inhabitants of Palestine in the late 8th century B.C.

    There was, however, one well-dated event in the region during this period: Egyptian Pharaoh Shoshenq I's invasion of Palestine, reckoned from Egyptian records at about 926 B.C. Yet this event, which the Bible says took place 5 years after Solomon's death, has been of limited help, because archaeologists do not always agree about which of the numerous destruction levels at Megiddo and the other cities Shoshenq attacked were his doing.

    Hence, the most common method archaeologists use to date strata in this period is by the pottery they contain, an approach Finkelstein thinks needs adjustment. In particular, Finkelstein contests the traditional view that shortly after their 1175 B.C. battle with Ramses III, one group of the Sea Peoples, the Philistines, quickly settled on and near the coast of present-day Israel (Science, 2 July, p. 36) and began manufacturing a characteristic style of pottery called monochrome. The presence of this pottery has been taken as a marker for remains from the 12th century B.C., while a later style of Philistine pottery, called bichrome, is usually attributed to the 11th century.

    Finkelstein argues, based on his reinterpretation of Egyptian inscriptions and other evidence, that the Sea Peoples did not begin settling down until 40 or more years after the 1175 B.C. battle. This shift, he says, would mean that the conventionally accepted dating of the monochrome and bichrome pottery puts it too early. One of his key arguments is the absence of monochrome pottery in excavations of Egyptian settlements that remained in Palestine after 1175 B.C. Given the promiscuous nature of pottery exchanges between settlements in the Near East, Finkelstein contends that it is inconceivable that these cities—some just a handful of kilometers from known Philistine settlements—would not have traded with them. As a result, Finkelstein says, the key Philistine sites used for dating the monochrome pottery could not have been established until after Egyptian domination in Palestine totally collapsed in the late 12th century B.C˙˙

    And this redating of the monochrome pottery, Finkelstein concludes, shifts the chronological guideposts, pushing the long-lived bichrome style—which replaced the monochrome pottery—into the late 11th and much of the 10th century B.C., and archaeological strata and pottery conventionally dated to the 10th century—the supposed era of David and Solomon—down into the 9th century B.C. As additional support for this idea, both Finkelstein and Ussishkin have concluded from a reanalysis of the stratigraphy of the stone gate at Megiddo, which earlier excavators had identified as Solomonic, that even under the conventional chronology it was built a century later. The Finkelstein correction would make it yet another 100 years later still.

    Finally, Finkelstein and Ussishkin cite recent excavations in Jerusalem that have failed to find any evidence of large-scale building in the 10th century B.C.—despite the Bible's account that David established his capital there and that Solomon built an enormous temple in the city. “There is a very big problem for the traditional [dating] in Jerusalem,” says archaeologist Gideon Avni of the Israel Antiquities Authority. “We have very minimal remains from both the 10th and 9th centuries B.C.”

    But many other archaeologists believe that Finkelstein has not proven his case for altering the conventional chronology. For example, Seymour Gitin, director of the W. F. Albright Institute of Archaeological Research in Jerusalem, contests Finkelstein's assumption that pottery was necessarily exchanged between neighboring contemporaneous sites. Gitin, who co-directed excavations at the Philistine site of Ekron, says that no monochrome pottery has been found at Gezer, a nearby Canaanite city widely agreed to have existed at the same time. “Not one shard representing early Philistine culture has been found at Gezer,” Gitin says. “How do you explain that?”

    And William Dever, an archaeologist at the University of Arizona in Tucson, who excavated Gezer—and unearthed a stone gate of similar design to that found at Megiddo, which he has dated to the 10th century based on the conventional pottery scheme—says that Finkelstein is “way out on a limb” with his chronological correction. “If anyone can prove to me this material is all 9th century B.C. and no Solomon ever lived, I don't care. But proof please, gentlemen, proof please!”

    Dever adds that Finkelstein has given short shrift to the circumstantial evidence left by the invasion of Shoshenq I in about 926 B.C., which he believes supports the conventional view. Egyptian inscriptions list more than 100 cities that Shoshenq supposedly conquered—including Megiddo and Gezer. Excavations of more than 25 sites on the list have identified destruction layers that many archaeologists attribute to Shoshenq's invasion. Moreover, there is a characteristic difference in pottery styles—a shift from a hand-burnished to a wheel-burnished finish—in settlements built before and after these destruction layers. Dever and other archaeologists believe this hand-burnished pottery provides a chronological marker for the 10th century B.C. Finkelstein, on the other hand, disagrees, arguing that many of the destruction layers usually attributed to Shoshenq should be blamed on later 9th century B.C. invaders.

    Mazar says that his ongoing excavations at Tel Rehov, another site on Shoshenq's list, support the conventional dating scheme. Although radiocarbon dating of the Iron Age period can be treacherous, due to the wide margins of error involved, short-lived grains of wheat, barley, and other plants can often be dated with reasonable accuracy. At Tel Rehov there is a major destruction layer associated with hand-burnished pottery. Radiocarbon dating of charred grains from this layer, which Mazar believes corresponds to the Shoshenq invasion, gave dates ranging from about 916 to 832 B.C. The older end of this range, at least, correlates reasonably well with the timing of Shoshenq's raid, although the later date would not. But radiocarbon dates from the beam of an elm tree used in the construction of this occupation level came in at 1120 to 990 B.C. This means, Mazar told Science, that even if Shoshenq did not destroy this settlement, it was constructed no later than the 10th century B.C., and the hand-burnished pottery found with it is rightly “diagnostic” of the pre-Shoshenq period.

    “I have no doubt that the description of David and Solomon in the Bible is to a large extent exaggerated,” says Mazar. “But this doesn't mean you have to cancel David and Solomon as historical figures.” Finkelstein agrees that even if his hypothesis is correct, it “does not mean that David and Solomon did not exist.” On the other hand, he adds, the nature of their realm “was very different” from that assumed by many archaeologists and biblical scholars. Rather than making up a full-blown state, he believes, the early Israelites may have formed a much smaller political entity and been restricted to a much smaller territory than indicated in the Bible. The biblical writers “told the story the way they wanted to tell it,” says Finkelstein. But if his correction is right, he concludes, “you would have to write a new history of the Levant, of Israel, and of the Eastern Mediterranean in the Iron Age.”


    Palestinians Inherit Riches, But Struggle to Make a Mark

    1. Michael Balter

    Denied for 3 decades the right to dig in their own land, Palestinian archaeologists are now only held back by a lack of cash and training

    WestBankAndGazaStrip, Palestine—Khirbet Siya, a craggy mound nestled among austere orange hills near the West Bank town of Birzeit, might not seem the most auspicious site for an archaeological dig. What remains of a Byzantine village has been badly scarred by looters, who over the years have eaten away at the mound looking for ancient treasures. But for Hamed Salem of the Palestinian Institute of Archaeology in Birzeit, it is an opportunity he had been waiting for since the early 1980s. Last July, with the aid of students from Birzeit University, the United States, and Europe, Salem began excavating at Khirbet Siya—the first dig he has directed since becoming an archaeologist nearly 20 years ago. Among the discoveries are a giant olive press and traces of one of the oldest Byzantine churches ever found in Palestine.

    Until 5 years ago, when Israel began ceding parts of the territories occupied during the 1967 Arab-Israeli War to the Palestinians, local archaeologists were rarely allowed to excavate in the West Bank and Gaza, which were under military jurisdiction. But after the creation of the Palestinian National Authority (PNA) in 1994, Palestinians soon found themselves in possession of thousands of archaeological sites. Many are of major importance, such as Tel es-Sultan in Jericho and Deir el-Balah south of Gaza City, which during past excavations have revealed important insights into the Neolithic and Bronze Age peoples that once inhabited this land. For Palestinian archaeologists, this sudden embarrassment of ancient riches is both a blessing and a curse: Although they are thrilled at the chance to dig at last in their own land, lack of funding and trained excavators means they can often do little more than protect and preserve the sites from falling into ruin or the clutches of looters.

    “We are starting completely from scratch,” says archaeologist Adel Yahya, director of the Palestinian Association for Cultural Exchange. And as Palestinian archaeologists enjoy their newfound freedom, they are struggling to define their own research priorities and to avoid allowing archaeology to serve political and religious ideologies—a trap many of them believe Israeli archaeologists often fell into (see p. 29).

    Their first priority is money. The Palestinian Department of Antiquities based in Ramallah—which was also created in 1994—currently receives only $500,000 annually from the PNA, according to department chief Hamdan Taha. And although contributions from outside donor countries, such as the Netherlands and Italy, have swollen the total department budget to several million dollars each year, nearly all of this money goes into restoring and protecting archaeological sites rather than research. “The major task of the department is rescue archaeology,” says Taha. “Many sites were left as they were in 1967, and others have been excavated and then abandoned. Thousands of sites have been plundered and looted.”

    The lack of funds for research digs is very unfortunate, archaeologists say, because the thousands of sites now under Palestinian control represent a treasure trove of potential new information. “This is one of the richest archaeological areas in the world,” says Joanne Clarke, director of the Jerusalem office of the Council for British Research in the Levant. This is especially true of the Gaza Strip, a major crossroads of the ancient Near East. And yet, Clarke says, the Gaza area “is almost completely untouched” by archaeologists. Clarke and the council are now teaming up with Palestinian antiquities authorities to excavate a number of Bronze Age settlements in Gaza, which were home to the Egyptians, Philistines, and Canaanites who vied for control of this region in ancient times.

    Like the Gaza project, nearly all research digs currently under way here—such as new excavations by an Italian-Palestinian team at Jericho and Dutch-Palestinian explorations of an extensive Canaanite water system at Khirbet Belameh, near the West Bank city of Jenin—rely heavily on foreign funds and expertise. But this dependence on outside help worries many Palestinian archaeologists. Khaled Nashef, director of the Palestinian Institute of Archaeology, for example, complains that over the decades foreign archaeologists have dug in Palestine and then gone away, publishing their findings in their own languages without translating them into Arabic. “We need to work with foreign archaeologists as equal partners, but it is not easy.”

    One fundamental obstacle to getting Palestinian archaeology off the ground is a severe lack of opportunities for students wanting to enter the field. Nearly all of the archaeologists in Palestine—who number, according to various estimates given to Science, between 15 and 25 with graduate degrees—were trained in other countries. The only institution that currently offers graduate-level training in archaeology is the Institute for Islamic Archaeology near Ramallah, which awards masters' degrees. The Palestinian Institute of Archaeology, which is part of Birzeit University and once also offered masters' degrees, suffered a major setback when its American director was murdered under mysterious circumstances in 1992. Today, it only offers an undergraduate minor in archaeology, although Nashef—who took over the rudderless institute in 1994—says he hopes to convince university administrators to restore at least a major in the subject soon.

    As they wrestle with these legacies of the recent past, many Palestinian archaeologists express a strong desire to keep ideological and religious issues out of their nascent archaeological endeavors. This may prove difficult, because there is considerable evidence that the Palestinian general public—which is well aware that Israeli archaeology has often been linked with the search for Jewish roots in Palestine—appears hungry for archaeological discoveries that would prove that the Palestinians were here first. Over the past few years, a number of articles have appeared in Palestinian newspapers and magazines—and even on the PNA's Web site—claiming that Palestinians were descended from the Canaanites or other pre-Israelite residents of Palestine. In discussions with Science, most Palestinian archaeologists were quick to distance themselves from these ideas.

    “We don't want to repeat the mistakes the Israelis made,” says Moain Sadek, head of the Department of Antiquities' operations in the Gaza Strip. Taha agrees: “All these controversies about historical rights, who came first and who came second, this is all rooted in ideology. It has nothing to do with archaeology.” But not all archaeologists here believe that issues of Palestinian national identity can be totally shunted aside. “This question cannot be avoided,” says Nashef. “Until now we Palestinians have not worked to create our own history, and this is our own fault. Archaeology here has concentrated on historical events or figures important to European or Western tradition. This may be important, but it doesn't provide a complete picture of how local people lived here in ancient times.”

    Until Palestinian archaeologists can develop the basic infrastructure needed to conduct excavations, these thorny ideological issues will probably remain largely academic. In the meantime, they will be concentrating on constructing their budding discipline from the ground up. “We have the core human resources,” says Mahmoud Hawari, an archaeologist who teaches at the Institute for Islamic Archaeology. “Now we just need to get ourselves together. It might be a gradual evolution, but it is no shame to start small.”

  11. Artifacts Prompt Tug-of-War

    1. Michael Balter

    Now that the Palestinians finally have control over their archaeological heritage, they are furious over Israel's refusal so far to return the countless artifacts—pottery, grave goods, inscriptions, jewelry, and so on—that were uncovered during Israeli excavations in the occupied territories over the past 3 decades. This refusal, they argue, is against The Hague Convention of 1954, which they believe prohibits excavations in captured territory by an occupying nation. During peace talks between Palestinians and Israelis since the Oslo Accords of 1993, Palestinian negotiators have brought up this issue repeatedly, only to be rebuffed. “We were prevented from excavating here, we were prevented from visiting archaeological digs, and now all the artifacts have been exported to Israeli museums,” says Moain Sadek, head of the Department of Antiquities' operations in the Gaza Strip, who together with department chief Hamdan Taha has been involved in direct negotiations with the Israelis on the issue.

    But the Israelis counter that The Hague Convention does not apply to the West Bank and Gaza, because these territories—which came under Jordanian and Egyptian administration after the Israeli war of independence in 1948—were not part of any nation at the time the convention was signed. “Should we give the Dead Sea scrolls to Arafat?” asks Amir Drori, director-general of the Israel Antiquities Authority, who at times has sat at the same negotiating table with Taha and Sadek. “When we made peace with Egypt, we returned all artifacts we found in the Sinai. And if we make peace with Syria and return the Golan Heights, we will have to follow The Hague Convention there as well. But the picture is not the same in [the West Bank] and Gaza. No one knows who was the legal ruler there—Israel, Jordan, Egypt, the British under the mandate, or the Ottoman Turks.”


    Archaeologists and Rabbis Clash Over Human Remains

    1. Michael Balter

    Because of the influence of religious leaders in Israel, human remains cannot be studied and excavators face continual attacks from fundamentalists

    JerusalemAndTelAviv—Patricia Smith, a physical anthropologist at Hebrew University in Jerusalem, and a group of co-workers published a paper 4 years ago in the journal Gene describing a new genetic technique for determining the sex of human remains unearthed in ancient burials. The technique—which relies on a small difference between the X and Y chromosomes in the gene coding for amelogenin, a protein important in the formation of tooth enamel—looked promising for studying bone fragments or the remains of children, whose sex is very difficult to determine even from complete skeletons. Indeed, when Smith and her colleagues applied the test to fragments of DNA extracted from tooth and bone samples from Israeli archaeological sites ranging from 200 to 8000 years old, the team was able to determine unambiguously the sex of 18 out of 22 of them, including young children.

    The amelogenin test could help shed light on the family relations and other gender-related issues in ancient societies across the world. But in Israel, the country where it was devised and which has a wealth of archaeological remains, the technique can no longer be used legally. Neither can any of the other scientific techniques anthropologists routinely bring to human remains unearthed in archaeological digs. The reason: In 1994, in the wake of protests by ultra-Orthodox Jewish leaders against disturbing ancient graves, Israel's attorney general ruled that any human remains must immediately be handed over to the ministry of religious affairs for reburial. But even this measure has not satisfied some ultra-Orthodox groups, which today continue to mount violent demonstrations against digs that might uncover human bones, even when they are unlikely to be the remains of Jews or Israelites.

    “Physical anthropology is no longer carried out at Israeli excavations,” says Amir Drori, director-general of the Israel Antiquities Authority (IAA). And archaeologists here say the result is a great loss of important information—including data about the transition from Canaanite to Israelite settlement in Palestine. “We were beginning to understand the longevity of the Canaanite populations in this region, the extent of in-group and outgroup marriages, and the mechanisms of population shifts over different time periods,” says Arlene Rosen, an archaeologist at University College London who worked in Israel for many years. “Now all this research has come to a halt.”

    In 1998, in an attempt to calm the situation, the Israeli government appointed five Orthodox rabbis to the nation's Archaeological Council, a 38-member body of archaeologists and other experts that advises the IAA on granting excavation permits. Unlike the ultra-Orthodox activists, who argue that any disturbing of burial sites goes against Jewish law, Israel's Orthodox rabbis have generally agreed that bones can be removed so that digs can go on. But they still insist that they must be reburied without being studied. But this attempt at a compromise has not stopped the demonstrations. Last June, for example, an altercation between demonstrators and an archaeological team conducting a rescue dig at a construction site near the Ben Shemen interchange in central Israel prompted the police to shut down the dig temporarily and arrest two of the archaeologists. “When a bulldozer hits a grave, what do they want us to do?” says Moshe Kochavi, an archaeologist at Tel Aviv University and chair of the Archaeological Council. “We can let the bulldozer destroy the grave, or we can let the archaeologists dig it.” But Smith says that whatever their objections to disturbing Jewish remains, the religious leaders should have no say about what happens to non-Jewish remains: “What right do they have to assume authority over Phoenician, Canaanite, Bronze Age, or prehistoric peoples?”

    But ultra-Orthodox leaders see things differently. “We have nothing against archaeology per se,” says Rabbi David Schmidl, a leader of Atra Kadisha (“Holy Sites”), one of the main groups involved in organizing the protests. On the other hand, he told Science, according to Jewish law “it is forbidden to disturb the rest of these bodies. It angers the soul.” Schmidl compares the controversy in Israel to the debates in North America between archaeologists and Native American activists, who have insisted on the return of Native American remains so they can be reburied (Science, 26 February, p. 1239). As for non-Jewish graves, Schmidl says, “it is a little less problematic to move the bones, but any grave deserves the proper honor.”

    Archaeologists and anthropologists had hoped that the new government of Prime Minister Ehud Barak would be more sympathetic. So far, however, the government has not shown any sign of making this a priority issue. “For politicians, it is a very minor issue they can give way on,” says Smith. In the meantime, she adds, “a branch of science that has a major contribution to make is being stamped out.”


    Unearthing Monuments of the Yarmukians

    1. Michael Balter

    Despite the headline-grabbing biblical remains in this region, prehistorians are digging up a wealth of artifacts from earlier peoples

    KibbutzSha'arHagolan—For any visitor to Israel, the ruins of Megiddo and Hazor or the cobbled streets of Jerusalem are a vivid reminder that the Holy Land is sacred to three major religions. Yet hidden away in caves and fields, usually well off the tourist path, prehistorians have found plenty of evidence that this fabled land was a major crossroads of human civilization long before the biblical period. Over the past decade, in the fields of this kibbutz just south of the Sea of Galilee, archaeologists have been excavating a splendid example: an 8000-year-old village built in stone that may have been the capital of the Yarmukians, one of the earliest Neolithic (New Stone Age) peoples to settle in modern-day Israel, Jordan, and Lebanon.

    In part, the 1990s dig has confirmed what earlier excavations here had shown: The Yarmukians were among the most talented artists of the Neolithic period, producing finely engraved pottery and beautiful, intricately carved figurines stunning enough to be displayed in art museums. Indeed, some of the more than 300 figurines unearthed here over the years were exhibited in New York City's Metropolitan Museum of Art last fall. But the excavations are also challenging the conventional view that the Yarmukians were seminomadic and pastoral, occupying their settlements only part of the year. Instead, the past few years of digging have uncovered the foundations of three monumental stone buildings, one of which measures 3200 square meters—one of the largest Neolithic structures ever discovered—as well as paved streets and alleys, all indications of a highly stable community.

    The Yarmukians were first discovered in the 1930s, when early Jewish settlers at this site near the banks of the Yarmuk River—a tributary of the river Jordan—began plowing up figurines and a characteristic type of elaborately decorated pottery. When this same pottery began showing up at other sites of similar age, such as early settlement levels at Megiddo in northern Israel and Byblos in Lebanon, it became clear that it represented an ancient culture that had spread fairly widely in the Near East. But excavations at Sha'ar Hagolan by Israeli archaeologists during the 1950s failed to uncover any monumental buildings. Instead, the earlier team concluded from various large pits they found that the Yarmukians had lived in circular huts half buried in the ground, which was consistent with findings at other Yarmukian sites.

    Thus the monumental buildings, which have been found only at Sha'ar Hagolan, might mean that this site had a special significance. “Sha'ar Hagolan might have been the territorial center” of Yarmukian culture, says archaeologist Yosef Garfinkel of the Hebrew University in Jerusalem, who is co-directing the excavations along with independent archaeologist Michele Miller of New York City. Garfinkel adds that the buildings, along with the well-defined streets and alleys, are evidence of highly organized communal activity. And Brian Hesse, an zooarchaeologist from the University of Alabama, Birmingham, who is studying the remains of animal bones here, says the dominant animal appears to be domesticated pig, with a “surprising” lack of fish and other aquatic animals even though the village was right next to a river.

    Garfinkel says he has no idea what the purpose of the monumental buildings was, although he hopes to uncover more evidence in the coming years of excavation. As for the figurines, he assumes—as do most archaeologists who study figurines from Near Eastern sites—that they served some sort of religious purpose. But whatever their meaning, Garfinkel adds, “these are the most beautiful figurines in the ancient Near East. A lot of energy and symbolic thinking went into making them.”

  14. A Crushing End for Our Galaxy

    1. Robert Irion

    The galactic mergers that help mold the Milky Way are mere fender benders compared to the mighty collision that promises to destroy it

    On Wall Street, mergers are a way of life. Big businesses gobble little ones with abandon, while giant corporations merge in multibillion-dollar megadeals. Little do the corporate sharks know that these banal feeding frenzies mimic far grander events in the universe, where large galaxies gently gulp smaller ones or smash into each other in cataclysms that spawn the titans of the cosmos.

    Despite its apparent calm, our Milky Way is not immune to this turmoil. Astronomers have long suspected that small clumps of stars and gas—the flotsam and jetsam of intergalactic space—rained down upon our infant galaxy to help build its structure. Now they are beginning to spy evidence of past mergers: stars that stream in lockstep, tracing the paths of long-vanished minigalaxies devoured by the Milky Way. Other mergers are taking place even now, as clouds of gas fall into our galaxy and a nearby dwarf galaxy is shredded by the Milky Way's intense tidal forces. And a few billion years from now—perhaps even before Earth is incinerated by our dying sun—looms our galaxy's brutal fate: a merger with M31, the Andromeda galaxy. That gigantic collision will leave behind a haphazard wrack of stars and dust.

    When telescopes began taking snapshots of collisions unfolding elsewhere in the universe, many astronomers viewed these events as the exception rather than the rule. But recent findings have erased most such doubts, says astronomer François Schweizer of the Carnegie Observatories in Pasadena, California. Indeed, violent encounters between spiral galaxies may have produced most of the bloblike elliptical galaxies in the universe today, he says. “Mergers are the major drivers of galactic evolution.”

    Let there be clumping

    Without mergers, the universe would be populated by dwarfs. Theorists believe that the first major objects that clumped together in the early universe held about 1/100,000th the mass of today's Milky Way. These galactic building blocks contained heavy dollops of dark matter—mysterious stuff that emits no light of its own—and perhaps the earliest generations of stars. In many regions of space, clumps formed close enough to each other for gravity to draw them into head-on collisions. This process continued within clusters of galaxies, creating a universe in which galaxies grow heftier with time.

    This notion of progressive clustering was appealing, but it took a stunning picture to drive it home: the Hubble Deep Field. That 1996 image from the Hubble Space Telescope revealed thousands of distant galaxies within a tiny patch of sky in the Northern Hemisphere, a glimpse of a time when the universe was as young as 10% of its current age. Most of the galaxies were not at all like the ones seen today. “The distant galaxies were smaller and more irregular, and they gave the visual impression that they were still forming,” says astronomer Leo Blitz of the University of California, Berkeley.

    The Milky Way is still under construction, it seems. In a talk next week at a meeting of the American Astronomical Society in Atlanta, Blitz will argue that curious patches of hydrogen gas seen all over the sky represent minigalaxies that continue to fall into the Milky Way and generate waves of star birth. Astronomers have known of these patches, called “high-velocity clouds,” since 1963, but no one has explained their origins or measured their distances from Earth. Blitz's team has used indirect lines of evidence to reason that they lie outside the galaxy, scattered throughout the Local Group, a loose knot of galaxies that encompasses the Milky Way, Andromeda, and numerous dwarfs. If so, they may be remnants of the first blobs that coalesced in the universe. Blitz believes that long telescope exposures may reveal stars within the clouds.

    However, astronomer Bart Wakker of the University of Wisconsin, Madison, feels Blitz is stretching his interpretations too far. Wakker and his colleagues reported in the 25 November issue of Nature that the largest known high-velocity cloud contains few heavy elements. That's just as one would expect if the cloud dated from the early universe. But Wakker observes that astronomers have not yet seen such hydrogen clouds in other galaxy groups, as should be the case in Blitz's scenario. Instead, he believes the clouds are remnants of gas torn from nearby dwarf galaxies that wandered near the Milky Way. Regardless of their origins, the clouds should merge with the Milky Way and replenish its hydrogen fuel supply at a pace sufficient to produce about one new star per year—roughly the observed rate, Wakker says.

    If it turns out that some of the clouds are minigalaxies, they may help solve a puzzle. According to models of how the early universe formed, the Local Group should include many more small satellite galaxies than are seen, says astrophysicist Anatoly Klypin of New Mexico State University in Las Cruces. The satellites should have arisen from the smallish lumps of dark matter that dominated the young cosmos. Although large galaxies probably absorbed most of those lumps within a few billion years, many hundreds of dim galaxies should survive in our cosmic neighborhood today, Klypin and several co-workers claim in the 1 September Astrophysical Journal. Instead, astronomers have found only about 40. The high-velocity clouds could make up part of the difference.

    The throng of nearby dwarfs should be dwindling slowly as they merge with the Milky Way, and astronomers may now be identifying traces of these collisions. Amina Helmi of Leiden University in the Netherlands and her colleagues studied data from the European Hipparcos satellite, which measured the motions of thousands of nearby stars. They found evidence for about a dozen stars moving at nearly identical clips and along similar paths through the tenuous but enormous spherical “halo” of stars girdling the galaxy's central bulge. “It's very unlikely to have that many stars comoving in the halo unless they had a common origin in a small galaxy that fell onto the Milky Way many billions of years ago,” says Helmi, whose findings appeared in the 4 November issue of Nature. According to astronomer Sidney van den Bergh of the Dominion Astrophysical Observatory in Victoria, British Columbia, the research jibes with a growing suspicion that the halo is a melting pot of “little bits and pieces that have accreted over time.”

    Although it may seem extraordinary that stars would preserve signatures of their original orbits so long after their parent galaxies disintegrated, simulations show that those tracers are feasible, says astrophysicist Joshua Barnes of the University of Hawaii, Honolulu. “My bet is that as we look farther, we'll be able to tease apart the entire halo as a collection of these star streams from past mergers,” he says. Help on this front may come from two planned NASA satellites—the Full-Sky Astrometric Mapping Explorer in 2004 (see sidebar) and the Space Interferometry Mission in 2006—which will greatly expand the number of stars with known orbits.

    However, analysis of the Milky Way's dynamics suggests that most major mergers must have happened before the galaxy formed its thin disk of stars and gas, which orbits the starry central bulge like a spinning Frisbee. Astronomers think the disk is too fragile for mergers to have contributed more than a few percent of its mass in the last 5 billion years. Otherwise, the disk would be severely distorted or puffed up from the gravitational eggbeater effects of incoming stars. Thus, it seems, “not much has happened” of late on the merger front, says astronomer Rosemary Wyse of The Johns Hopkins University in Baltimore, Maryland. “We may have continued to accrete little dwarf galaxies, but that's about it.”

    What giveth shape, taketh away

    That is not to say that the era of mergers is past. For evidence to the contrary, one need look no farther than the Sagittarius dwarf galaxy, a motley bunch of stars discovered in 1994. Nearly hidden behind the dense central regions of the Milky Way, the Sagittarius dwarf contains about 1000th the mass of our galaxy. Its orbit is not yet clearly defined, but it appears to loop around the Milky Way on a long, egg-shaped path. The Milky Way's tides are strong enough to rend the dwarf into a stretched-out shadow of its former self. New observations reveal a ribbon of about 10 stars along the dwarf's route that extends nearly around our galaxy, like a sinuous tail curving behind a diving kite. Presumably, those stars are “tidal debris” stripped from the dwarf during previous orbits, says astronomer Geraint Lewis of the University of Victoria in British Columbia.

    The dwarf's path may already have forced it to traverse the outer parts of the Milky Way's disk several times. Its tattered condition suggests it may not survive much longer than one more orbit, or about 750 million years, says astronomer Kathryn Johnston of Wesleyan University in Middletown, Connecticut. “We've developed a really compelling picture of a galaxy being torn apart,” she says.

    Another merger is playing out more slowly, but it will pack more punch. The Milky Way is also mixing it up with the nearest nondwarf galaxies: the Large and Small Magellanic Clouds (LMC and SMC), visible as gauzy blurs in the Southern Hemisphere. These companions interact with each other as well as with the Milky Way's extended cocoon of dark matter and hot gas. The combined gravitational tugs produce a tortured-looking system: Gas and some stars form a bridge that connects the two distorted clouds, while the long Magellanic Stream of gas trails behind.

    Some astronomers maintain that the Magellanic Stream consists of gas stripped from the clouds as they slog through the Milky Way's extended shroud of gas. But in 1998, a team of astronomers led by Mary Putman of Australian National University in Canberra also found evidence for a more ethereal stream ahead of the LMC in its orbit. Gas stripping cannot explain that observation, Putman says, because all such material would trail behind the clouds, like hair blown back from a hair dryer. Rather, tidal forces from the Milky Way must draw gas from both the leading and trailing edges of the clouds, just as the moon raises watery tides on both the near and the far sides of Earth. Models of the clouds' orbits suggest that they will spiral into the Milky Way, a swan song that may not play out for another 10 billion years.

    The LMC and its 3.5 billion or so stars are a much bigger mouthful than the Sagittarius dwarf or the other runts sucked up by the Milky Way during the last several billion years. Even at its current distance, the LMC appears to have warped the Milky Way's disk slightly, according to Martin Weinberg of the University of Massachusetts, Amherst. And when the two galaxies merge at last, the union should produce quite a fireworks show when gas-rich clouds collide and collapse from the shocks: enough new star birth in the Milky Way for it to shine at least 25% more brightly for several hundred million years thereafter.

    From galactic death, life?

    But by that time our own galaxy may be road kill, flattened by the onrushing Andromeda galaxy. Doppler-shifted starlight from Andromeda reveals that the two galaxies are closing the 2.5-million- light-year gap between them at nearly 500,000 kilometers per hour. That pace will quicken as the galaxies approach. If the two galaxies are headed straight on, they will smash within 3 billion years, says astrophysicist John Dubinski of the University of Toronto and the Canadian Institute for Theoretical Astrophysics (CITA). The momentum of the galaxies will carry them past each other initially, but the gravitational attraction of their dark matter halos will doom them to coalesce. At twice the size of the Milky Way, Andromeda and its tides will distort our galaxy beyond recognition, says astrophysicist Chris Mihos of Case Western Reserve University in Cleveland, Ohio. “It will be a major car wreck,” he says, “and we're the Yugo in this one.”

    Great “tidal tails” of stars flung into space by the merger will either fall back onto the galaxies or disperse and fade with time. After 1 billion or 2 billion years, Mihos says, the new object will resemble a stirred-up elliptical galaxy, with stars following myriad orbits like moths around a lamp. Direct hits between the widely spaced stars will be extremely unlikely, but colliding gas clouds will make the supergalaxy bright with newborn suns.

    Some researchers have pondered how the encounter will affect our solar system—assuming the sun has not yet swelled into a red giant and fried Earth to a crisp. If the sun is cast into intergalactic space on a tidal tail, it may escape the nascent elliptical galaxy entirely, Dubinski says. In that case, he notes, “we're safe, but our night sky will be devoid of naked-eye stars—sort of like living in downtown Toronto.” Another possible fate might fling the sun inward toward blazing cradles of new stars at the merger's gas-rich core. Massive young stars exploding as supernovae and bombardment by comets nudged from their orbits might make that hotbed too harsh for life to continue. Still, the sky would look spectacular: Even many thousands of light-years from the clusters of newborn stars, says the Carnegie Observatories' Schweizer, “you would be able to read the newspaper at night by the light of the starbursts.”

    Whatever the outlook for our own planet, Schweizer foresees a vibrant future in the supergalaxy born of the merger. The gas in both the Milky Way and Andromeda today is chock-full of the heavy elements needed to build rocky planets, he says, thanks to generations of stars that have processed their nuclear fuel. When the ferment subsides and the most massive stars die off, a vast number of sunlike stars and planetary systems will age in unison for billions of years. “Huge waves of civilizations may reach maturity nearly simultaneously,” Schweizer speculates. If so, today's elliptical galaxies—the remnants of long-ago mergers—may teem with life born in the shards of the mighty collisions that continually reshape our universe.

  15. New Probe to Chart the Milky Way

    1. Alexander Hellemans
    1. Alexander Hellemans writes from Naples, Italy.

    The oldest branch of astronomy is about to get a new boost. Called astrometry, it began in the 2nd century, when Greek astronomer Hipparchus of Nicea measured the brightness and positions of more than 1000 stars in the celestial sphere. Now an upcoming NASA mission promises to pinpoint millions of stars and uncover perhaps thousands of planetary systems in the Milky Way.

    Astrometry took a back seat to astrophysics and cosmology for decades, until the European Space Agency (ESA) launched a satellite in 1989 named Hipparcos. By the time it had completed its mission in 1993, Hipparcos had determined the positions of over 1 million stars, 120,000 of them with an accuracy 10 times better than can be achieved from the ground, providing a fine-scaled map of our galactic neighborhood out to 500 light-years. Hipparcos scientists were also able to determine precise distances to many stars from their parallax—the ellipse a star appears to describe on the background of more distant stars as Earth circles the sun. “Hipparcos opened the eyes of many astronomers,” says Lennart Lindegren of Lund University in Sweden.

    Now NASA is hoping to grab some of this limelight with its Full-Sky Astrometric Mapping Explorer (FAME), a $162 million satellite set for launch in 2004. The brainchild of astronomers at the U.S. Naval Observatory in Washington, D.C., and the Harvard- Smithsonian Center for Astrophysics, FAME will feature a telescope with mirrors that allow it to observe stars in two different parts of the sky at one time, increasing the data flow. Thanks to FAME's bigger telescope and better charge-coupled devices, it will peer 10 times deeper into space than Hipparcos—covering about 1000 times more volume—and chart a whopping 40 million stars.

    Over its 5-year lifetime, FAME will observe every star 1000 times, enough repetition to plot stellar positions to within 50 millionths of an arc second—the apparent size of a house on the moon, as seen from Earth—and determine precise parallaxes. Among the 40 million twinkles FAME plans to keep an eye on are a number of Cepheids, variable stars that wax and wane in brightness. Because the interval between pulses is directly related to a Cepheid's absolute brightness, these beacons are used as yardsticks for measuring distances from Earth to other galaxies. By precisely determining the parallaxes (thus distances) of about 40 nearby Cepheids, FAME will allow scientists to reduce the uncertainty in this cosmic scale bar from as much as 20% down to about 1%.

    Sifting the data for unpredicted wobbles in star movements should turn up a bounty of other prizes, from unknown binary systems to an estimated 25,000 extrasolar planets that FAME scientists say might be hiding among these millions of stars. Observing the speeds at which stars whip around the galactic center should also help scientists better calculate the total mass of the galaxy and refine its proportion of dark matter, which is believed to make up about 90% of the total mass. “I think [FAME] will be a same leap forward as the one we had with Hipparcos,” says George Gatewood of the University of Pittsburgh, who will use the satellite to hunt for extrasolar planets.

    Nor will FAME have the last word: NASA aims to track stars with even greater precision with its Space Interferometry Mission, a satellite it hopes to launch in 2006. And ESA is considering plans for the most ambitious mission of all, the Global Astrometric Interferometer for Astrophysics. A possible go after 2008, this satellite would chart nearly the whole Milky Way. The renaissance of astrometry will continue.

  16. Into the Lair of the Beast

    1. Erik Stokstad

    After charting swift stars in the heart of our galaxy, scientists are convinced that a supermassive black hole is pulling the strings. Now they are striving to glimpse the monster's shadowy point of no return

    VINCENT: Captain, the ship has been programmed. I don't have the information to override.

    PIZER: You mean we're going into the black hole?

    HOLLAND: Yup.

    Aside from the crew who went down with their ship millions of light-years from Earth in Disney's 1979 cult classic The Black Hole, nobody has peered into the maw of one of the most awesome forces in the universe. Such terrors, it turns out, lie in wait much closer to home than Hollywood could have ever imagined. Just 26,000 light-years from Earth, in the center of our own galaxy, broods a behemoth that would snack as readily on stars as on spaceships. In the last 2 years, scientists have firmed up evidence for this supersized black hole, which has swallowed enough gas and dust to equal the mass of more than 2 million suns.

    The quest to pierce the dusty veil that shrouds the heart of the Milky Way—and track down the black hole there—has taken more than a decade. It has pushed telescope technology to its limits. But astronomers have glimpsed stars whirling around our galaxy's inner sanctum at speeds up to 1500 kilometers a second, 50 times faster than Earth circles the sun. Only the relentless grip of a supermassive black hole could keep these frenzied stars locked into orbit within the galactic center.

    With the beast's identity now known, astronomers hope next to better understand its feeding habits. “We have a unique laboratory in our galaxy,” says Andrea Ghez of the University of California, Los Angeles (UCLA). “It's the only place to see a supermassive black hole influencing its neighborhood.” Smaller black holes, about the mass of our sun, dot our galaxy by the millions, and observations of stars and gas dashing around the centers of distant galaxies have betrayed other supermassive black holes. But none is as accessible as our superheavyweight, whose combination of mass and proximity to us gives astronomers a chance to study the workings of a black hole like they can no other. Scientists are also raising the tantalizing prospect of viewing, for the first time, an event horizon—the eldritch boundary beyond which nothing can escape a black hole's gravity. Spotting this point of no return would be “the first direct, conclusive evidence” for an effect of extremely strong gravity as predicted by general relativity, says Fulvio Melia, an astronomer at the University of Arizona in Tucson. “That would be extremely exciting.”

    Star search

    The notion that a supermassive black hole squats in the galactic center, an area spanning 30 light-years, was first proposed by Martin Rees and Donald Lynden-Bell in 1971. Seeking to explain the tremendous energy—equal to 100 million suns—pouring from the center, the two astronomers suggested that vast amounts of turbulent gas and dust were reaching fierce temperatures during their plunge into a black hole. That idea has fallen by the wayside. Much of the heat, it turns out, comes from the millions of stars packed into the galactic center.

    By the early 1980s, however, a new line of evidence for a titanic black hole had emerged: observations of a powerful radio beacon at the galactic center, called Sagittarius A* (Sgr A*). The radio waves, astronomers speculated, are shed by electrons energized by a black hole's gravity. However, other phenomena, such as matter falling onto clusters of neutron stars, can also emit powerful radio waves. “Everyone has expected for 20 years that our galaxy would have a [supermassive] black hole,” says Rees, who is with the University of Cambridge in the United Kingdom. “But the evidence was depressingly slim.”

    A stronger argument emerged from investigations of the galactic center in the 1980s. A team led by Charles Townes of the University of California, Berkeley, used infrared telescopes to track the movements of gigantic gas clouds, spanning up to trillions of kilometers, in the innermost 3 light-years of the galactic center. Because clouds nearest the center seemed to move faster than ones farther out, the team suggested the clouds were all being tugged by a massive black hole as heavy as 3 million or 4 million times the mass of the sun. “We thought we had clinched the case,” recalls Reinhard Genzel, who is now at the Max Planck Institute for Extraterrestrial Physics in Garching, Germany. “But the community at the time didn't believe us.” Other scientists suggested that it was possible the gas clouds were being distorted by internal magnetic fields or buffeted by stellar winds.

    A more reliable way to hunt for large dollops of hidden mass is to track individual stars. Unlike wispy clouds, stars don't veer from their orbits unless pulled by strong gravity. But it's hard to see pinpricks of starlight deep inside the nimbus of stars and light-blocking dust that cocoons the galactic center. What does escape this shroud is electromagnetic radiation at longer wavelengths, such as infrared and radio, that undulates through the dust.

    By 1990, infrared detectors had advanced to the point that they might be sensitive enough to make out emissions from stars inside the galactic center. Genzel's team attached just such a detector to the European Southern Observatory's 3-meter New Technology Telescope in La Silla, Chile. The stars they could discern were awfully fuzzy, partly because the few infrared rays that made it out of the cloud and all the way to Earth were getting knocked around by our own atmosphere. To reduce this distortion, Genzel and his colleague Andreas Eckart, now at the University of Köln in Germany, used a trick called speckle imaging, in which they took many short exposures—like a sports photographer snapping photos of a twirling ice skater. A computer compared the pictures and extracted a true image from the shimmer. But the data were so heavily processed, says Genzel, that when the team members insisted they could make out the motion of stars, “people weren't inclined to believe us.”

    They kept at it, and by 1996, they had seen enough stellar motions to piece together the orbits of 39 stars. (To view an animation, see Meanwhile, a group led by UCLA's Ghez had started to make similar measurements with the higher resolution 10-meter Keck telescope on Mauna Kea, Hawaii. At a 1996 conference in La Serena, Chile, the teams compared notes and found they were witnessing similar darts and dashes. “That's when we began to believe these changes were real,” says Genzel.

    He and his colleagues calculated that the puppet master must have a mass about 2.45 million times that of our sun. The finding was quickly backed up by Ghez's team, which is now taking even finer snapshots of the galactic center using newly installed adaptive optics—a system of pistons that fine-tune the shape of a mirror to cancel out atmospheric turbulence (Science, 19 November, p. 1504). The crucial point is that all this mass—recent estimates put Sgr A* at up to 2.6 million solar masses—must fit inside the orbits of the rapidly moving stars, a gap about 16 light-days across. That implies a density so high that only a black hole could explain it. “This is a very important and very beautiful result,” says Rees. “It rules out anything we can plausibly propose except for a black hole,” adds Leo Blitz of the University of California, Berkeley.


    As supermassive black holes go, ours is puny. Other galaxies house the true heavyweights, such as the 3-billion-solar-mass black hole in M87, a galaxy 50 million light-years away. But the behavior of Sgr A* is peculiar. When most black holes at galactic centers suck in matter, they pump out streams of radio waves, x-rays, and gamma rays. Sgr A* is surrounded by an ample supply of gas, yet the only certain signal detected from this region has been radio waves. The leading explanation is that Sgr A* gulps its food without chewing it up much.

    The idea—generally called advection dominated accretion flow—is that infalling gas heats up but radiates inefficiently. Instead, the particles grow stupendously hot as they plummet faster and faster toward the black hole. Some heat escapes as infrared radiation, while the accelerating electrons emit radio waves; however, most energy disappears with the particles when they cross the event horizon. “It's an elegant solution,” says Andrew Fabian, an astronomer at the University of Cambridge.

    Exactly how this disappearing trick works is still being debated. One idea, proposed by Arizona's Melia, is that the magnetic fields spun by the infalling gas are weak. If so, this would lead to inefficient synchrotron radiation, the way in which electrons give off energy when they are accelerated by a magnetic field. That could explain why the observed radio emissions are many hundreds of times weaker than predicted. Alternatively, Rees proposed in 1982 that the ionized gas near Sgr A* might come in two temperatures, its protons warmer than its electrons. The radio emission that does escape from Sgr A* might come from these cooler electrons. But the protons, being poor radiators, silently carry the bulk of the infalling matter's energy with them to the grave—a scenario since refined by theorists such as Ramesh Narayan of the Harvard-Smithsonian Center for Astrophysics in Cambridge, Massachusetts.

    The latest models suggest that much of the black hole's prey may elude it. In a paper published last February in the Monthly Notices of the Royal Astronomical Society, Roger Blandford of the California Institute of Technology in Pasadena and Mitchell Begelman of the University of Colorado, Boulder, propose that most of the hot matter spurts out as high-speed winds. Propelled by heat or magnetic fields, these gusts would tend to blow gas away from the black hole. The winds themselves would radiate a bit, but this would also reduce the amount of matter sucked in. The nature of this outflow is unclear. The winds might stir the gas and keep it circulating, like roiling water. Or they may blast the gas away in a tightly focused jet, similar to a model developed by Heino Falcke of the Max Planck Institute for Radio Astronomy in Bonn, Germany.

    So far, radio astronomers haven't been able to vet these detailed ideas about black hole feeding. But data from new x-ray telescopes may help. NASA's Chandra X-ray Observatory, launched last July, will be able to spot objects in the galactic center that are 10 times fainter than those any previous x-ray satellite could spot. Chandra may also be able to spot high-energy radiation cast off by matter falling into our homegrown black hole. And if it turns out that Sgr A* is swallowing matter without churning out radiation, other black holes hidden in distant galaxies may be doing the same thing. The visible universe could be losing far more matter than scientists had estimated—and those elusive black holes might not be bulking up as slowly as they seem to be.

    Shadow world

    Perhaps the ultimate observation of our galaxy's black hole would be a glimpse of its boundary—the point of no return. According to Falcke, the event horizon should be visible as a shadow outlined by radio waves. Falcke, Melia, and Eric Agol of The Johns Hopkins University in Baltimore, Maryland, estimate that this gloom should extend up to five times the width of the event horizon itself, as any radiation skirting the black hole would be pulled out of our line of sight. If astronomers spotted an event horizon, they would have direct evidence for a bizarre phenomenon predicted only by general relativity. The horizon's shape may also reveal whether the black hole is spinning, which ought to twist the fabric of space-time.

    But it may be a few years before that sort of view is possible, says Falcke. About 300 light-years away from the galactic center is a mysterious swath of ionized gas that blocks our vision by scattering radio waves. Trying to tune in radio emissions from Sgr A* is “like looking through frosted glass,” says Geoff Bower of the National Radio Astronomy Observatory in Socorro, New Mexico. “The only thing we see is a smeared-out blob.” The scattering decreases with shorter wavelengths; astronomers accustomed to 7-millimeter radio waves are now pushing to resolve 1- to 3-mm wavelengths. That's a tough job, because existing antennas perform poorly at shorter wavelengths, a problem exacerbated by atmospheric turbulence. If these issues can be solved, Falcke says, the event horizon may come into focus at about 0.85 mm.

    Reaching that target will allow scientists to see “all the way down to the bottom of the falling gas,” says Melia. That will be just as thrilling as riding a spaceship into a black hole—and unlike the fate of the Disney vessel, this voyage would be only the beginning.

  17. Biography of a Recluse

    1. Erik Stokstad

    If the everyday life of our galaxy's central black hole is cloaked in mystery, its past is even murkier. Where did Sagittarius A* come from? The most plausible model, says theorist Scott Tremaine of Princeton University, is that a huge gas cloud near the center of the young Milky Way collapsed under its own gravity, spawning a black hole. No birth record exists, however: The black hole could be almost as old as the universe, some 15 billion years, or it may be much younger.

    As a toddler, the black hole would have weighed no more than a few hundred thousand solar masses. Throughout its life it has probably been grazing quietly on wisps of gas, gradually swelling to more than 2 million solar masses. Punctuating this routine every 10,000 years or so, models suggest, are weeks-long gorges in which Sagittarius A* may sink its gravitational fangs into a star that drifts too close and rip it to shreds. During such a meal, the black hole might belch enough radiation to flare as bright as a supernova, briefly outshining all the stars in the Milky Way. Although much of this outburst would be sopped up by dust in the galactic center, today's infrared, radio, and x-ray telescopes would be able to discern such a flash.

    Our own solar system, however, is safe from being munched. Like other supermassive black holes, Sagittarius A* cannot engulf the bulk of its galaxy: It lacks the gravitational brawn to influence matter much more than a few tens of millions of kilometers beyond its boundary. “There is no great sucking going on,” notes Julian Krolik of The Johns Hopkins University in Baltimore. Matter that orbits a black hole must lose angular momentum to approach, just as a satellite has to be slowed by atmospheric drag before it falls to Earth. Our solar system has far too much momentum to get pulled toward the galactic center, says Tremaine.

    Instead, Sagittarius A* has a date with another hulking black hole. In a few billion years or so, the Milky Way is likely to crash into the Andromeda galaxy (see p. 62), which harbors a supermassive black hole perhaps 50 times bigger than our own. The two black holes will spiral together in a violent tango, releasing surges of gravity waves, and ultimately merge. The galactic smashup will refuel the titanic black hole and also trigger new star formation, dramatically brightening Andromeda-Milky Way for a few hundred million years.

    Eventually, the gravy train will end. Little nourishment will remain for the black hole, as matter—in our galaxy and throughout the universe—gets locked up, out of reach, in dead stars. The galaxy “will get darker and darker and less and less interesting,” says Tremaine. Hundreds of trillions of years from now, when the last lights in the Milky Way have winked out, all that will remain will be a graveyard of stellar corpses—and a silent, hungry black hole.

  18. A Magnifying Glass for the Milky Way

    1. Govert Schilling*
    1. Govert Schilling is an astronomy writer in Utrecht, the Netherlands.

    By watching stars for rare flickers, astronomers hoped to glean clues to the nature of dark matter; instead, they have gained a richer knowledge of other beasts in our galactic menagerie

    About a decade ago, Bohdan Paczynski of Princeton University hit upon an ingenious approach to probing one of astronomy's biggest mysteries: the nature of the dark matter, invisible to telescopes, whose gravity keeps our own Milky Way from flying apart as it spins. His idea was to mount a search for dark matter based on the principle that a massive object's gravity can act as a lens, bending light from other stars. If large chunks of dark matter—planets or the failed stars called brown dwarfs—are floating in the galaxy's spherical halo, every so often one of them should float across our line of sight to a background star. Its gravity should briefly boost the star's brightness, a phenomenon called microlensing. In the early 1990s, Paczynski and others set out to catch the dark matter by monitoring millions of stars at once for the telltale flickers.

    Ten years later, Paczynski and his colleagues remain stumped by the riddle of dark matter. But far from being a bust, microlensing has opened a new window on the Milky Way, including possible discoveries of extrasolar planets and insights into curious variable stars. Observations of the rare lensing events have also forced astronomers to ponder a new structure for our galaxy: that rather than being a perfect pinwheel, it seems to have a bar-shaped clot of stars at its center. The study of microlenses, says Roger Ferlet of the Institut d'Astrophysique de Paris in France, has become “a completely new way of doing astronomy.”

    It's a search for needles in a cosmic haystack: At any moment, only about one in a million stars is expected to have its rays sharpened in our line of sight by an object closer to Earth. So the astronomers monitor stars en masse—millions of them, in the Milky Way's central halo as well as in two companion galaxies, the Large and Small Magellanic Clouds, that cling to our galaxy. Four teams have pursued the search. First off the blocks was the French collaboration Expérience de Recherche d'Objets Sombres (EROS); hot on its heels were the Optical Gravitational Lensing Experiment (OGLE), run by Paczynski and colleagues at the University of Warsaw in Poland, the U.S.-Australian Massive Compact Halo Objects (MACHO) project, and a smaller French effort called Disk Unseen Objects (DUO). All four have relied on ground-based telescopes, equipped with charge-coupled device detectors, plus computers to sift through stacks upon stacks of brightness measurements. “It was the very first time that astronomers handled such huge amounts of data,” says Ferlet, an EROS team member.

    The telltale flickers last anywhere from a few hours to a couple of months; generally, the longer the duration, the heavier the object bending the starlight. When the projects first got going, says MACHO team member David Bennett of the University of Notre Dame in Indiana, “objects weighing less than 10% of the mass of the sun were expected to be the most likely lenses” in the Milky Way's halo, where the population of normal stars is sparse. These so-called MACHOs might be brown dwarfs or wandering Jupiter-sized planets.

    After gazing through the halo at the Magellanic Clouds, the teams have caught about 20 instances of microlensing. But most of these events lasted for weeks—long enough that they are best explained by objects tipping the scales at about half the mass of our sun. Nor are they nearly abundant enough to account for most of the dark matter. These heavy MACHOs might be burned-out stars, called white dwarfs, that have cooled and dimmed; supporting this notion, cool white dwarfs seem to show up in long-exposure photos taken by the Hubble Space Telescope (Science, 10 September, p. 1653).

    Although microlens observations have set limits on the nature of dark matter, the dearth of candidate objects has sent theorists back to the chalkboard to come up with possible new guises for unseen matter in our galaxy (Science, 17 July 1998, p. 332). One is small, solitary black holes. Indeed, the MACHO collaboration did see a long-lasting lensing event toward the galactic center, perhaps caused by a black hole a few times more massive than our sun; Bennett says the searches probably miss more such events, because the data analysis programs are not designed to hunt for lensing that lasts for many months. Other scientists, meanwhile, argue that dark matter could be composed of neutrinos or other elementary particles. That would relegate microlens researchers to the sidelines in the dark matter search, leaving the chase to particle physicists.

    But just as a fruitless search for one's car keys can turn up a $20 bill, lensing observations have revealed some hidden jewels that search teams hadn't set out to find. For instance, the four projects have amassed a trove of data on stars with intrinsic variations in brightness. “One of our early worries was that the detection of zillions of new variable stars would make it hard to distinguish between an actual microlensing event and a peculiar type of variable star,” says Paczynski. “Luckily, that turned out not to be a problem.” It's easy to distinguish the two because a variable star's pulsing appears different at different colors, while a lensed star brightens equally at all colors. And by tracking large numbers of Cepheid variables (a common type of pulsating star) in the Magellanic Clouds, microlensing researchers have worked out how the pulsation period of a Cepheid is influenced by the chemical makeup of its host galaxy. Astronomers assume that a Cepheid's period indicates its intrinsic brightness, which allows them to use these stars as standard candles—beacons whose apparent brightness provides a measure of cosmic distances. The new information will help astronomers correct their Cepheid measurements and thus refine estimates of distances in the cosmos.

    Telescopes that are pointed in a different direction, toward the heart of the Milky Way, have borne witness to another surprise: hundreds of occasions—far more than anticipated—in which lenses appear to be run-of-the-mill dwarf stars. To account for the seeming abundance of these stars, astronomers have suggested that the central bulge of our galaxy, once thought to be spherical, is shaped more like a bar pointing roughly in our direction. That shape would produce more alignments of background stars and lensing objects than expected. But the data don't yet prove that the Milky Way is a barred spiral. Further lensing observations, says Bennett, “are going to be pretty important in determining the structure of our galaxy.”

    Perhaps the most thrilling payoffs of the microlensing searches are the apparent discoveries of extrasolar planets. When a lensing star has a companion planet, its light should flicker, either dimming or brightening, if the planet's orbit crosses the line of sight, an effect more pronounced than dimming due to a planet's transit across the face of a star. Measurements of these spikes can yield a rough estimate of a planet's mass and its orbital radius. So far, two serious exoplanet candidates have been found, says Bennett, who leads a project, called the Microlensing Planet Search (MPS), that follows up on alerts from the microlensing programs. Along with collaborators in Japan and New Zealand, MPS in 1998 spotted what appears to be the first low-mass exoplanet orbiting in a parent star's “habitable zone,” in which liquid water could exist (Science, 1 October, p. 70), says Philip Yock of the University of Auckland in New Zealand.

    More controversial is the second candidate, which the MPS team described in Nature last November. Bennett's group claims to have found for the first time a planet that orbits two stars (Science, 20 August, p. 1191). But according to a competing team called Probing Lensing Anomalies Network (PLANET), the variations in starlight observed during the microlensing event could be attributed solely to the binary's complex pas de deux.

    Despite their skepticism about the binary find, PLANET members say that microlensing, more than any other search technique, has enabled astronomers to set limits on the abundance of exoplanets. After observing about 100 microlensing events, PLANET has concluded that the fraction of stars orbited by Jupiter-mass planets in the inner regions of their solar systems cannot be higher than about one-third.

    Microlensing's power to peer deep into our galaxy may be nonpareil, but soon only one team will carry the banner for the technique. After using up their allotted funding, DUO is done and MACHO stopped gathering data last month, while EROS is slated for shutdown in 2002. That will leave the field wide open to OGLE, which later this year will be upgraded with a larger camera that's expected to produce an unprecedented 5 terabytes of data per year. The deluge should double the number of cataloged lensing events.

    Until astronomers put into orbit a telescope dedicated to microlensing, there should be plenty yet to discover from Earth. “The possibilities of ground-based observations have not yet been fully explored,” says Paczynski, who would love to see a continuous, all-sky lensing patrol. “We can still get a tremendous improvement by increasing the number of stars in our surveys.” The dark matter may still be at large, but the bright matter of our galaxy is coming into ever-sharper focus.

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