# News this Week

Science  07 Dec 2007:
Vol. 318, Issue 5856, pp. 1534
1. MATHEMATICS EDUCATION

# U.S. Expert Panel Sees Algebra As Key to Improvements in Math

1. Jeffrey Mervis

BALTIMORE, MARYLAND—No single report will end the decade-long debate about why U.S. students aren't doing better in math. But last week, a panel of experts assembled by the Department of Education signaled it had reached consensus on one of the most important topics in that debate: how students can become proficient in algebra.

Usually offered in the 8th or 9th grade, algebra is a gateway course for high school mathematics; without mastering algebra, a college degree in science or engineering is impossible. Its importance has made it the primary focus of the National Mathematics Advisory Panel, convened in April 2006. Last week, the group of 19 mathematicians, psychologists, and educators vetted a 68-page draft report due out this winter that members hope will play a major role in shaping math instruction across an education system that comes in 50 state flavors, with variations by 14,000 local school districts.

The report, debated line by line during an open 6-hour meeting at an airport hotel here, contains dozens of recommendations on how to boost student achievement in math. Taking aim at watered-down courses, the report defines the content of a rigorous algebra course as well as what students need to know before taking it. It urges school districts “to avoid an approach that continually revisits topics, year after year, without closure,” part of what critics deride as a “mile-wide, inch-deep” math curriculum. It recommends giving teachers more authority to choose those educational materials and practices best suited to their students. It also calls for more useful assessments of what students know and for shifting educational policy debates “away from polarizing controversies.”

At the same time, says panel chair Larry Faulkner, a chemist and former University of Texas president, the report will note that little or no good data exist on several hot-button issues. On choosing between a prescribed math curriculum presented by the teacher and one that incorporates what piques the interest of students, Faulkner notes, “it's a matter of religion, and it's important for the world to know that.” That uncertainty is also true, he says, for whether elementary school students should be taught by math specialists rather than their regular classroom teacher. On the use of calculators in class, the group was deliberately equivocal: Math educator Douglas Clements of the University at Buffalo, State University of New York, told his fellow panelists that “we found limited to no impact on computational skills, problem-solving abilities, and conceptual development.”

Despite the panel's desire for a consensus document, many issues seem likely to remain contentious long after the report is released. Take the discussion about how to teach arithmetic and whole numbers. Harvard University mathematician Wilfried Schmid argued strongly for including the phrase “the standard” in a paragraph that calls for “fluency with the standard algorithms for addition, subtraction, multiplication, and division.” The two words, especially the article, are a rallying cry for the back-to-basics movement, which cites changes in the mathematics curriculum introduced in the 1990s as a major reason for low test scores. “Without that word,” Schmid exhorted his colleagues, “we are sending a message that anything goes.”

Math educator Deborah Ball of the University of Michigan, Ann Arbor, demurred, arguing that retaining the phrase would hamstring teachers who may want to use student-derived approaches in their lessons. “We're not talking about how to teach math in this paragraph,” she explained, “and the use of alternative algorithms can be a useful tool for teachers. I'd like to drop the ‘the.’” After more discussion, her view was adopted unanimously.

The vote was a cue for Francis “Skip” Fennel, president of the National Council of Teachers of Mathematics and chair of the subgroup that had worked on this section and who supported Ball's position, to take a coffee break. But the discussion wasn't over. As a way to reopen the issue, Schmid said another panel member, Fairfax, Virginia, middle school math teacher Vern Williams, had asked for his reaction to the vote and that “I am not distraught, but I'd be happier if the word were kept.” The panel immediately took a second vote and decided, by a margin of 8-3, with three abstentions, to retain the article. Fennel then walked back in the room and, upon hearing about the new tally, declared: “You mean I lost?”

In addition to embodying the tensions within the math community, the panel is also carrying some heavy political baggage. U.S. Education Secretary Margaret Spellings dropped by the meeting to give the panel a brief pep talk and urge it to finish quickly. Notwithstanding the panel's remaining work—it got through barely half of the 45 paragraphs in its draft executive summary—Spellings was comfortable describing its take-home message later to a small group of reporters.

The report will tell the country “what works” in math education, Spellings explained. “Once we know what works, it's our responsibility to align the resources” from the federal, state, and local governments. Spellings said the report's most important points are the need for students to master fractions, the importance of early childhood education, and the value of developing teacher skills, both during their training and after they are hired. Those messages dovetail with several initiatives proposed by the Bush Administration, including a $250 million Math Now program for middle school students that Congress has so far refused to fund. 2. CLINICAL TRIALS # Gene Transfer an Unlikely Contributor to Patient's Death 1. Jocelyn Kaiser Winding up an investigation into the mysterious death in July of a 36-year-old woman in a gene therapy safety trial, an expert panel this week concluded that the gene transfer was unlikely to have contributed to the tragedy but that this “cannot definitively be ruled out.” Despite “an extraordinary effort,” said chair Howard Federoff of Georgetown University in Washington, D.C., “we still are missing key pieces of information” needed to answer the question asked by the patient's widower: Would she be alive today if she had not taken part in the trial? Just a week before this meeting of the Recombinant DNA Advisory Committee (RAC), the trial's sponsor, Targeted Genetics Corp. in Seattle, Washington, announced that its gene therapy treatment “did not contribute to the patient's death” and noted that the Food and Drug Administration (FDA) had lifted its hold on the trial (Science, 30 November, p. 1363). But issues raised by RAC may linger over the field of gene therapy, which had been blamed for two deaths since 1999. The controversy concerns Jolee Mohr of Taylorville, Illinois, who died on 24 July, 3 weeks after receiving a second experimental gene therapy injection for rheumatoid arthritis in her knee. In September, RAC noted that Mohr apparently died from a fungal infection called histoplasmosis and a large blood clot. Mohr was taking an arthritis drug, Humira, which blocks a proinflammatory cytokine called tumor necrosis factor α (TNF-α) and suppresses the immune system. The protein produced by the gene therapy is also a TNF-α blocker, and if it spread beyond Mohr's knee, the combination with Humira may have left her vulnerable to the fungus. Additional data “do not support [that] theory,” RAC concluded this week. The level of TNF-α blocker detected in Mohr's blood was within the range expected from the dose of Humira she was taking, and it dropped after she received the gene therapy injection on 2 July (see graph). However, RAC recommended that Targeted Genetics develop an assay to distinguish between systemic TNF-α blockers like Humira and the gene therapy product. RAC members also examined the possibility that Mohr had an immune reaction to the gene therapy vector, adeno-associated virus (AAV). Vector DNA appeared in other tissues only at extremely low levels, suggesting that the AAV did not replicate. However, RAC pointed to another possibility: that Mohr's immune system reacted to the virus's protein shell. That could have been tested by measuring certain T cells in Mohr's blood, but no whole blood samples were available. As a result, “an immune response cannot be definitely ruled out,” RAC said. It recommended that all ongoing AAV trials monitor T-cell responses. Even if the vector did play a role, “it was very unlikely to have been a significant contributor” to Mohr's illness and “was not the cause of her death,” which was “primarily” from histoplasmosis with Humira as a risk factor, RAC concluded. FDA official Daniel Takefman said at the RAC meeting that the agency is “in agreement” with RAC's conclusion. Defending the company's announcement that its therapy was not to blame, Targeted Genetics Executive Vice President and Chief Scientific Officer Barrie Carter points out that the data and safety monitoring board for the trial, an independent group, concluded that the death was not related to the trial. That is not inconsistent with RAC's findings, Carter says; the problem is, “you can't prove a negative.” The company now plans to resume the safety trial of 127 patients, but, in keeping with RAC and FDA recommendations, it will not give a second dose to patients if they have a fever, as Mohr did, or show other signs of infection. 3. ACADEMIC FREEDOM # Thai Science Agency Clamps Down on Sensitive Research 1. Richard Stone Concerned about Thailand's image and security, authorities are preparing to restrict foreign research involving three touchy subjects: child labor, prostitution, and a simmering Islamic insurgency. Starting this month, the National Research Council of Thailand (NRCT) will put proposals from foreigners to conduct research in these areas under extra scrutiny before issuing a research permit. The aggressive stance is one facet of revised regulations that require foreign scientists—short-term visitors and residents alike—to obtain research permits. NRCT lists four aims: enhancing cooperation, promoting research that furthers development, controlling natural resources, and “stabilizing the social and economic security of Thailand.” Censorship is not a goal, according to NRCT Secretary General Ahnond Bunyaratvej, who has said his office wants to be a research “facilitator, not an inspector.” NRCT's intention to apply the rules to all foreign-born academics at Thai institutions has touched off a firestorm of criticism. “There is nothing ‘facilitating’ about these regulations. At best, they imply needless, thick layers of red tape. At worst, they are discriminatory harassment of foreign nationals,” fumes one foreigner based at a Thai university who asked to remain anonymous. “Most researchers and university officials here agree that foreign researchers should not be regulated or judged any differently than Thai researchers,” adds Warren Brockelman, a conservation biologist who has been teaching at Mahidol University in Bangkok since 1973. According to the rules, “research involving a foreigner must be conducted jointly with a Thai researcher or consultant.” Applications and reference letters must be submitted at least 90 days before a project is slated to start. Lecturers who do not conduct research need not apply for a permit. NRCT will disseminate the rules at a public meeting next week. In some respects, the regulations codify common sense—and fairness, says Heng Thung, a specialist in satellite data at the Regional Centre for Archaeology and Fine Arts in Bangkok: Scientists who parachute in without knowledge of Thai language or customs should have a local partner. Thung says that many foreign scientists have ignored a long-standing NRCT requirement to deliver a report or thesis after completing a project. Thung also feels that NRCT is justified in taking a stand against foreigners seeking to profit from Thailand's natural resources—developing a drug from a native plant, for instance—without repatriating a portion of the earnings. “Many researchers mine the country,” he says. Thailand also hopes to keep its guard up against questionable research. Earlier this autumn, Korean and Thai newspapers reported that the discredited South Korean stem cell researcher Hwang Woo Suk intends to set up a lab in Thailand. In response, Thailand's science minister, Yongyuth Yuthavong, says he instructed staff members “to be extracareful about collaborations which raise ethical concerns.” NRCT says that it has not received a proposal from Hwang. What troubles some observers is that NRCT is assuming the mantle of moral arbiter. “Sensitive research will be considered project by project,” says Pannee Panyawattanaporn, chief of NRCT's foreign researcher management division. The council will consider factors such as objective, methodology, and the research site, she says. “We want to know whether a project might affect Thailand negatively,” adds another NRCT official, who declined to give his name. The council will consult security officials on sensitive projects, he says. NRCT's policing role could put it in conflict with the local employers of foreign scientists. The council “should reject a project only after consultation with the host institution” and with the institution's assent, says Brockelman. He notes that the grounds for possible rejection are “rather vague.” In a meeting with foreign staff members at Mahidol last week, university officials said that they do not recognize NRCT's right to regulate university staff, according to an attendee. Likewise, Thailand's National Science and Technology Development Agency (NSTDA) “is constructively discussing with NRCT how this measure could be implemented,” says assistant president Sirirurg Songsivilai. “We would ensure that NSTDA's overseas researchers and collaborators are not negatively affected by the regulations.” The regulations could be revised after a period of use, says Pannee. In the meantime, foreign researchers have urged NRCT to consider other approaches to facilitating cooperation, such as seminars and lectures. And the council has some fence-mending to do. “Numerous foreign-born academics have devoted their careers to teaching Thai students and involving them in research. Instead of a thank you, they are suddenly told that all of their research is suspicious,” says the foreign university scientist, who fears that the rules will put a chill on partnerships. 4. BIOTERRORISM # Panel Provides Peer Review of Intelligence Research 1. Yudhijit Bhattacharjee In 2002, U.S. intelligence officials claimed that the Iraqi government owned a number of mobile labs capable of producing biological weapons. After U.S.-led forces invaded Iraq, the labs were revealed to be production facilities for hydrogen used to fill weather balloons. In 2005, a government commission said the error was due to a lack of scientific expertise within the U.S. intelligence community. Now intelligence officials are addressing that problem by opening up their biological research program—most of which is classified—to external peer review. A panel of life scientists from universities, companies, and nongovernmental organizations has begun to assess the merit of projects proposed and conducted by researchers at the 16 agencies under the aegis of the Director of National Intelligence (DNI), as well as grant applications submitted to the agencies. The Biological Sciences Expert Group (BSEG), with 24 core members and an extended network of 40 others, has already met five times this year at DNI's National Counterproliferation Center in McLean, Virginia. In addition to helping screen and design projects to combat bioterrorism, the group will analyze research findings, review the scientific validity of intelligence assessments, and occasionally conduct its own studies. The objective is to raise the review of intelligence research to the standards of other federal science agencies, says Lawrence Kerr, senior bio adviser at the center and a microbiologist formerly at Vanderbilt University in Nashville, Tennessee, who assembled the expert group. He says the research done by intelligence agencies is currently reviewed primarily by the agencies' own scientists and program managers, who have a limited range of expertise. The system “isn't what one would think of as being incredibly robust,” he says. “Such outreach ought to be standard practice, particularly in fields where rapid changes are taking place,” says Dennis Gormley, a senior fellow at the Monterey Institute's Center for Nonproliferation Studies in Washington, D.C., who applauds Kerr for creating the new panel. Kerr says DNI plans to extend the concept to other areas of intelligence research. BSEG's members are being paid annual retainers of as much as$1000, and its core panelists can earn as much as $18,000 a year based on the amount of work they perform. But DNI has not released their names, part of what Kerr says is a necessary veil of secrecy both to protect them from being snooped on by foreign intelligence agents and to avoid jeopardizing their ties to other scientists. Members even keep two sets of notes at meetings, Kerr says, recording “all of their classified stuff on blue paper or pink paper that's kept separate.” Some observers are worried that the secrecy surrounding the panel could cloak work on the development of biological weapons. “Remember, this group is not just advising, it may also conduct research,” says Alan Pearson of the Center for Arms Control and Non-Proliferation in Washington, D.C., adding that there's a history of similar groups in the past “transition[ing] from defensive to offensive work, rationalizing themselves along the way.” Gerald Epstein, a biosecurity expert at the Center for Strategic and International Studies in Washington, D.C., and the only group member to have made his affiliation public, discounts those concerns. He says BSEG provides an extra layer of oversight to the intelligence community's classified programs and can help the United States remain faithful to the Biological Weapons Convention, to which it and 158 other nations are parties. “If members discovered research that was illegitimate, they could take a number of steps to stop it, such as notifying Congress or even going to the press,” he says. Pearson replies that the panel would offer a more credible safeguard “if the broader scientific community knows who they are.” One member of BioChem 20/20, which was formed by the Defense Intelligence Agency in the late 1990s to provide programmatic and strategic advice, thinks that BSEG members will eventually disclose their identities. Geneticist Stephen Johnston of Arizona State University in Tempe says that BioChem members initially chose to remain anonymous. But once satisfied that the work was ethical and noncontroversial, he says, “many of us put the affiliation on our résumés.” 5. NEUROSCIENCE # Gene Variant May Influence How People Learn From Their Mistakes 1. Constance Holden “Once burned, twice shy” works for most people. But some people are slow to learn from bad experiences. Now, a team of neuroscientists in Germany reports on page 1642 that people with a particular gene variant have more difficulty learning via negative reinforcement. The research, which combined brain imaging with a task in which participants chose between symbols on a computer screen, centers on the A1 variant, or allele, of the gene encoding the D2 receptor, a protein on the surface of brain cells activated by the neurotransmitter dopamine. Earlier studies have hinted that this variant alters the brain's reward pathways and thereby makes people more vulnerable to addictions. The new report, from Tilmann Klein of the Max Planck Institute for Human Cognitive and Brain Sciences in Leipzig, Germany, and colleagues, has earned a mixed reception. Among those impressed is geneticist Bert Vogelstein of the Johns Hopkins University School of Medicine in Baltimore, Maryland, who says that “demonstrating that a single-base-pair difference in the genome is associated with a remarkably different ability to learn from past mistakes is quite an accomplishment.” Klein's team enlisted 26 healthy German males, 12 of them with at least one A1 allele. While undergoing functional magnetic resonance imaging (fMRI), the men performed a learning task that involved looking at three pairs of Chinese ideograms and determining which in each pair was the “good” symbol. For one pair, for example, choosing the good symbol elicited a smiley face 80% of the time; the other times the good symbol was chosen, it elicited a frown. For the other two pairs, choosing the good symbol produced positive reinforcement 60% or 70% of the time. The volunteers viewed each pair 140 times during the learning phase, and the researchers at the end saw no significant difference between men with or without A1 alleles in how well they learned to select the good symbols. Then, the researchers presented the subjects with the six symbols in various new pair combinations and evaluated how well each man had learned to identify good symbols versus how well they had learned to steer clear of a “bad” symbol. The ones with the A1 allele did a significantly poorer job of not choosing a bad symbol, suggesting they have a deficit in “avoidance learning.” During the initial learning phase, the fMRI scans of subjects with A1 alleles showed less activity in an area of the frontal cortex and the hippocampus—locales involved in negative feedback monitoring and memory—than did those of the controls. A single A1 allele is associated with as much as a 30% reduction in D2 receptor density and means that “the monitoring system seems to respond less to negative feedback,” says co-author Markus Ullsperger. He suggests that this phenomenon could be related to impaired reward systems in addictions. The D2 story remains tangled, however. “Everyone realizes [the D2 receptor] is critical for reward and many other behaviors,” says David Goldman of the National Institute on Alcohol Abuse and Alcoholism in Bethesda, Maryland. But, he says, the A1 allele has not been shown to alter how the receptor operates. Geneticist Neil Risch of the University of California, San Francisco, adds that this allele “has been a candidate gene for every imaginable psychiatric phenotype for 18 years now, and to my knowledge none of the originally reported associations has held up.” Nonetheless, cognitive neuroscientist Michael Frank of the University of Arizona in Tucson says the study shows that differences in responses to negative feedback can be “reliably predicted by genetic factors controlling dopamine D2 receptor density” and that this connection is backed up by relevant patterns of brain activation. 6. ARCHAEOLOGY # The Vanishing Fremont 1. Keith Kloor* 1. Keith Kloor is a senior editor at Audubon magazine. What forced the Fremont Indians into sky-high cliff dwellings 1000 years ago, and why did they disappear a few hundred years later? A rugged Utah canyon yields new clues When Larry coats pulled himself up to an overhang near the top of a pinnacle in Range Creek Canyon, more than 200 meters above the valley floor, his left foot landed on a perfect square that had been pecked into the rock face, exactly where a climber would want it. He looked up and a mysterious, hidden world from Utah's prehistoric past revealed itself. An obscure buttress held pictographs only visible from this precarious spot. Climbing even higher, he followed a series of steps carved into the sandstone wall that led to the multipinnacled summit. From there, Coats, a paleoecologist at the University of Utah in Salt Lake City and a professional climber, rappelled down the rock face to explore lower ledges and overhangs that were accessible only from the summit. He found 1000-year-old granaries—food storage caches made of mud, stone, and wooden poles—built into the cliff wall, as well as pottery remnants, more rock art, the outlines of subterranean pit-house structures, and a metate, a stone used to grind corn. The metate “was perfectly placed, tucked carefully under a ledge, as though someone was intending to come right back and get to work grinding maize,” recalls Coats, who has surveyed the cliff ‘s pinnacles over the past two summers with archaeologists. The sky-high lodgings and accouterments that Coats found are part of a much larger constellation of sites currently being documented in this remote canyon nestled behind the towering Book Cliffs, 240 km southeast of Salt Lake City. Range Creek's reclusive owner sold it to the state of Utah in 2001, and archaeologists have been amazed by its spectacularly preserved ruins. Newly dated to roughly 1050 C.E., Range Creek was one of the more populous settlements of the Fremont people, enigmatic farmer-foragers who lived mostly in what is present-day Utah and western Colorado. After years of surveying, researchers have begun to work the giant site in earnest. They made their first round of excavations last summer and are working to build a tree-ring record and gather radiocarbon dates, says archaeologist Duncan Metcalfe, who heads the Range Creek Research Project at the University of Utah, Salt Lake City. The scientists hope that the site's archaeological riches, including an apparent network of caved-in pit-house villages just above the valley floor, will yield insight into what is perhaps the greatest mystery concerning the Fremont: Why did they vanish? Metcalfe and others believe that the conditions that led to the Fremont's puzzling disappearance in 1300 C.E. are vividly expressed in Range Creek's social disintegration roughly 150 years earlier. “Range Creek is like finding a new library vault full of information,” says Kevin Jones, Utah's state archaeologist and a member of the Range Creek research team. “Those books are going to be extraordinarily telling and valuable.” Indeed, Metcalfe and others believe that Range Creek's secrets may ultimately reveal information beyond the Fremont culture itself. The Fremont's sudden collapse 700 years ago parallels that of other long-standing Southwestern cultures, including the Anasazi, the Fremont's cliff-dwelling neighbors in the Four Corners region. Experts consider the Southwest in the 1200s to have been extremely tumultuous but are split over which was the greater destabilizing force: a downturn in the environment that made farming untenable or a fracture in the social order. Whatever the trigger, fear and violence seem to have spread like wildfire throughout the region in the 13th century. At Mesa Verde in Colorado, for example, the Anasazi sought shelter high in the cliffs and left abundant evidence of gruesome violence and cannibalism (Science, 8 September 2000, p. 1663). The social upheaval extends south, reaching into places like present-day Phoenix, where the Hohokam and other prehistoric peoples also massed together in self-defense in the 13th century. “By 1275, everybody in the Southwest is living in a fort,” says archaeologist Steven LeBlanc of Harvard's Peabody Museum of Archaeology and Ethnology, whose numerous works assert that the Southwest at the time was beset by warfare. Range Creek, where the Fremont uncharacteristically clustered in fortresslike hide-aways and stashed their food in hidden caches, suggests similar strife some 100 or 150 years earlier. Located at the extreme northern fringe of the Southwest, Range Creek was always marginal for farming, notes Metcalfe. Climate changes and subsequent new survival strategies may have occurred there “in advance of what's happening later throughout the Southwest,” he says. ## Farmers, foragers, or both? In the late 1920s, young archaeologist Noel Morss was exploring central Utah's rugged canyon country when he found gray pottery, moccasins constructed from deer hocks, and visually arresting trapezoidal figures, which were displayed on clay figurines and pictograph and petroglyph panels along the banks of the Fremont river. These material traits had previously been considered an offshoot of an earlier farming culture that flourished south of the Colorado River from 750 C.E. to 1300 C.E. and is known today as the Anasazi or Ancestral Puebloans. But Morss felt the artifacts showed an originality that set them apart from the Anasazi, who wore sandals, lived in elaborate cliff dwellings, and drew Kokopelli and stick figures. He concluded that the “Fremont drainage proved to be the seat of a distinctive culture.” His general characterization of the Fremont has held up remarkably well, and the name stuck. Ensuing excavations of Fremont sites throughout Utah have uncovered a hodgepodge of hunting, farming, and foraging habits, however, and today the Fremont are rather fuzzily defined. One camp maintains that they were country cousins of the Anasazi, primarily farmers living in pit houses. Another camp has contended that they developed in situ from a preestablished archaic culture and were predominantly hunter-gatherers who incorporated farming into their repertoire. “We still don't know who they were, much less what happened to them,” says Fremont expert Jerry Spangler, executive director of the Colorado Plateau Archaeological Alliance, a Utah-based antiquities preservation group. He and some others define the Fremont as “farmer-foragers” who switched between hunting and gathering and farming, depending on circumstances. That versatility makes their collapse even more of a mystery. “They could do it all,” says Spangler. “That's what makes them so unique among southwestern cultures.” Range Creek turns out to be an ideal laboratory for discovering more about the Fremont. The rugged landscape, which today remains sparsely inhabited and virtually roadless, has helped keep both the archaeology and the ecosystem largely intact for the past 1000 years. That makes the site a rare prize for southwestern archaeologists, who often work only one step ahead of developers breaking ground for roads and houses. “This is the first time in my life I won't have a bulldozer at my back,” says Metcalfe. Range Creek's protection should continue, because the University of Utah has recently secured a 20-year lease on a 486-hectare parcel containing the greatest concentration of Fremont ruins. Metcalfe runs a summer field school there as well as a multidisciplinary platoon of scientists, with grants totaling roughly$300,000 per year from the state of Utah and the National Science Foundation.

But the work is slow: Metcalfe's team has surveyed just 10% of the 20,234-hectare canyon and expects the total number of sites to number in the thousands. And although researchers have spotted five sets of human remains eroding out naturally, Metcalfe says he has no plans to disturb them, much less do DNA testing. Because Range Creek is largely public land, soon after archaeologists discovered the bodies they notified neighboring Indian tribes as required by law. Tribes typically prefer human remains to stay in their original place of burial. To prevent any conflict, researchers find it easier to avoid the bones altogether.

Instead, Metcalfe and others focus on the granaries and pit houses. Together, these artifacts suggest a society under stress, competing for dwindling food sources, and splintering into self-protective encampments. Of the nearly 400 sites documented in the canyon thus far, 80 are granaries placed far up cliffs and concealed on narrow ledges or under overhangs. The dense concentration of these storage chambers and their hidden nature is “unprecedented” in Fremont history, says Spangler. Range Creek's granaries “are the most inaccessible I've ever seen,” agrees Coats, even harder to reach than those of the Anasazi, which were also generally made of mud and stone and perched on cliff ledges. The inaccessible food caches suggest that the Fremont were defending their food supply. Jones speculates that the Fremont were “scatter hoarding,” spreading their food out in multiple hiding places: “You risk losing some of it, but at least if another person gets into it, they've only got one bit.”

Last summer, Coats found additional compelling evidence of defensive settlements. For example, above a pit-house site researchers had dubbed the “deluxe apartment in the sky” because it is nearly 300 meters above the valley floor, Coats found piles of boulders strategically placed at the access points of the ridge. There's even a log still wedged underneath one of the big rocks. “I assume a lever was in place at one time, where they could release the rocks down onto anyone who was approaching,” says Coats. “It certainly looks like a defensive weapon.”

Another site—atop a butte and “exposed to all the weather,” says Coats—is nicknamed “the fortress” because it contains similar walls of boulders perched at the edges of the ridge. Here Coats observed numerous artifacts on the ground by four well-used pit houses, including metates, pottery fragments, and lithic flakes. All this “indicates quite a lot of activity on top for a significant amount of time,” he says, and suggests long-term, rather than seasonal, occupation. Researchers have discovered numerous other dwellings wedged on the tops of steep ridges, although the Fremont's cornfields were apparently far below in the floodplain. These houses “are not next to their farm fields, and they are places where grandma and grandpa would have a hard time getting to, and where your children, with one misstep, would fall and get hurt or die,” says Jones. “Why would you live in a place like that?”

For defense and safety, researchers hypothesize—but defense against whom? Until recently, Jones and other Range Creek researchers thought that the cliff-top dwellings represented the terminal stage of the Fremont, in the 1200s or 1300s, the same time that the Anasazi retreated into cliff dwellings at Mesa Verde. Jones had expected that the lower sites just above the valley floor, where huge circular stone alignments suggest pit-house villages, were earlier, perhaps 900 C.E. to 1100 C.E.

But the new data reveal that the Fremont on the ridge tops and in the villages may have co-existed, perhaps about 1050 C.E. A dozen radiocarbon dates, obtained from corn, arrow shafts, granary beams, pit-house rafters, and other organic material have produced a tantalizing pattern, says Metcalfe. Of the 12 dates, 10 share a 95% confidence interval that falls between 970 C.E. and 1130 C.E., with the average falling at 1050 C.E. To further narrow the range, Metcalfe plans to use tree rings, which offer accurate dating to the year.

Based on the density of pit-house alignments in the valley, Metcalfe estimates that a total of about 1000 Fremont lived in the canyon. But there are no trash middens, as expected if the Fremont had a long-term presence there, he says. “They stayed for a relatively short time and got out fast,” he believes.

The defensive settlements and 1050 C.E. date are commensurate with sites in nearby canyons along the Green River, including Nine Mile, a spectacular rock-art site that also features remote granaries and fortresslike structures atop ridge tops. “Everything we have in Nine Mile and Range Creek points to groups of people protecting themselves and their food,” says Spangler. In addition to the shields and human combat depicted in Nine Mile's rock art panels, researchers in 1992 found a child buried with an arrow point in its chest cavity.

The Fremont also apparently massed together later, during the 1200s, on a scale much larger than Range Creek at a site called Five Finger Ridge in south-central Utah. The giant site is radiocarbon dated to between 1200 C.E. and 1300 C.E., near the end of the Fremont period, and includes remote granaries tucked high in the cliffs and more than 60 structures, including pit houses, packed tightly together on a knoll.

At Range Creek, if the dates for valley dwellings do indeed coincide with those in the ridges, it's unlikely that the Fremont were protecting themselves from outsiders: The whole region was settled by Fremont, says archaeologist Joel Boomgarden, a member of the research team. “I'd be willing to bet it's from people within the canyon. They're probably defending themselves against their neighbors.”

## The dry years

But why? Was it social or climatic factors, or some combination of the two, that splintered Fremont society? New climatic records offer clues. In several studies published this year, paleoclimatologist Larry Benson of the U.S. Geological Survey (USGS) in Boulder, Colorado, plotted out a series of major droughts that pummeled the Midwest and Western regions from the early 11th century to the end of the 13th century. He borrowed a drought index—which uses prehistoric tree-ring data on precipitation and temperature to estimate soil moisture—from Edward Cook of Columbia University and his colleagues. The index charts conditions year by year, which Benson and colleagues then compared to events in some of the agrarian cultures that melted away during this span, such as the Anasazi, Fremont, and Cahokia; the latter farmed the Mississippi River floodplains and valleys.

If the Range Creek occupation was in fact at its height about 1050 C.E., it coincides with one of a series of decadal-long droughts in the region, says Benson. “There is a 20-year drought in the Four Corners [area] centered at 1050, and it follows a pretty dry period that lasted much longer,” he says.

The match between climate and cultural upheaval becomes even clearer in the next 2 centuries. Benson notes that scientists now consider the mid-12th century megadrought (1135–1180 C.E.) to be the most severe in the past 2000 years. At this time, the Anasazi abandoned their main hub in Chaco Canyon in present-day New Mexico and started bunching together in Mesa Verde's cliffs in Colorado. There, “average precipitation during this drought was reduced by 11%, with some years seeing a reduction in the mean of approximately 50%,” says Benson.

A century later, at about the time the next persistent drought (1276–1299 C.E.) is over, both the Fremont and Anasazi are gone from their ancestral homelands. “In some sense, the 13th century drought may have simply ‘finished off’ some cultures that were already in decline,” Benson and his co-authors wrote earlier this year in Quaternary Science Reviews.

Those droughts went beyond the Southwest, impacting much of the contiguous United States, he says. A close reading of the drought index shows that the mid-12th century drought “was impacting the Midwest, from Illinois, all the way to the coast of California,” says Benson. “The climate is causing crops to fail in the Four Corners where the Anasazi were based, and in Utah, where the Fremont lived; and it is probably also causing crops to fail in the Mississippi valley.”

The impact was all the harder because of the previous and intervening wet years, researchers suspect. There's evidence that after each drought the Fremont rebounded as climate improved. “Each time they did that, there seems to be a population boom,” says Steven Simms, a Fremont scholar and archaeologist at Utah State University in Logan. But those extra mouths to feed demanded more crops, leaving the culture even more vulnerable to the next dry spell. Other climate change forces may also have been at work, including a cold period in the 900s and in the late 1100s suggested by a new analysis of pollen data, says archaeologist Timothy Kohler of Washington State University in Pullman. For the Fremont, eking out a living in an environment already marginal for agriculture, an earlier frost and shorter growing season would have been yet another major hurdle.

To some, all this adds up to a persuasive case for climate change. “I think the evidence for drought as a forcing mechanism is starting to get pretty obvious,” says archaeologist Michael Berry of the U.S. Bureau of Reclamation in Salt Lake City, one of Benson's co-authors. “It's not just a factor. It's a forcing factor.”

If a deteriorating climate triggered food shortages, some researchers speculate that social disorder resulted. “It starts to tear at the social fabric,” says Simms. “That's why late in the record, like in Range Creek, you see these granaries perched way up in the cliffs. It's very much like when you get an oil embargo and you get fistfights at gas stations.”

Other experts agree and say that this kind of climate-triggered chaos may have reverberated on a larger scale across the Southwest in the 1200s. “If the crops aren't working, you might start blaming your rain priests or your ideology,” says Jeffery Clark, an archaeologist at the Center for Desert Archaeology in Tucson, Arizona.

But the Fremont were such generalists, switching from farming to foraging so easily, that other researchers argue that the megadroughts alone wouldn't have killed them off. “It had to be a combination of circumstances that caused this culture to end after 1000 years of success,” says Simms. “It can't just be drought. They weathered those before.”

That's why many southwestern archaeologists favor a mix of environmental and social causes. “Environment is always a factor,” says archaeologist Carla Van West of the SRI Foundation, a New Mexico-based historic preservation organization. “The question is whether it is a causal, proximate, or an ultimate cause.”

Archaeologist Christy Turner of Arizona State University in Tempe has hypothesized that brutal social and political control, a kind of religious terror, was exported into the American Southwest from Mexico about 900 C.E., when evidence of cannibalism starts to show up in the Four Corners region (Science, 1 August 1997, p. 635). Turner speculates that the practice spread like a virus and eventually caused populations to splinter and coalesce in defense, until they eventually collapsed.

Yet other scientists find the climatic evidence hard to argue against. Says Julio Betancourt, a USGS paleoclimatologist based in Tucson, Arizona: “If you have three or four corn crops in a row failing, they're going to be a dead people; they're going to starve to death. You can bring culture all you want into the picture; it's not going to matter.”

That the Cahokia's great mound-building culture in the Midwest collapsed at the same time as the Anasazi and Fremont strikes some as beyond coincidence. Says Boomgarden: “It almost seems like the link has to be climate, because populations that far apart shouldn't have much to do with each other.”

As research on these cultures continues, Range Creek, because of its archaeological and ecological purity, is expected to provide a crucial piece of the puzzle. Next summer, Coats wants to scale the ridgeline across the canyon to search for additional cliff-top dwellings. “I'm convinced there will be more sites up there,” he says. By then, Metcalfe, who plans to expand excavations to include several sky-high sites, hopes to have the tree-ring history of Range Creek in hand, revealing precisely when the drought struck the canyon.

Still, exactly why the Fremont and other cultures sought refuge in the cliffs may elude researchers for some time. Says Spangler: “Is it warfare for warfare's sake? Is it warfare because of environmental stress because you can't produce enough food? There are multiple lines of evidence for each argument.”

7. MALARIA

# Did They Really Say ... Eradication?

1. Leslie Roberts,
2. Martin Enserink

The malaria world is all abuzz about a call by Bill and Melinda Gates to wipe the scourge from the planet. Even if it proves unfeasible, their idea could have a big impact

SEATTLE, WASHINGTON—When Bill and Melinda Gates had finished their back-to-back speeches, many researchers could barely believe what they had just heard. At a meeting hosted by their charitable foundation in their hometown, the couple had uttered the long-forgotten e-word, calling for a sweeping new plan to eradicate malaria.

At first, some thought the philanthropists had misspoken. Very few people have talked about eradicating malaria since an earlier program crashed and burned in the 1960s, leaving a permanent smudge on the field and resulting in a resurgent epidemic across much of the globe. Malaria now kills more than a million people a year, and some malaria experts say eradication, although a noble goal, is simply unachievable. Yet the speeches delivered at the Gates Foundation Malaria Forum on 16 to 18 October leave no room for doubt: The couple wants the malaria parasite to go the way of the smallpox virus.

The second surprise came after the speeches, when Margaret Chan, director-general of the World Health Organization (WHO) in Geneva, Switzerland, jumped up, grabbed a microphone, and enthusiastically seconded the idea. “I pledge WHO's commitment to move forward, and I dare you all to come along with us,” she said, reportedly without consulting some of her senior lieutenants.

Chan and the Gateses were careful not to set a target deadline, presenting eradication as a long-term vision, not a near-term goal. “Multiple decades” is what Bill Gates told reporters afterward, noting that it is “dangerous” to offer anything more concrete. “They both hope it will happen in their lifetimes,” says Regina Rabinovich, head of infectious diseases at the Gates Foundation, who is intimately involved with the plan. Even with those caveats, the call has ignited a debate on whether it is wise—given a long history of broken health promises—to dangle potentially unattainable goals before the public. “There is a danger of overpromising and underachieving,” says Joel Breman, senior scientific advisor at the Fogarty International Center at the U.S. National Institutes of Health in Bethesda, Maryland.

But at the same time, the daring call is having a major impact. Bolstered by already-plummeting malaria rates in several countries, a group of informal advisers has formed a kitchen cabinet of sorts, loosely composed of heavyweight scientists and senior officials from the big funding agencies in malaria, to try to turn the lofty vision into reality—or at least see how far they can get. “It has galvanized the community and created quite extraordinary momentum,” says Rajat Gupta, chair of the board of the Global Fund to Fight AIDS, Tuberculosis, and Malaria, who is a member of that group.

The Roll Back Malaria (RBM) Partnership, composed of all the major players in malaria, including the endemic countries, has already lent its support. Meeting in the Ethiopian capital, Addis Abeba, last week, the RBM Board agreed to set up a high-level steering committee to coordinate efforts and devise a “business plan” within 6 months. No new funding has been announced, but everyone expects the Gateses to put large sums of money where their mouths are.

## Reality check

In the wake of the Seattle meeting, proponents have been trying to reassure skeptical scientists and manage expectations, in part by de-emphasizing the importance of words. Scientists use “eradication” to mean that a pathogen no longer exists anywhere on Earth—save for perhaps a few lab freezers—and control measures can stop. “Elimination” means a pathogen is no longer transmitted in a defined geographical area, although “imported” cases may still occur. By those definitions, malaria has been eliminated in Europe, measles in the Americas, and polio in most countries of the world—but smallpox remains the only disease that has been eradicated.

“I like the term ‘elimination’ better” than eradication, Chan told Science in Seattle, shortly after the Gateses issued their call. “Eradication is of course the ultimate goal, and I don't mind people using [the words] interchangeably. … It is elimination-slash-eradication, depending on the availability of tools.”

Theoretically, there's little doubt that malaria could be eradicated, because there's no animal reservoir from which the disease could bounce back into the human population after it's gone. Nicholas White of Mahidol University in Bangkok believes eradication is already within reach using the latest weapons, such as long-lasting insecticide-treated bed nets, powerful new drugs called artemisinin-based combination therapies (ACTs), and indoor insecticide spraying (Science, 26 October, pp. 556 and 560). Where these weapons have been mass-introduced, malaria is retreating fast, says White.

But most others, including Bill and Melinda Gates, say that although current methods can eliminate malaria in some areas, they won't suffice for global eradication; more powerful ways to break the transmission chain are needed in the hardest-hit areas. “We do not have the tools that are needed to complete malaria eradication today,” says Rabinovich.

That's one key distinction that sets this initiative apart from the previous failed eradication effort, says Carlos “Kent” Campbell, former head of the malaria branch at the U.S. Centers for Disease Control and Prevention in Atlanta, Georgia, and now at PATH, a Seattle, Washington-based nongovernmental organization, where he directs the Malaria Control and Evaluation Partnership in Africa program. That earlier effort, which was abandoned in the late 1960s, relied on DDT to wipe out the mosquito vector and on chloroquine to treat the disease, only to see the vector and parasite develop resistance to both.

The Gateses outlined a two-part strategy: Go as far as you can with existing tools while simultaneously investing heavily in new ones. The latter would likely include transmission-blocking vaccines and drugs; new, preferably single-dose, drugs to replace ACTs when they inevitably are rendered ineffective by resistance; and alternative insecticides and even nonchemical means to defeat mosquitoes, such as traps or genetic modification, along with rapid diagnostics and monitoring for resistance—none of which exists today. The “beauty of this approach,” as opposed to the earlier one, says Campbell, “is that it links a very specific research agenda with a control agenda.”

Existing tools would be massively scaled up over the next 3 to 5 years, says Gupta of the Global Fund. The goal, he says, is to “reduce dramatically, or even eliminate, mortality from the disease and reduce the number of new infections to much smaller numbers.” The first step, he says, will be to bolster country programs, then to scale up regionally and finally globally. “The regional approach is very, very important. You can't have a great program in the Zambia and no program in the DRC [Democratic Republic of the Congo]. It doesn't work.” To pull it off, he predicts that donors such as the Global Fund, the World Bank, and the President's Malaria Initiative will need to roughly triple the money now available for malaria control, up to $3 billion or$4 billion a year. Gupta calls it a “no-regrets policy. … It doesn't matter when the science comes along; let's just control as aggressively as possible.”

Although the hardest-hit countries in Africa and elsewhere are the most obvious targets, public health officials should simultaneously start picking “low-hanging fruit,” says Richard Feachem, former executive director of the Global Fund and now head of the Global Health Group at the University of California, San Francisco. By that, he means trying to eliminate malaria from the “natural margins” or edges of the endemic zones, where the disease isn't as entrenched. The result would be a gradual “shrinking of the malaria map.” Such an effort is getting under way in southern Africa, where the 14 members of the Southern African Development Community have declared their intention to eliminate malaria, starting with the southernmost countries of Botswana, Namibia, South Africa, and Swaziland and moving north, says Feachem. Elimination plans are also afoot for archipelagoes such as Vanuatu and the Solomon Islands.

## False hope?

Nobody would argue against any plan that can have a dramatic impact on malaria. Still, whether all these new activities are a prelude to eradication—and whether it's wise to use that term—is under intense debate. Medical entomologist Willem Takken of Wageningen Agricultural University in the Netherlands thinks it's much too early. Recent victories may be more tenuous than some people realize, he says: Already, researchers are seeing an increase in resistance to pyrethroids, an important class of insecticides, in West African mosquitoes. The ACT miracle, too, is bound to fade, and a vaccine has yet to materialize. Talking about eradication now is giving affected countries false hope, he says. Some also worry about what is called the “Gates Effect”—the fact that the Gateses' vast coffers make people reluctant to criticize them or their projects.

At least as important as the push for new tools is a similar investment to improve the weak health infrastructure across Africa, cautions Donald Hopkins, who leads the global Guinea worm eradication effort from the Carter Center in Atlanta. Even with perfect tools, he says, “we would need capability in each village 24/7. That's not there.” Perhaps the biggest challenge, even proponents agree, will be to sustain interest and funding over the long haul. “We are having a difficult time keeping polio eradication going, and it's only been 20 years,” says WHO Assistant Director-General David Heymann, who oversees that effort. Originally targeted for completion in 2000, the campaign has stalled in a few especially tough countries and is having a hard time raising enough money to finish the job. Feachem, too, agrees that keeping up the commitment will be difficult—and paradoxically, more so as the end nears. “It will require exceptional leadership,” he says. “Luckily, Bill and Melinda are young.”

Some say that malaria fighters would do better to take a page from the measles book. Without making eradication an official goal, a sweeping campaign against that viral disease has made impressive strides; just last week, WHO announced a 91% drop in African measles deaths since 2000. Public health officials can hope for eradication—and some certainly do—but they don't have to worry about a backlash if the remaining centers of infection turn out to be impossible to mop up.

But others say what's important is to focus on the big picture. “I think there will be good to come out of this even if malaria eradication proves unachievable in our lifetimes,” says Hopkins. Adds Chan: “We need champions like Bill and Melinda.”

8. PALEONTOLOGY

# Paleontologists Get X-ray Vision

1. Ann Gibbons

By using x-rays generated from a synchrotron, researchers are getting sharper views of everything from Neandertal teeth to dinosaur embryos

GRENOBLE, FRANCE—On a crisp morning in October, three museum curators crowded into an experimental station on one of the world's most powerful synchrotron particle accelerators. As electrons spun around a giant circular ring nearby and vacuum pumps hummed in the background, the curators painstakingly unveiled the precious fossils they had escorted here from Berlin, Tel Aviv, and Zagreb. “This is my baby, my third son,” said Almut Hoffmann, a historian from the Museum for Pre- and Early History in Berlin. She was still a bit wary of handing over the jawbone of a 40,000-year-old teenage Neandertal from Le Moustier, France. “I heard they will not damage it,” she said nervously.

French and American researchers spent months convincing Hoffmann and two other curators that it was safe to bring their “babies” to Grenoble to be x-rayed by a beam so powerful it would kill a living human within an hour (and cause cancer-causing mutations within a few seconds). These prehistoric youths lived short, obscure lives, but in death they are much in demand: Daily growth lines in the enamel of their teeth offer an unparalleled record of ancient life history and the evolution of childhood. These lines could show whether Neandertals grew up slowly as modern humans do or more rapidly as apes and early human ancestors did.

A couple of brave curators recently allowed researchers to slice open three Neandertal teeth to read the record of these lines, although the results are conflicting (see sidebar, p. 1547). Now the 52 kilo-electron-volt synchrotron x-ray beam used at the European Synchrotron Radiation Facility (ESRF) allows researchers to detect daily rhythms without cutting or damaging teeth—and so to gather data on many specimens. “Before this technique, the only way we could see this much detail inside was to cut the tooth,” says paleoanthropologist Tanya Smith of the Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany. “No other scanner in the world has been adapted to do this.”

Grenoble is one of just three large third-generation synchrotrons in the world and the only one adapted for viewing large fossils so closely. So far, it has uncovered new species of ants and beetles trapped in opaque amber, revealed dinosaur embryos encapsulated in eggs, and explored rodent and primate teeth. “It's an entirely new technique for paleontology,” says paleontologist Philip Donoghue of the University of Bristol in the U.K., who began using the lower energy Swiss Light Source synchrotron in Switzerland on fossils 3 years ago (Science, 13 October 2006, p. 291). “Synchrotron tomography allows us to look at new areas of science without destroying fossils.” Other synchrotrons in Europe and China are now gearing up to image fossils, too.

The track record of the synchrotron in Grenoble for not damaging fossils finally convinced curators to gather there for 8 days in October, bringing fossils of Neandertals and modern humans that died tens of thousands of years ago in caves in Croatia, France, and Israel.

The paleontologist who made this possible is Paul Tafforeau of ESRF. He started as a graduate student in paleontology at the University of Montpellier in France, where he was unhappy about destroying primate teeth to study their enamel. He began working at ESRF “by accident” after a conversation in 2000 with the head of the imaging group, José Baruchel. He quickly realized the potential of the nondestructive imaging tool, which has four times better resolution than the best conventional computed tomography (CT) scanners that image large fossils. Although his first tests failed, he began working with the imaging group to produce three-dimensional (3D) images of the internal microstructure of primate teeth.

The beauty of the synchrotron is that it produces x-rays that are far more spatially coherent than beams from conventional CT scanners, so the waves of x-rays are tightly in sync when they pass through an object. This coherence is essential for phase-contrast imaging, which allows researchers to see not only how different densities of material in a tooth absorb the x-rays but also how the passing x-ray's wavefront is modified by the electronic structure of the sample. This method exposes even more detail about tooth microstructures smaller than the width of a single cell, Tafforeau and Smith reported online in the Journal of Human Evolution on 28 November.

ESRF is also the only synchrotron that can scan larger objects, such as complete hominid skulls, at a 45-micrometer resolution (the width of a hair). By taking radiographs of a sample that rotates 180° or 360° during a 2-hour run on the beamline, the team can use software to produce a stack of cross sections that generate a precise 3D image. The cost for the 8-day run on hominid teeth: \$120,000, in this case underwritten by ESRF.

So far, Tafforeau and colleagues have used the synchrotron to expose the internal structures of fossil green algae and an unerupted premolar in an extinct primate, among other fossils featured in Applied Physics in 2006 to demonstrate the method. Detailed new images of dinosaur embryo bones are “truly spectacular and cause a stir every time they are shown at a scientific meeting,” says paleontologist Eric Buffetaut of the Centre National de la Recherche Scientifique in Paris.

Tafforeau was recently hired full-time at the synchrotron to focus its x-rays on more fossils. Specimens that recently vied for precious time on the beamline include Cretaceous mammals encased in rock, dinosaur and bird embryos, snails, rodent skulls, Mesozoic crocodile coprolites, and the skull of the earliest proposed hominid, Sahelanthropus tchadensis. Such large fossils present new challenges compared with the tiny rodent teeth or insects in amber. And then there are the unexpected surprises. “Le Moustier has crashed,” announced Tafforeau as imaging of Hoffmann's specimen began. The fossil shifted just 5 micrometers on its pedestal of wax, and the plaster used to restore the fossil absorbed too much of the beam, making phase-contrast imaging difficult.

As the week progressed, Tafforeau, Smith, and colleagues worked around the clock to use every minute of beam time. They had better luck with a jawbone of a Neandertal from Krapina, Croatia, which produced sharp images that can be contrasted with those of an early modern human from Qafzeh Cave in Israel. But the answer to their question—how fast these Neandertals grew up—won't be known until after the team has analyzed many terabytes of data.

Paleoanthropologist Jean-Jacques Hublin of the Max Planck Institute for Evolutionary Anthropology watched the images flashing up on a bank of computer screens in the control room and reflected on the march of technology during his lifetime. “When I started my career in paleoanthropology, we used only calipers and a camera,” he said. “I never imagined then that we shall time the development of a Neandertal with an accelerator.”

9. PALEONTOLOGY

# Dental Evidence Suggests Neandertals Matured Faster Than We Do

1. Ann Gibbons

Paleoanthropologists eager to compare the development of Neandertals and modern humans waited for years to be allowed to take a slice out of a Neandertal's tooth to see the minute daily growth lines inside. “We await a brave curator somewhere who will allow a single Neanderthal tooth to be sectioned; much depends on it,” paleoanthropologist B. Holly Smith of the University of Michigan, Ann Arbor, wrote in an article in Evolutionary Anthropology in 2004.

Smith has gotten her wish recently, but with mixed results. A study in Nature last year of two sliced Neandertal teeth found that the teeth formed slowly, like those of modern humans. But this week in the Proceedings of the National Academy of Sciences (PNAS), researchers analyzed growth lines in a sliced Neandertal molar plus other uncut teeth from the same specimen. They conclude that this 8-year-old Neandertal from Belgium grew up more rapidly than modern human children, according to lead author Tanya Smith (no relation) of the Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany. “I think it's pretty convincing,” says paleoanthropologist Jay Kelley of the University of Illinois, Chicago. But he notes all the same that the paper provides “data for [only] one individual.” Data on more Neandertals may be able to resolve the problem this year, thanks to a new method for seeing growth lines without damaging specimens (see main text).

Researchers have known for some time that humans are the only animals to have extended their childhoods long enough to have a teenage phase. Homo sapiens grew up twice as slowly as apes and our australopithecine ancestors that lived 4 million to 2 million years ago, says Holly Smith. Our ancestors may have lengthened childhood and delayed reproduction to allow more time to develop their brains, perhaps improving social learning, language, and other behaviors.

But researchers do not know when this dramatic change in life history strategy took place in the human family. Were H. erectus parents 1.8 million years ago the first to experience the joys of teenagers, or did adolescence appear 500,000 years ago in a common ancestor of Neandertals and modern humans? A previous report in PNAS by Tanya Smith suggested that it was even later.

The best way to find out is to look inside the teeth of Neandertals, modern humans, and their ancestors. Like rings in a tree, teeth grow incrementally, preserving a record of their development in microscopic lines in their enamel. These lines are deposited daily, along with less frequent lines that reveal stresses such as birth. And longer-period lines can be seen on the surfaces of teeth. In the new study, Tanya Smith took a thin section of an upper molar and counted the number of daily lines laid down before and after birth and between long-period lines. This told her how many days passed between the longer-period lines. She could then use the external lines on the uncut teeth to calculate how much time passed before their roots and cusps formed completely, as well as to determine the timing of key developmental benchmarks. She found, for example, that the second molar erupted a few years earlier in this 8-year-old Neandertal than in H. sapiens, suggesting that Neandertals grew up faster than we did.

That conclusion contradicts the earlier study of a Neandertal, done by Christopher Dean of University College London and colleagues. Given the conflicting reports, the next step is to analyze more specimens. “Dental evidence from a larger number of individuals … would go a long way toward clinching the claim that they were distinct in the way they grew up,” says Dean. That is precisely what Tanya Smith and her colleagues are trying to do with their new x-ray vision in Grenoble.