# News this Week

Science  01 Jun 2001:
Vol. 292, Issue 5522, pp. 1622
1. ECOTERRORISM

# Arson Strikes Research Labs and Tree Farm in Pacific Northwest

1. Robert F. Service

PORTLAND, OREGON—It was a costly case of guilt by association. Last week the labs of plant geneticist Toby Bradshaw and his colleagues at the University of Washington (UW), Seattle, suffered $3 million in damage from a fire believed to have been set by opponents of genetic engineering in plants. But the fire wound up destroying research —in areas such as understanding how poplar trees fight disease and restoring wetlands— that uses traditional plant-breeding methods and mainstream ecology, not the types of activities normally targeted by ecoterrorists. On the same day, arsonists also destroyed two buildings and vehicles at Jefferson Poplar Farms, an Oregon tree farm 95 kilometers northwest of Portland that uses traditional techniques to improve the stock. Some scientists see the scale of the two attacks, which authorities suspect were related, as a worrisome sign that ecoterrorists are increasingly moving beyond fighting agribusiness and many forms of commercial development to attacking fundamental research. As Science went to press, no group had yet claimed responsibility for the two blazes, which occurred around 3 a.m. on Monday, 21 May. But an undamaged building at the Oregon tree farm was spray painted with the letters “ELF” along with the message “You cannot control what is wild.” ELF stands for the Earth Liberation Front, a loose-knit ecoterrorist collective that has claimed responsibility for some of the many illegal acts reported in recent years (see table). Some researchers say that last week's incidents have left them feeling more vulnerable. “Toby [Bradshaw] has no direct connection to commercial research,” says Steve Strauss, a plant geneticist at Oregon State University in Corvallis, whose own work on transgenic trees was the target of vandals (Science, 6 April, p. 34). “Their message is, ‘We don't even want research, [because] it is an act against God.'” The UW blaze gutted Merrill Hall, which housed research and office space for eight faculty members in the university's Center for Urban Horticulture. According to UW police chief Jon Brouelette, the fire was started in Bradshaw's ground-floor office. The Oregon fire targeted Greenwood Resources, a company that sells fast-growing poplar trees to paper producers. According to Greenwood's president, Jeff Nuss, the company uses only traditional hybrid breeding techniques to create trees with enhanced disease resistance, better wood quality, and other beneficial traits. Bradshaw, whose work on poplar trees was also targeted by vandals 2 years ago, says he believes the UW fire was set by someone familiar with his professional activities. As evidence, he points to a pair of boxes from his office that were found in a field outside Merrill Hall. The boxes normally house two oddly colored corn snakes that Bradshaw uses in lectures to illustrate the genetics of color inheritance. The snakes were actually at Bradshaw's home at the time of the fire. “That wasn't just a coincidence,” says Bradshaw about what appears to have been a misguided attempt to save the snakes from the fire. For the past 15 years, Bradshaw has tried to pinpoint genes that control branch development, resistance to disease, and tolerance to cold temperatures, as well as other environmental stresses. In one soon-to-be- published study, for example, Bradshaw and his colleagues identified the general region in poplar tree DNA that contains a gene that confers resistance to poplar leaf rust, a fungal infection that kills the tree's leaves and stunts its growth. The group hopes to isolate the gene and learn what it produces to fight off the fungus. Bradshaw says he uses only traditional plant-breeding methods in these and other studies. But an ELF spokesperson has criticized Bradshaw for accepting research funds from tree-farming companies, saying that the results could be used to genetically engineer trees. View this table: The apparent attempt to snuff out Bradshaw's research claimed some of the greenest research on the UW campus. In addition to Bradshaw's work on poplars, projects at the center focus on restoring damaged wetlands, conserving rare and endangered plants, charting life's recovery following the 1980 eruption at nearby Mount St. Helens, teaching people to grow their own food in backyard gardens, and understanding the genetics of how new species develop. “All of that is collateral damage to my work on poplars,” Bradshaw says. Certain items lost to the fire were irreplaceable. One, a tissue culture collection of 100 endangered showy stickseed plants, was particularly distressing to lose, because only about 300 plants are believed to exist in the wild. In a library adjacent to Merrill Hall, about 20% of the books—many of them rare and out of print—were also destroyed, according to Tom Hinckley, an ecosystem scientist and head of the horticultural center. Despite these losses, the university has made it clear that the attacks won't stop research and outreach efforts. Hinckley says officials have promised to “do what it takes to get us back on our feet.” Merrill Hall's research and office space will be rebuilt, he adds; in the meantime, faculty members and students are moving into temporary research and office space. “Even though [the fire] was intended to slow or stop work, it won't have that effect,” says Bradshaw. As for future attacks, Brouelette says that his office will likely step up security at agricultural research sites. But he and others say that the value of additional protection must be weighed against the need for a public institution to remain accessible. “A fortress mentality doesn't serve academic freedom well,” says Hinckley. Welcome or not, such a feeling is already beginning to permeate agriculture science, says Strauss. “It's terrible. There is less openness, less willingness on the part of researchers to discuss their work, and “therefore less ability to discuss merits and concerns to others,” says Strauss. Teaching suffers as well, he adds, because concerns about security have curtailed the presence of undergraduates at field sites. Still, he and others believe that the work must continue. “The alternative is to let terrorists dictate what we do,” says Strauss. 2. PALEONTOLOGY # New Dig at Old Trove Yields Giant Sauropod 1. Erik Stokstad When Allied bombers descended on Munich in the spring of 1944, they destroyed much of the city—including the Bayerische Staatssammlung museum. Among the treasures reduced to rubble were Cretaceous bones collected from Egypt by Ernst Stromer von Reichenbach. More than 50 years later, when Josh Smith, a grad student at the University of Pennsylvania in Philadelphia, was casting about for a Ph.D. topic, he drew up a wish list—places to dig that weren't being actively excavated but had a history of interesting discoveries. Topping his list were the sites discovered by Stromer. In February 1999, Smith set out to find Stromer's sites. It required sleuthing and luck, but on page 1704, Smith and his colleagues describe the first land vertebrate to be excavated from the sites since Stromer published his last monograph in 1936. Their find, Paralititan stromeri, is a new genus of sauropod dinosaur, estimated from its incomplete skeleton to be the second most massive known. It also marks the first time a sauropod has been linked to a mangrove-rich habitat. The locality was highly diverse during this part of the Upper Cretaceous, about 95 million years ago. So even more important than the sauropod itself is the reopening of Stromer's sites: Experts say that having more land species from this part of Africa will help nail down ideas about the breakup of the supercontinent of Gondwana. Stromer first arrived in Egypt in 1911. After trekking 390 kilometers southwest of Cairo by camel, his field party searched a broad expanse known as the Bahariya Oasis. During the Upper Cretaceous, the area appears to have been a coastline bordered by mangrove swamps and tidal channels. After a few field seasons, Stromer had found as many as 40 genera of fish, crocodiles, dinosaurs, and other creatures. But all of the terrestrial vertebrates he brought back to Germany were destroyed in World War II, except for two skulls smuggled out by curators. Smith and his party faced a problem in trying to find the source of the fossils: Stromer hadn't left directions or even published any maps or photos of the sites he quarried. Still, they had one clue: A friend of a team member located old scientific literature in Cairo with descriptions of prominent landforms in the Bahariya Oasis and geographic coordinates of one of Stromer's quarries. Then came a stroke of luck. Smith entered the wrong coordinates into his Global Positioning System receiver. So when the scientists set out in their 1998 Toyota Land Cruiser—no camels for this group—they ended up far from the landmarks. To get oriented, Smith stuck his head out the passenger window and spotted a large sauropod bone. “It was total serendipity,” he says. Smith snapped some photographs, noted the location, and kept searching. The next year, Smith and his fellow grad student Matt Lamanna assembled a crew to excavate the sauropod remains. They pulled out 6.5 tons in 3 weeks. Based largely on features of the vertebrae, they identified the incomplete skeleton as that of a titanosaurid, the dominant group of sauropods during the Cretaceous. They also came across a dig site about 10 kilometers away that may have been worked by Stromer. In a spoils pile they uncovered old boots, pieces of tin cans, and a piece of German newspaper printed in what looked like a pre-World War II typeface. Stromer himself had discovered a titanosaurid in the area, which he named Aegyptosaurus. But the pronounced ridges on the freshly excavated 180-kilogram humerus, as well as a bony projection on the shoulder blades, suggested that the specimen belonged to a new genus. Smith's team named it Paralititan, after the term “paralic,” which describes tidal environments like mangrove swamps. To figure out how large Paralititan was in life, the researchers stacked its 1.7-meter-long humerus against that of Argentinosaurus, a South American titanosaurid that's the largest on record. Because the humerus isn't preserved in Argentinosaurus, the team first had to estimate its length from comparisons with other titanosaurids. Argentinosaurus's humerus, estimated at 1.81 meters, makes Paralititan the next heaviest known titanosaurid, perhaps twice the size of Stromer's adult Aegyptosaurus. The thought of Paralititan weighing as much as 100 tons raised a concern: Would it have sunk into the mangrove swamp. Team member Kenneth Lacovara, a coastal geologist at Drexel University in Philadelphia, crunched some numbers. Given feet 1 meter in diameter, there was no problem—a relief for the paleontologists, who didn't think the massive carcass could have floated in or been dragged there by predators. “I'm confident that this sauropod may have spent a fair amount of time in the mangrove,” Lamanna says. The researchers have also found new specimens and taxa of fish, sharks, turtles, marine reptiles, lizards, and other dinosaurs. They plan to go back next year to look for even more. Ultimately, a diverse array of Upper Cretaceous fossils from North Africa could help determine the relative positions of Africa, South America, and Europe. Decades ago, Stromer first discovered that diversity, only to see his collection blown to pieces. “It's a great shame it was lost,” says Paul Upchurch, a sauropod expert and biogeographer at Cambridge University, United Kingdom. “But now that Josh Smith and colleagues have shown that there still is material to be found there, at least we have a second bite at the cherry.” 3. AUSTRIAN UNIVERSITIES # Scientists Spar Over Reform Plan 1. Min Ku* 1. Min Ku is a science writer in Bern, Switzerland. With reporting by Robert Koenig. VIENNA—The Austrian government earlier this week approved plans for a major shakeup of the country's university system. Proponents say the proposal, if approved by Parliament, would infuse fresh blood into a system that has become sclerotic. Some critics, however, are angry over a loss of permanent jobs, while others charge that the reforms will be half-hearted and underfunded. Most Austrian researchers agree that the university system is ailing. Over the past few decades, it's been “too easy to get permanent positions without a real assessment of the achievements of the candidates,” says University of Vienna quantum physicist Anton Zeilinger. Adds University of Innsbruck physicist Peter Zoller, “there are essentially no positions left for young people.” Compounding the problem, most professors and assistants are civil servants, or Beamte, a status that confers lifetime employment and regular raises not tied to job performance. Particularly acute is the plight of young researchers. Whether they are allowed to do independent research is largely up to the senior professor supervising their work, says University of Linz physicist Reinhard Folk, who says “there is a lot of misuse of people.” Arnold Schmidt, president of the Austrian Science Fund, the country's main granting agency, points out that many researchers are “too old” by the time they are permitted to do independent research. Such disheartening conditions, if allowed to fester, will cause Austria “to lose a whole generation of scientists,” warns University of Graz neuropharmacologist Peter Holzer. In response to these widespread complaints, education and science minister Elisabeth Gehrer last December proposed legislation that would abolish civil servant status for all new university professors and assistants. Under her plan, only senior professors would retain permanent positions. So-called assistants would be reclassified as doctoral students, 6-year postdocs, or junior professors. Gehrer also proposed making Habilitation—a lengthy apprenticeship necessary to apply for a professorship—optional in view of the extra-long postdoc stint contemplated under the plan. That would bring Austria in line with Germany, which is phasing out Habilitation over the next decade. In April, Gehrer sent the legislation out for review. The reforms are on a fast track to take advantage of an expected wave of retirements over the next 5 years, when an estimated 500 professors—25% of those now working—will leave academia. But it hasn't worked out quite as Gehrer hoped: After the review process ended on 18 May, the plan came under fire from several directions. Most deferential was the Federal Conference of Professors, which represents senior professors. It said the reforms were fine— except for the optional status of Habilitation. The Federal Conference for Academic and Artistic Personnel (BUKO), representing 7500 university assistants, also criticizes that aspect. “Habilitation will not be formally necessary, but it will probably be difficult to find a job without it,” argues Folk, BUKO's chair. The changes “will still keep young scientists dependent.” He suspects that the real intention is to cut costs—a view that Gehrer rejects. “Saving money is not a goal at all,” she says. “The main goals are to achieve more mobility, higher quality education, and harmony with European standards.” Meanwhile, the Austrian Rectors' Conference has rejected the proposal. While supporting reform in principle, the rectors contend that the government has provided no clear funding for the plan, which they estimate will cost universities an extra$6 million per year to implement, partly from increased benefits to employees who are not civil servants. The rectors also objected to a proposed $76,000 cap on annual salaries for professors, arguing that it would reduce their ability to retain talented researchers. The civil service union took perhaps the hardest line. Last week, it threatened a 1-day university strike, forcing 11th-hour negotiations between the union and the science ministry. The union won some concessions: The latest version of the legislation will allow universities to hire permanent “staff scientists” according to their needs and to grandfather researchers now undergoing Habilitation into permanent positions. In addition, the ceiling on professor salaries has been raised to$112,500.

On 29 May, the Federal Cabinet approved the plan and sent it to Parliament, where the government is banking on its majority to pass the legislation by the end of next month. Even if that happens, many people view the reforms as a work in progress. They “are a step in the right direction [but] don't go to the heart of the matter,” says Kim Nasmyth, director of the privately funded Institute for Molecular Pathology in Vienna. “The fundamental problem is that no one is in a position of power to organize resources and get professors to cooperate. Nobody is controlling the professors,” he insists—and the new law won't change that.

4. SPACE RESEARCH

# ESA Embraces Astrobiology

1. Helen Gavaghan*
1. Helen Gavaghan writes from Hebden Bridge, U.K.

FRASCATI, ITALY—For years, European astrobiologists were a fragmented bunch, largely isolated from one another. That all began to change in April 1999, when some of Europe's top astrobio guns, relaxing over a beer in a bar after a geophysics meeting in The Hague, decided to band together. From that chance get- together emerged the 120-scientist-strong European Exo/Astrobiology Network, which met last week for the first time here in this central Italian city as well known for space research— it hosts a major institute of the European Space Agency (ESA)—as it is for its crisp white wines.

The gathering proved to be more than a coming-of-age party for Europe's fledgling community of exo/astrobiologists. At the workshop, the ESA unveiled an ambitious agencywide strategy for exo/astrobiology called Aurora that the agency intends to present to its governing council this fall.

Aurora is envisioned as having two goals: searching for extraterrestrial life, such as fossil microbes on Mars, and precursor molecules to life on Earth; and laying the groundwork for future human space exploration. “If we decide it is right in 20 years' time to send people to Mars or an asteroid, we must find out now what knowledge and supporting technology we would need,” says Didier Schmitt, head of life sciences at the ESA's Space Research and Technology Centre in Noordwijk, the Netherlands.

To support both goals, ESA argues that expertise must be drawn from both the Space Science and the Manned Spaceflight and Microgravity directorates, traditionally quite separate. Aurora will build on programs approved or under discussion in these directorates, assessing them through the prism of exo/astrobiology.

According to ESA, the solar system targets important for exo/astrobiology are Mars (ESA and member states already are preparing missions to Mars either alone or in collaboration), asteroids, Jupiter's moon Europa, and Earth's moon. In particular, the agency's science advisers are keen to see the agency begin a study on a Mars sample-return mission, although such a mission would be needed only if French plans to work with NASA on such a mission collapsed.

Having first broached the idea last November, ESA is moving with uncharacteristic speed to launch Aurora. It hopes to have a fleshed-out proposal to present to science ministers from member states this November. During a 3-year preparatory phase, ESA officials are looking to raise about $30 million for feasibility studies for a detailed exo/astrobiology program and to identify technologies needed to initiate programs. If Aurora becomes a fully fledged program, ESA will look to ministers for up to$130 million a year to fund it.

The network's leaders, who helped advise ESA on its plans, intend also to ramp up fund- raising efforts at national research agencies and the European Commission for ground-based as well as space-based studies. “The time is right,” argues the network's newly elected president, André Brack, a research director at the molecular biophysics laboratory of CNRS, the French national reseach agency, in Orleans. “Ten years ago, there were no good chemical and physical arguments for life being anything other than entirely homegrown,” he says. “Now we know of extrasolar planets, of complex organic molecules in interstellar clouds, of micrometeorites depositing carbon on Earth, and of microbes living in extreme environments, and there is evidence of water on Mars and on Jupiter's moon, Europa.”

The budding pan-European approach to exo/astrobiology builds on efforts in individual nations. In France, for example, the nation's space agency and CNRS in 1999 formed a federation of 50 exo/astrobiology labs that ended their isolation. Spain has gone a step further, in 1998 launching the $8.6 million Centre for Astrobiology in Madrid, and the Italian Space Agency, for the first time, will have a specific line for exo/astrobiology in its 2002 budget. (The amount is under discussion.) But in spite of this apparent enthusiasm for exo/astrobiology, the prospects for Aurora are uncertain. ESA may have a hard time extracting the additional money from member states, which are already tightfisted when it comes to ESA's regular budget. “There are many difficulties to resolve at ministerial level,” admits ESA's Schmitt, who told workshop participants that the agency is seeking the backing of the scientific community on Aurora—something that will be essential for making a strong case to the ministers this fall. 5. U.S. CONGRESS # New Leaders Emerge After Senate Shake-Up 1. David Malakoff A political earthquake has U.S. science advocates scrambling to survey a dramatically altered Washington, D.C., landscape. With Republican Senator Jim Jeffords's (VT) announced defection from his party, control of the Senate will switch to the Democrats. That power shake-up, say science lobbyists, could affect both research budgets and science policy. Last November's elections left the 100-member Senate balanced on a knife's edge, with both parties controlling 50 seats. Republicans had the upper hand, however, because Senate rules allow Vice President Dick Cheney to break any ties. As a result, Republicans claimed the body's top leadership posts and the right to control the legislative calendar, choose committee leaders, and determine the makeup of panels that negotiate differences with the House of Representatives. Now that Jeffords has become an Independent, Democrats will have sway over all those decisions. Senator Tom Daschle (D-SD) is expected to replace Trent Lott (R-MS) as majority leader as early as 5 June; committees will also get new chairs (see table). View this table: In many cases, the key science spending panels are expected to stay the course. Senator Barbara Mikulski (D-MD), an ardent supporter of a bigger budget for the National Science Foundation (NSF), is expected to replace the equally enthusiastic Kit Bond (R-MO) on the panel that oversees NSF and NASA. Similarly, Senator Tom Harkin (D-IA), a leading voice for doubling the budget of the National Institutes of Health (NIH), is in line to succeed fellow doubling advocate Arlen Specter (R-PA) as head of the panel that oversees NIH. Both senators also oppose possible moves by the Bush Administration to ban federal funding for research using stem cells harvested from human embryos. Other committees, however, could see changes in emphasis. Senator Pete Domenici (R-NM), known as St. Pete for his efforts on behalf of Los Alamos National Laboratory and several other large Department of Energy (DOE) research facilities in his state, will likely cede control over DOE funding to Senator Harry Reid (D-NV). Although Reid is friendly to science, he has criticized the planned Yucca Mountain nuclear waste repository in his state, as well as the$3.4 billion National Ignition Facility, a giant laser project at DOE's Livermore National Laboratory in California. Renewable-energy advocate Jeff Bingaman (D-NM) is expected to take over DOE's authorizing committee from Frank Murkowski (R-AK), a friend of the oil and gas industry. That switch virtually assures that the Senate will block controversial portions of the Bush Administration's new energy policy, such as a call to open Alaska's Arctic National Wildlife Refuge to drilling (Science, 25 May, p. 1462). A Democratic Senate is also likely to question Bush's plans to increase funding for missile defense, downplay controls on global warming gas emissions, and cut funding for environmental research.

Whereas most lobbyists are hedging their bets, Michigan State University's Howard Gobstein ventures that a divided government will be good for research. “Support for science is bipartisan,” he says, and the new lineup gives both parties an incentive to take the lead.

6. ULTRAFAST LASERS

# Strobe Light Breaks the Attosecond Barrier

1. Robert F. Service

If you want to see Harm Geert Muller's latest handiwork, don't blink. On page 1689 of this issue, Muller—a physicist at the FOM Institute for Atomic and Molecular Physics in Amsterdam, the Netherlands—along with Dutch and French colleagues reports creating the fastest strobe light ever made, with individual pulses lasting just 220 attoseconds, or 220 billionths of a billionth of a second. These unimaginably short pulses are the first to be confirmed as breaking the attosecond barrier, a goal of high-speed-laser researchers for nearly a decade. Down the road, such pulses may one day serve as an ultrafast camera, allowing researchers to freeze action and perhaps to spot the gyrations of individual electrons whirling around an atomic nucleus.

“This is a great paper,” says Paul Corkum, a pioneer in making short laser pulses and a physicist at the National Research Council of Canada in Ottawa, Ontario. Laser researchers have likely been making trains of attosecond pulses for years, says Corkum. But until now they've had no way to spot such fleeting bursts: Electronic detectors are too plodding and simply record a blur of photons. “How do you know what you've got? That's been the struggle,” says Corkum. Muller and his colleagues managed the feat not by detecting the photon bursts themselves but by tracking their ability to ionize atoms in a nearby gas jet—a technique that Corkum says “works very well.”

Generating the short pulses in the first place is a comparatively simple task. Quantum-mechanical calculations show that if light waves spanning a broad range of frequencies are brought together under the right conditions, they can interact to produce an ultrashort pulse. Muller and his colleagues—including teams led by Philippe Balcou at the National School of Advanced Techniques (ENSTA-École Polytechnique-CNRS) in Palaiseau, France, and Pierre Agostini at the Saclay Research Center of France's Atomic Energy Commission—create this broad range of frequencies by a technique Corkum dreamed up in the mid-1990s (Science, 4 August 1995, p. 634). Starting with a short-pulse infrared (IR) laser that fires pulses lasting just 40 femtoseconds (a femtosecond equals 1000 attoseconds), the researchers split these light pulses and steer one portion toward a jet of gaseous argon atoms; the second portion is used in a later detection step. The intense light ionizes the atoms and generates an oscillating electric field that drives the freed electrons away from their parent atoms and then back again at high speed. Some of the surging electrons smash into their parent atoms, releasing energetic short-wavelength photons across a broad range of frequencies. Most of the photons cancel one another out as the peaks of some line up with the troughs of others, but a few of them—those at odd harmonic intervals of the initial laser light—survive.

Physicists have long calculated that these surviving photons would be produced in a staccato of attosecond pulses. But to confirm that's what they had, Muller's team needed to do two things. One was to get a precise accounting of frequencies produced and the amount of each one, both of which they could track easily with a device called a spectrophotometer. The other was to determine their relative phase, that is, whether the waves and crests marched in lockstep. “That's the key,” says Muller. With the phases and frequencies in hand, the team could mathematically work out the pulse durations.

To get those phases, the French and Dutch researchers came up with a novel scheme. First, they used mirrors to filter out all of the harmonic photons except a band in the ultraviolet (UV) range. They trained the UV beam into a second gas jet of argon atoms. At the same time, the team zapped the gas with the second half of the original infrared laser beam. Under the double bombardment, the argon atoms absorbed photons and kicked out electrons. Using standard detectors, the researchers recorded the number of the electrons and their energy levels. Then they varied the phase of the incoming IR photons by passing them through a glass window that slightly slowed their progress. The changes in the IR phase altered the photons' ability to kick out electrons at different energy levels. By measuring how the distribution of electron energies changed and by crunching some numbers, the researchers were able to work out the phases of both the IR and UV photons that must be present at each position—information that enabled them to confirm the brief but notable life-span of their record-setting pulses.

Muller and Corkum say the next race will be to use the pulses to track the blinding dance of electrons around nuclei, which are too fast for even today's femtosecond lasers to capture. As well, they say researchers will undoubtedly want to slice out single flashes from the attosecond pulse trains and try to shave each pulse down to just 10 or so attoseconds each, the theoretical limit for the methods now being used. “It's something we're working on. But it's still really science fiction at the moment,” says Muller. Until this week, so were 220-attosecond pulses.

7. NEUROBIOLOGY

# Bee Dance Reveals Bee's-Eye View

1. Elizabeth Pennisi

Imagine a driver asked to judge the distance traveled by keeping track of the number of buildings, signs, and lampposts whizzing by. Now ask that driver to tell a friend how far to go based on those visual cues. That's exactly what honeybees do, says Harald Esch, a neurobiologist at the University of Notre Dame, Indiana. For years, bee biologists have argued about whether the dance that honeybees perform when they return to the hive communicates anything more than the general direction of the nectar source. Now Esch and his colleagues have settled this question by tricking a foraging honeybee into communicating the wrong information to its hivemates. The work, reported in the 31 May issue of Nature, shows that “bees really are getting [distance] information from the dances,” says Thomas Seeley, a biologist at Cornell University in Ithaca, New York. The work also confirms that the bee measures distance in terms of “optic flow,” the stream of visual cues encountered along a flight.

Over the past several years, experiments have suggested that honeybees know how far they've gone by how much they've seen—and not, as many researchers had thought, by how much energy they've expended on their trip. In a key experiment, Mandyam Srinivasan and Shaowu Zhang, neurobiologists at Australian National University in Canberra, Jü;rgen Tautz of the University of Wü;rzburg in Germany, and their colleagues tested this idea by training bees to fly down tunnels with different patterns painted inside. They found that the bee danced longer than it should have after flying through a semicheckered tunnel that gave the bee the sense of moving past many, many objects. If the tunnel was lined with horizontal stripes, which had no vertical boundaries to signify an object being passed, the bee's dance was too short. These experiments, coupled with earlier work by Esch, strongly indicated that the bees use the passing landscape to click off the meters.

In this new work, Srinivasan, Zhang, and Tautz teamed up with Esch to see whether a bee actually communicated its misperceptions to other bees. “It's another in a series of very cleverly designed experiments,” comments Mark Frye, a neurobiologist at the University of California, Berkeley. The researchers first set up a tunnel lined with a complex pattern, then trained bees leaving the hive to fly through the tunnel to get to a feeder on the other side. They videotaped the bee's dance when it returned and calculated the distance communicated. The bee danced as if it had traveled 72 meters instead of 11, the true distance. “The bees felt like they had gone a greater distance,” says Frye.

The researchers then stationed themselves 35, 70, and 140 meters away from the hive for 2.5 hours and counted how often bees from the hive flew up to them in search of food. About three-quarters of the 220 bees approached the 70-meter spot looking for nectar—the distance communicated in the dance. Based on these results, says Frye, “there is now no question that the way honeybees communicate distance depends on what they see.”

8. ASTROPHYSICS

# Radical Gravity Theory Hits Large-Scale Snag

1. Charles Seife

La fin du MOND, c'est arrivée—perhaps. For nearly 2 decades, modified Newtonian dynamics (MOND), a heretical theory that alters some properties of gravity to eliminate the need for dark matter, has survived one astronomical observation after another—and even gained strength in the process. But now, physicists at the Institute for Advanced Study in Princeton, New Jersey, have shown that the theory is deeply at odds with observations of galaxy clusters, suggesting that MOND is in trouble.

“I take it very seriously,” says Stacy McGaugh, an astrophysicist at the University of Maryland, College Park, who has supported the theory. “It's a real problem for MOND.”

On one level, MOND is an attractive idea. Astronomers have long been troubled by the motion of matter within galaxies; peripheral stars and clouds orbit the galactic center faster than Newtonian (and Einsteinian) laws of gravity dictate. Most scientists explain the discrepancy by assuming that galaxies are surrounded by a halo of invisible matter, but in 1983 Mordechai Milgrom of the Weizmann Institute of Science in Rehovot, Israel, created MOND as an alternative explanation. He altered the standard rule for gravity so that slowly accelerating objects feel a slightly stronger gravitational pull than Newton's laws dictate. That gives the outer edges of galaxies an extra little tug, causing them to move faster. The tweak reproduced the motion of the galaxies with high precision, without the need for dark matter.

“It's a simple and clear prediction that matched the observations well,” says Anthony Aguirre of the Institute for Advanced Study. “It does seem to succeed miraculously well.” On another level, however, MOND is a very unappealing theory, because mathematicians haven't been able to meld it with the framework of general relativity.

It should come as no surprise that scientists have been taking potshots at MOND for years; however, the theory has survived them surprisingly well (Science, 28 January 2000, p. 572). Indeed, a missing “peak” in microwave-background data (Science, 28 April 2000, p. 595) was briefly seen as a surprising source of support for MOND, although the peak has since been found (Science, 4 May, p. 823). But the tide might now be turning.

Aguirre and his colleagues have analyzed x-ray data from the ROSAT, ASCA, and BeppoSAX satellites to determine the temperature of matter in galaxy clusters. Much of that matter takes the form of x-ray-emitting gas, whose temperature depends on its density, pressure, and acceleration. Those factors, in turn, reveal information about what governs the clouds' motion—dark matter or modified gravity. It turns out that MOND fails the test: The observed temperatures look nothing like what would be expected in a MOND-controlled cluster. The data “disagree very strongly with MOND's prediction,” says Aguirre. “MOND is not a viable alternative to dark matter in clusters.”

“There is a conundrum,” Milgrom admits, although he notes that he has known about problems with galaxy clusters for some time. Additional unseen matter, like the once-unknown x-ray-emitting gas throughout the cluster, might account for the discrepancy, he says. “There is always room for yet-undetected matter,” he says.

To Aguirre, this is an unsatisfying solution. Unseen matter, he points out, smacks of the very problem MOND was designed to avoid. Soon, observations of the cosmic background radiation—precise measurements of a third “peak” in the data—may well put the matter to rest once and for all. “Oh, I hope so,” says McGaugh. “I really do hope so.” In the meantime Milgrom holds fast to MOND, although he admits the possibility that his theory will one day be falsified. “As its inventor, I would like it to be a revolution, but I look at it coolly,” he says. “I will be very sad, but not shocked, if [the answer] turns out to be dark matter.”

9. ASTRONOMY

# Deep-Space 'Filament' Shows Cosmic Fabric

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

Astronomers peering back to the early days of the universe have detected the primordial building blocks of galaxies. These cosmological Lego blocks—older and smaller than any detected before—are arranged in an elongated filament. The observations support a popular theory of cosmic evolution in which matter first collected into a network of thin filaments and later coalesced into clusters and superclusters.

The so-called cold dark matter theory was proposed some 20 years ago to explain the structure of the universe. It holds that in the earliest days after the big bang, exotic dark matter, with just a sprinkling of normal matter, clumped into blobs along narrow filaments. Later, these galactic building blocks streamed along filaments into connecting nodes, where clusters and superclusters of galaxies formed. According to astronomer Palle Møller of the European Southern Observatory (ESO) in Garching, Germany, the new observations “lend further strong support” to this picture.

Møller and his team found the primordial filament by making precise measurements of remote blobs of glowing hydrogen gas, using ESO's Very Large Telescope in Chile. The hydrogen clouds are named Lyman-α Emitting Galaxy-Building Objects, or LEGOs, not only for the children's building blocks but also for the radiation the objects emit. Lyman-α radiation is redshifted at very great distances; the redshift is caused by the expansion of the universe and is a measure of distance and look-back time. The newly observed filament has a redshift of just above 3, corresponding to 85% of the current age of the universe. Møller says this is the first convincing observation of a cosmic filament in the very early universe. His team will publish its results later this year in Astronomy & Astrophysics.

The objects that make up the filament are less massive and more representative of the primordial matter in the universe than the larger hydrogen clouds that have been observed previously, says Simon White of the Max Planck Institute for Astrophysics in Garching, a theorist who studies structure formation in the early universe. And because these smaller clouds are much more common, they can be used to trace the large-scale structure of the early universe. “This filament is a first example,” White says. “The network predicted by our simulations may at last be visible.”

10. ASTRONOMY

# The Most Powerful Action Flick Ever

1. Mark Sincell*
1. Mark Sincell is a science writer in Houston.

A neutron star has the lead role in a first-of-its-kind movie. An international team this week released unique footage of Scorpius X-1 gobbling gas from a companion star and then spitting out blobs like so many watermelon seeds. The new flick should help astronomers understand the narrow jets formed by neutron stars and black holes in our galaxy and beyond.

The jets have turned up everywhere in the past decade, from nearby neutron stars to black holes in distant galaxies. Seen up close, the seemingly smooth jets break up into a series of blobs that race down the length of the jet at nearly the speed of light. Astronomers believe that the star or black hole launches the blobs when it vents accumulated hot gas. If they are right, a burst of x-rays from near the star should precede each new blob in the same way a flash of light from a gun barrel signals the approach of a bullet.

But testing the idea is difficult. Blobs cool rapidly and become invisible to x-ray telescopes; it takes many optical and radio telescopes working together around the globe to follow them down the jet. Coordinating such an operation is a logistical and political nightmare that had prevented any team from watching the birth and evolution of a single blob—until now.

For 56 hours in June 1999, Scorpius X-1 was continuously observed by a worldwide network of radio telescopes, called the Very Long Baseline Array (VLBA), and by additional radio telescopes in Australia, China, Japan, and South Africa. Two optical observatories and the orbiting Rossi X-ray Timing Explorer also provided continuous monitoring.

The stellar movie (above)—described in a paper published in the 20 May issue of Astrophysical Journal Letters and viewable at www.aoc.nrao.edu/pr/scox1/scox1.movie.html—reveals the predicted x-ray flash, followed by two pairs of blobs exploding in opposite directions at 95% of the speed of light. After a few hours, the blobs catch up with cooler material left over from previous eruptions. Soon another blob takes off. “This is the first time anyone has ever watched the whole cycle,” says lead author Ed Fomalont, an astronomer at the National Radio Astronomy Observatory in Socorro, New Mexico.

“This is what the VLBA was set up to do, and by combining it with x-ray and optical observations they have pushed it to the max,” says astrophysicist Roger Blandford of the California Institute of Technology in Pasadena. The next step is to figure out what causes the explosions.

11. NUCLEAR PROLIFERATION

# Nuclear Trafficking: 'A Real and Dangerous Threat'

1. Richard Stone

The former Soviet Union's stockpile of fissile material remains dangerously vulnerable, yet the Bush Administration has proposed cutting funds for safeguarding it

STOCKHOLM—At the dusty, windswept Dostyk checkpoint on the border of Kazakhstan and China, it takes several hours to prepare the Soviet-era trains for the continuing journey eastward. Each wagon must be winched up so engineers can replace the undercarriage with one that fits the narrower gauge Chinese rails. As passengers gape at the brute-force procedure, Kazakh border guards sweep the idled train for smuggled goods, sniffing around mainly for opium or other narcotics. On 6 April, they uncovered a potentially more sinister shipment: two satchel-sized lead-coated containers packed with a radioactive substance. Kazakh officials have yet to divulge the results of an investigation to determine whether the contraband is the stuff of nuclear nightmares—highly enriched uranium (HEU) or plutonium that might be fashioned into a bomb—and if so, who the intended recipient was. A U.S. official who requested anonymity believes that the material was bound for North Korea.

The seizure is both a triumph and a warning for the security officers and scientists engaged in a mostly cloak-and-dagger battle to keep the Soviet nuclear genie bottled up. Although the Kazakh police have on several occasions seized nuclear material, including 150 kilograms of uranium fuel pellets smuggled out of the Ulbinsk uranium-fuel processing facility in Ust-Kamenogorsk in 1995, the Dostyk bust was their first at a border crossing. The triumph is that the contraband was detected at all: The remote checkpoint lacked radiation monitors until the U.S. Department of Defense (DOD) paid for equipment for it early last year. The warning is one echoed by similar incidents across Central Asia and Eastern Europe: A decade-long effort to lock down about 600 tons of Soviet-era HEU and plutonium that is considered especially vulnerable—enough raw material for about 40,000 bombs—has far to go.

“We are in a serious situation now—things have deteriorated,” Rolf Ekéus, chair of the Stockholm International Peace Research Institute, said last month at a meeting here on nuclear trafficking sponsored by the International Atomic Energy Agency (IAEA). Indeed, the world is at a critical juncture in its efforts to safeguard nuclear materials. In April, the Bush Administration proposed cutting $100 million from a raft of programs run by the U.S. Department of Energy (DOE) to improve nuclear security in Russia, and the White House National Security Council (NSC) is completing a sweeping review of U.S. defense and nonproliferation policy. A major battle is shaping up in Congress over the fate of these programs, some of which have drawn sharp criticisms in the past few years. “There have to be a number of changes in how we provide assistance,” says Harlan Strauss, director of the DOD's International Counterproliferation Program. Meanwhile, several countries, including Russia, are discussing ways to beef up international efforts to counteract nuclear terrorism. The stakes are enormous. Either “we can spend resources today to eliminate the threat at its source, or we will be forced to spend much more tomorrow to defend ourselves from weapons and technology after they have proliferated,” says Senator Richard Lugar (R-IN), an architect of DOD's much-lauded nonproliferation program; it, too, is under NSC scrutiny. ## A nuclear Silk Road Nuclear trafficking is an insidious consequence of the end of the Cold War. “It has emerged as a real and dangerous threat,” says Anita Nilsson, head of IAEA's Office of Physical Protection and Material Security. At the Stockholm meeting, her agency released new statistics indicating that there have been more than 550 reported incidents of illicit trafficking worldwide since 1993. The majority involve substances that cannot be turned into atomic bombs: for instance, radioactive isotopes for treating cancer, contaminated scrap metal, even gold bars tainted with iodine-131 or U.S. dollars sprayed with zirconium-95. But on at least 16 occasions, police in Europe and Asia have seized HEU or plutonium. The most high-profile incident occurred in 1994, when a German lab traced 363 grams of plutonium powder back to Russia (see sidebar on p. 1634). “That case helped us realize there was a problem,” says Nikolai Kravchenko, chief of nuclear interdiction at Moscow's Sheremetyevo airport. “We had no knowledge, no idea what equipment was needed.” However, it wasn't until April 1996, at the Nuclear Safety Summit in Moscow, that Russia officially acknowledged the threat of nuclear smuggling along its 20,000-kilometer border with 14 countries, says Paula Knepper of Los Alamos National Laboratory in New Mexico. In the wake of that meeting, increased vigilance on the borders and beefed-up security were credited with the fact that no seizures of fissile material were reported to the IAEA between 1996 and 1998. But in late 1998, Russia's Federal Security Service foiled an attempt by insiders to spirit 18.5 kilograms of HEU from a weapons lab in the Ural Mountains, potentially enough for a workable atomic bomb. (It's unclear where the material was headed.) “That's the case I'm most worried about,” says analyst Scott Parrish of the Center for Nonproliferation Studies in Monterey, California. He points out that insider conspiracies, which can defeat even modern security measures, pose a continuing threat. And in the past 2 years, six incidents have been reported, including the April 2000 seizure of nearly a kilogram of HEU in the form of fast reactor fuel pellets in the Republic of Georgia (see map). These incidents are alarming enough, but “we're seeing only a small portion of the problem,” argues Strauss. “We really are on the edge of the unknown.” Russia's nuclear arsenal of about 20,000 strategic and tactical warheads poses some risks, but the warheads are not the main problem, experts say; they are relatively well secured, and their fissile material is hard to remove. The real threat comes from the world's largest stockpile of HEU and plutonium—about 600 metric tons—that's not already incorporated into warheads. This nuclear legacy is stored at weapons labs, civilian research centers, and naval shipyards. As the case in the Urals indicates, much of the material is vulnerable to inside jobs, because many Cold War-era safeguards still in place—guards, guns, and gates—“were designed with spies in mind,” says Alexander Schmid of the United Nations Terrorism Prevention Branch in Vienna. Interpol and domestic intelligence agencies have shared sketchy information about organizations that may be involved in nuclear trafficking and about their motives. Most worrisome are the aspirations of nations that can accrue the expertise necessary to process uranium and plutonium into warheads. Take Iran, for example. Russia has provided assistance and equipment for Iran's nuclear power industry and had cut a deal to sell Iran laser isotope separation technology that could be used to enrich uranium; the deal was scuppered after U.S. objections. “I think this relationship with Iran has been a conduit for all kinds of nuclear material we don't know about,” worries Rensselaer Lee, a senior fellow at the Foreign Policy Research Institute in Philadelphia. “There's an undeniable trend toward proliferation [by] states. If this trend spills over into nonstate actors, we're in real trouble,” says Schmid. The U.S. Central Intelligence Agency has drawn up a list of a dozen terrorist groups known to be attempting to acquire weapons of mass destruction, including Osama bin Laden's Al Qaeda. Whereas some groups hope to develop makeshift warheads, says Roberto Maroto of Interpol's General Secretariat in Lyon, France, intelligence reports suggest that others would settle for “radiological bombs”—conventional devices that could disperse hazardous material over a wide area. “Such devices are easy to make,” he notes. In the early 1990s, the worst hemorrhaging of former Soviet nuclear materials seemed to be into Eastern Europe. Over the past few years, however, concern has shifted to Central Asia and the Caucasus. “This is much more sensible from the traffickers' perspective—lower risks and nearer to potential end users” like bin Laden, says Phil Williams, director of the Matthew B. Ridgway Center for International Security Studies at the University of Pittsburgh. One emerging transit route, says Sergey Chetvergov of Kazakhstan's Atomic Energy Committee, is south from Kazakhstan through Uzbekistan and Turkmenistan into Iran, Afghanistan, and perhaps on to Pakistan. And according to Aysun Yü;cel of the Turkish Atomic Energy Authority, Turkey has become another major route for traffickers. Police investigations of seizures inside Turkey, she says, indicate that material is making its way westward from former Soviet countries—particularly Kazakhstan—over the Caspian Sea, across the Caucasus, and into Turkey, with potential intended destinations being Syria, Iran, and Iraq. “Fortunately, the illicit trafficking incidents involved amateurs” who were not well organized, Yü;cel says. To step up vigilance at the borders, she says, Turkey and the United States last year signed an agreement to install radiation detectors along Turkey's eastern frontier. ## U.S. policy: at a crossroads Since 1993, DOE has spent more than$550 million to safeguard Russia's HEU and plutonium stockpiles. But its Material Protection, Control, and Accounting (MPC&A) program has paid for full security systems for only 86 tons and partial protection for a further 106 tons—in all, about a third of the total that DOE considers most vulnerable. Security measures range from the simple—placing 1-ton concrete blocks over containers holding plutonium at the Mayak Production Association in the Urals—to the complex—using electronic barriers to limit access to sensitive rooms at Moscow region's Obninsk nuclear facility, the origin of 2.7 kilograms of HEU seized in Prague in December 1994. DOE expects it will take another decade and at least $1.7 billion more to deal with the rest, by either securing it or converting it to a form that can't be used for weapons. The Bush budget would cut the MPC&A program from$170 million this year to $139 million in 2002—$87 million less than DOE requested. These cuts would come “just when the program is gathering momentum,” says Russian nuclear expert Matthew Bunn of Harvard University's Belfer Center for Science and International Affairs. He notes that the program has enjoyed consistent bipartisan support, however, and predicts that Congress will restore MPC&A's budget to at least 2001 levels.

The future looks far grimmer for another DOE program, this one designed to help Russia find peaceful work for its nuclear weapons scientists. Russia's atomic energy ministry, Minatom, is downsizing its nuclear weapons complex and has asked DOE for help in creating at least 1500 civilian jobs each year for former weapons scientists in 10 closed, and once top-secret, cities that form the core of this complex (Science, 8 January 1999, p. 160). DOE agreed. In late 1998, it launched the Nuclear Cities Initiative (NCI), with ambitious hopes to spend $600 million over 5 years on projects in all 10 cities. In its first 2 years, however, Congress approved just$22.5 million for projects in three closed cities: two weapons design centers—Sarov and Snezhinsk—and Zheleznogorsk, a production facility. Many of the 370 workers NCI supports work on part-time contracts for the U.S. national labs. NCI won an increase to $26.6 million in 2001, but the Bush Administration has proposed a 75% cut for 2002, to$6.6 million.

The Administration's antipathy toward the program was bolstered by a report released last month by the congressional General Accounting Office. It pointed out that only 30% of NCI funds were spent on projects and activities in Russia; the vast majority was eaten up mainly by travel costs and salaries of U.S. national labs staff members who manage NCI projects and by overhead charges. (DOE officials characterize the expenditures in the U.S. labs as “start-up costs.”) The Russians have not helped NCI's cause, either. Officials in Zheleznogorsk, for example, recently torpedoed a project by refusing to allow technology for a luminescent tube recycling project to be moved outside the city's restricted zone—a fundamental NCI requirement. And on more than two dozen occasions over the past 2 years, the Russian government has denied visa requests from U.S. personnel planning to visit the three NCI-supported cities. These actions have slowed projects and, in a big embarrassment for the program, scotched a U.S.-Russian NCI oversight meeting last November. “They've promised us more cooperation only if NCI spends more money in Russia,” grouses one DOE official.

At the proposed level of funding, “it will be very difficult, if not impossible, to sustain a viable program,” says William Hoehn III, director of the Washington, D.C., office of the Russian-American Nuclear Security Advisory Council, a bilateral think tank. He and other observers hope, however, that a fledgling European initiative can pick up some of the slack. This Italian-led effort, which will focus on environmental and energy-efficiency projects, has just started raising funds from European nations.

The NCI is not the only imperiled part of DOE's year-old long-term Russian nonproliferation initiative. The Administration's proposed cuts would, among other things, eviscerate DOE's efforts to help manage Russia's 30 tons of plutonium extracted for fuel at civilian power plants and shelve research on a geological repository for spent fuel—a Russian version of Yucca Mountain. The cuts would also eliminate an effort to set up an unclassified database of Russia's plutonium stockpile. “The consequences of these cuts are quite substantial,” asserts Bunn. Adds Hoehn, “It sends a signal to me that these efforts are simply not going to be a priority security issue for the Bush Administration.”

View this table:

Some experts argue, however, that the money for programs like MPC&A and NCI would be better spent “disrupting nuclear deals in the making where possible,” as Lee puts it. He advocates stepping up intelligence gathering on so-called rogue nations like Iraq and North Korea and increasing border surveillance, while ending the economic and diplomatic isolation of these states “to undercut the strategic rationale” for developing weapons of mass destruction. Many other experts concur that intelligence operations must be strengthened. “We need to know in more detail what kind of actors are doing what,” says Lars van Dassen, director of the nuclear nonproliferation program at the Swedish Nuclear Power Inspectorate. Others argue that although both kinds of activities are urgently needed, “the best hope is to secure the materials so they are never stolen in the first place,” says Bunn.

## Diplomacy: the missing voice

While the United States debates the future of its nonproliferation efforts, other countries are looking for ways to strengthen international treaties and programs. Experts are now discussing how to tighten accounting under the Convention on the Physical Protection of Nuclear Material, which binds signatories to track exports and imports of weapons-grade uranium and plutonium. The United Nations is weighing new ideas and might consider a Russian antiterrorism measure that would ask states to improve physical controls on all nuclear materials. Another far-reaching scheme is taking shape within IAEA. Physicist Moustafa Bahran, chair of the National Atomic Energy Commission of the Republic of Yemen, is lining up support for a voluntary program to tag and track high-risk materials. He intends to propose it at the next IAEA general conference in September.

Over the next few months, however, the focus will be on the United States. The Administration's defense and nonproliferation policy is expected early this month, and Congress will debate the budget proposals throughout the summer. Provoking the most concern, perhaps, is the apparent rudderlessness of the U.S. nonproliferation strategy. “There's nobody in charge at the moment,” says Bunn. What's needed, he argues, is someone who would report directly to the president and oversee nonproliferation efforts across the government. “I'm absolutely convinced that if the president went to Congress with a plan, we'd see substantial funds for nonproliferation efforts,” Bunn says. Without such a plan and the money to implement it, the cat-and-mouse game between nuclear traffickers and border guards at Dostyk and other remote corners of the world may shift in favor of the smugglers—leaving the world a far riskier place.

12. NUCLEAR PROLIFERATION

# New Effort Puts Radiation Sentinels at the Borders

1. Susan Ladika is a freelance writer in Vienna.

VIENNA—Travelers and luggage passing through customs here at the international airport face more than a collection of surveillance cameras and x-ray machines: For the last several months, they also have been scanned by a neutron and gamma ray detector. So far the focus has been on the detector's performance. But the stakes will go up this summer, when officials begin to search any baggage that triggers the radiation sentinel in an effort to catch nuclear smugglers.

A rise in trafficking of radioactive materials has been one of the most chilling consequences of the breakup of the Soviet Union (see main text). Only recently, however, have European governments begun to crack down on smuggling. A priority is tightening porous borders.

Leading these efforts is the Illicit Trafficking Radiation Detection Assessment Program. Sponsored by the Austrian government and run by scientists from the Austrian Research Centers in Seibersdorf, the program first tested detectors at the Nickelsdorf border crossing between Austria and Hungary. In a 6-month period last year at Nickelsdorf, the detectors revealed a mind- boggling array of radioactive materials crossing the border. Some 13 trucks a day, out of 900 that cross the border, set off the alarms; the rate was lower, but still startling, for passenger vehicles, at one alarm every other day. Border guards discovered everything from contaminated scrap metal to blueberries mysteriously tainted with radioactive cesium. No weapons-grade nuclear materials were intercepted, but such a coup would have been a long shot: “We did not expect to find smugglers,” says the project's manager, Peter Beck, a health physics researcher at theAustrian Research Centers, which heavily promoted the study.

The detectors tested at Nickelsdorf aren't foolproof, however. The devices record collisions between gamma rays and neutrons and sodium iodine or plastic scintillation detectors, producing flashes noted by a photomultiplier and registered by a counter. But such detectors can miss the isotopic signature of smuggled material hidden inside a large shipment of legally transportable isotopes or inside a shielded container, says Rolf Arlt of the International Atomic Energy Agency's Safeguards program. “If several isotopes are present,” he says, “the current generation of isotope identifiers cannot sort them out properly.” Instead, the counters display only the strongest energy peak.

Arlt and other scientists are now testing a new generation of portable detectors, with a cadmium-zinc-tellurium semiconductor that sheds electrons when irradiated by gamma rays or neutrons. These detectors “cannot do miracles,” says Arlt, but their sharper resolution makes them better than the scintillation detectors at distinguishing isotopes.

13. NUCLEAR PROLIFERATION

# Tracing the Shadowy Origins of Nuclear Contraband

1. Susan Ladika is a freelance writer in Vienna.

KARLSRUHE, GERMANY—When German police raided the home of Alfred Jäckle in May 1994, they were looking for counterfeiting material, but they found something far more disturbing: a vial containing a reddish radioactive powder. The police knew whom to call: the European Commission's Institute for Transuranium Elements (ITU) in this city near the French border. Nuclear sleuths at ITU discovered that the powder was red mercury, a Soviet-made plutonium-laced amalgam that analysts believe was designed to reduce the amount of plutonium necessary for a fission reaction. Although police seized only 6 grams of plutonium in Jäckle's home—far too little for a bomb—the incident provided a chilling reminder that the former Soviet nuclear legacy is far from secure (see main text).

Founded in 1963 to investigate the basic properties of plutonium and uranium, ITU has earned a reputation over the past decade as the go-to lab for probing the shadowy origins of seized nuclear materials. Unmasking a substance is the easy part; tracing it back to the source is far more difficult. A team of ITU scientists led by physicist Ian Ray uses cutting-edge techniques to examine how enrichment, irradiation at nuclear power plants, and radioactive decay alter the isotopic composition of nuclear materials.

The most famous case involving the lab occurred in August 1994, when police seized a steel suitcase containing 560 grams of dark-gray, radioactive powder after a Lufthansa flight from Moscow landed at the Munich airport. The arrests of three men—two Spaniards and a Colombian —at the airport as they claimed the illicit baggage ended a successful sting aimed at disrupting an alleged international smuggling ring. ITU scientists were given the task of puzzling out the exact nature of the nuclear material in the suitcase and, more importantly, where it came from. Their investigation revealed that the powder contained 363 grams of plutonium, 87% of which was plutonium-239—weapons-grade material. ITU has confirmed that the seized plutonium originated in Russia but for legal reasons cannot reveal the lab's identity.

So far, ITU has investigated more than 20 cases of suspected smuggling. Most of the work involves routine investigations into incidents of contamination. For instance, in 1997, the lab determined that a radioactive half-meter steel bar found at the Karlsruhe port had been part of a fuel assembly used in a Russian breeder reactor. The high-quality steel was destined for sale at a scrap yard, says Ray.

By German law, ITU has 24 hours to make an initial assessment; detained suspects must be charged within that time or released. The first step involves submitting a specimen to high- resolution gamma spectrometry to measure the energy of the gamma rays it emits. “Gamma radiation is like a fingerprint,” says ITU physicist Herbert Ottmar, with different isotopes emitting rays at distinct energies. Uranium and plutonium, for example, shed low-energy gamma rays. Using this technique, ITU researchers can give a rough indication of whether the material is weapons grade: uranium containing more than 20% of the uranium-235 isotope, or plutonium containing more than 81% of plutonium-239. If the contraband is fuel pellets, their dimensions can point to the source reactor type.

To obtain more precise information about the material's composition, ITU scientists dissolve the material in nitric acid and separate uranium and plutonium from other elements using ion exchange chromatography. Mass spectrometry then reveals their exact isotopic composition.

Within 24 hours, the scientists must draw up a report outlining the elemental and isotopic compositions of the material, state whether it's dangerous to health, and determine whether it's reactor or weapons grade. This is essential information, Ray says, for police to decide whether safety measures must be taken and whether a suspect should be kept in custody.

After this initial flurry of activity, ITU conducts an investigation, which can take up to 2 months, into the nuclear material's origins. This is where the real sleuthing comes into play. Researchers look for trace impurities that are hallmarks of a particular production process or even a specific factory.

A sample's age may yield additional clues. The researchers use a thermal ionization mass spectrometer to compare the amounts of uranium or plutonium with their respective daughter products formed by radioactive decay. Calculations can be tricky: The half-life of plutonium-239, for example, is 20,000 years, and most of the samples are at most a few decades old, so only a minuscule amount of daughter isotopes (in the case of plutonium-239, uranium-234) are present.

Other useful information comes from comparing the abundance of oxygen-18 and oxygen-16 isotopes. When uranium ore is processed, it absorbs water. The ratio of oxygen isotopes in the water varies by latitude and proximity to the ocean, which can help pinpoint the region in which the material was produced. Even dust particles on the packaging can indicate where it has traveled.

All this information is analyzed using a database, developed in cooperation with the Bochvar Institute in Moscow, containing specifications on more than 1000 nuclear fuels produced worldwide for commercial reactors. (The database does not contain information on weapons-grade materials.) Researchers might, for example, feed in data on a uranium pellet, such as diameter, height, degree of enrichment, and concentration of certain impurities. The database would show possible matches, including the type of reactor that the pellet was intended for, the locations of such reactors, and the possible supplier.

Even if scientists can determine where seized uranium or plutonium comes from, it's not necessarily the end of the story. The last legal owner is supposed to take back such materials at its expense. But without access to a company's accounting system, it's tough to prove, and companies aren't usually willing to admit liability, says Lothar Koch, recently retired division head of ITU.

14. LANGUAGE, BRAIN, AND COGNITIVE DEVELOPMENT MEETING

# What Makes the Mind Dance and Count

1. Michael Balter

PARIS—Four dozen leading cognitive neuroscientists met here at the Collège de France from 3 to 5 May to share their latest data on topics such as amusia—an inability to perceive music—and number sense in infants. The “Language, Brain, and Cognitive Development” gathering was held in honor of Jacques Mehler, founder of the journal Cognition, who will soon retire from?.

## Wired for Sound, Not Music

Che Guevara was widely recognized as a man of many talents. Yet one talent the 1960s revolutionary lacked was the ability to hear music, a shortcoming he was acutely aware of. According to one account, Guevara was at a party one evening when he spotted a nurse he wanted to dance with. He asked a friend to give him a nudge when the orchestra struck up a tango. But the friend got the signal mixed up, sending Guevara out on the dance floor to dip and swirl his partner absurdly to the tune of a soft Brazilian samba.

Guevara suffered from congenital amusia, a nearly total tone deafness that turns music into mere noise. Although 5% or more of some populations suffer from this syndrome, it has not been widely studied. At the meeting, Isabelle Peretz of the University of Montreal reported preliminary results with amusical subjects that may support the hypothesis that the brain contains specific neural pathways for music.

Peretz studied 11 amusical adults who had a high level of education, didn't have any loss of hearing or other obvious neurological impairments, and had tried to take music lessons when children and thus had been exposed to music from an early age. These individuals, along with 67 control subjects, were given a battery of tests for musical ability and other cognitive skills, such as language ability. Most members of the amusical cohort were unable to detect when a tune, such as “Happy Birthday,” was played with pitch alterations that made it clunk in the ears of the control subjects. One typical case, Peretz says, was that of “Monica,” whose IQ measured 111 and who was working on a master's in health sciences. Despite functioning normally in all other areas of mental life, Monica could neither recognize nor sing familiar tunes such as “Frère Jacques,” even though as a native of French-speaking Quebec she had been exposed to the song since infancy. The only nonmusical impairment that Peretz and her Montreal co-workers were able to identify was a decreased ability of some subjects to detect prosody, or pitch variations, in normal speech.

Thus, aside from impairing their singing and dancing skills, amusia may have seeped into some subjects' language abilities as well. Peter Jusczyk of Johns Hopkins University in Baltimore and others caution that this prosody deficit might complicate a neat picture by indicating a neural linkage between music and language pathways. “I would like to see better evidence that amusia can be fully disentangled from prosody in language,” says Jusczyk. “Prosody, after all, refers to the musical aspect of language.”

Despite the spillover between pure music comprehension and sensitivity to the subtle music within speech, Peretz concludes that her results and those from other studies are consistent with the idea that “there must be specialized neural systems for music,” which amusical people lack from birth. Indeed, the notion that musical ability is hardwired into the brain has recently received support from studies of identical twins (Science, 9 March, pp. 1879 and 1969). Also bolstering this conclusion, Peretz says, are studies of brain-damaged patients who have lost their musical abilities, as well as studies of people with “musicogenic epilepsy,” a rare condition in which seizures are triggered by music. Peretz says her team will now turn to techniques such as magnetic resonance imaging to try to pin down exactly where in the brain these neural circuits are located.

Peretz's study is receiving high marks. “There is a very strong case for specific neural pathways,” says Uta Frith of University College London. But the findings beg the question of what adaptive purpose such hardwiring might serve. In several recent articles, Peretz has argued that the ability to hear music is an adaptation possibly designed to increase social cohesion among groups by providing them something to share. But some of her colleagues are skeptical. “She has provided compelling evidence that there are [neural] pathways for music,” says Steven Pinker of the Massachusetts Institute of Technology in Cambridge. “But whether they were selected in the course of human evolution as opposed to being a byproduct of … pathways that evolved for other purposes is still an open question.”

## Born to Enumerate?

Albert Einstein, describing how he arrived at such highly mathematical concepts as the theory of relativity, once wrote: “Words and language … do not seem to play any part in my thought processes.” For some cognitive scientists, such perceptions support the notion that our brains are equipped with a built-in “number sense,” independent of language or other symbolic functions. At the meeting, Stanislas Dehaene of the French Atomic Energy Commission's neuroimaging lab in the Paris suburb of Orsay presented new evidence for this hypothesis from studies of infants.

Dehaene has long argued that our ability to perform calculations is rooted in two distinct brain regions. Exact arithmetic, he claims, is a cultural invention requiring number symbols—such as 1, 2, 3—and these calculations are carried out in left-hemisphere circuits also used for language. But approximate arithmetic, corresponding to a general number sense that has evolved in humans and some animals, is independent of language and can be mapped to parietal lobe circuits (Science, 7 May 1999, pp. 928 and 970). Dehaene has found support for this arithmetic duality in research he and other neuroscientists have conducted that demonstrates that babies, monkeys, and even rodents can distinguish numbers. Additional evidence comes from brain-damaged patients who have lost their ability to do arithmetic.

The new studies, which Dehaene carried out in collaboration with Ghislaine Dehaene-Lambertz of the French national research agency CNRS in Paris, investigated alterations in electrical activity in the brains of 4-month-old babies exposed to changes in number patterns. The babies' heads were covered with a light mesh made up of 64 electrodes. In the first stage of the experiments, the researchers presented numbers to the babies as tones, flashes of light, or spoken syllables. For example, the number 2 could be represented by two tones in quick succession. The electrodes recorded the resulting event-related potentials (ERPs) in the babies' brains.

In previous work on the ability of babies to distinguish spoken syllables, the pair had found that one ERP peak increased significantly whenever a novel syllable was heard. In the new studies of number sense, they found a similar effect. A peak that arose about 750 milliseconds after the stimulus decreased in intensity if the baby was repeatedly exposed, or habituated, to the same number—for example, the tones beep-beep, beep-beep, beep-beep. But if the last in the series of numbers was changed —such as beep-beep, beep-beep, beep-beep-beep—this peak shot back up to its prehabituation level. The effect was independent of the stimuli (tones, flashes, or spoken sounds), even if the stimuli were mixed in the same experiment—indicating, Dehaene said, that the babies were responding directly to changes in number.

Dehaene and others at the meeting interpret these results as further support for the idea that humans possess an intrinsic number sense long before they can speak or perform calculations. “These studies are wonderful,” says Elizabeth Spelke of the Massachusetts Institute of Technology. “They fit in beautifully with the ensemble of evidence … that there is a [brain] domain-specific, dedicated system for processing approximate [numbers].”

Such findings may help provide clues to the evolutionary origin of number sense. Dehaene's study “parallels very nicely the work on animals,” says Marc Hauser of Harvard University, who presented similar results at the meeting from experiments on cotton-top tamarin monkeys. And Spelke praises the use of ERP measurements as a step forward in the study of how cognitive processes in babies develop, work that in the past has relied heavily on behavioral indicators such as how long an infant spends gazing at a stimulus: “This is better data than from virtually any of our behavioral methods to study infants.”

15. INFECTIOUS DISEASES

# Is the U.S. Doing Enough to Prevent Mad Cow Disease?

1. Martin Enserink

U.S. officials say they're taking every reasonable step to keep mad cow disease out. But critics still see chinks in the country's armor

On a cold spring morning, when the hills in East Warren, Vermont, were covered with a fresh pack of snow, the Faillace family lost its livelihood. It happened in a government action that—if you hear Larry Faillace recount it—was every bit as dramatic as the one that wrenched Elián González from his Miami relatives last year. At 5:30 a.m. on 23 March, says Faillace, armed federal agents in flak jackets entered the family farm and ordered his three children to stop feeding the sheep. Shortly after, an enormous truck pulled up, and U.S. Department of Agriculture (USDA) agents began loading all of the Faillaces' 126 sheep. A few hours later, the truck was gone, leaving the family, the town, and several dozen protesters behind in anger and shock.

The early morning raid is perhaps the most dramatic example of the U.S. government's efforts to keep “mad cow disease,” or bovine spongiform encephalopathy (BSE), out of the country. USDA suspected that the sheep, which the Faillaces had imported from Belgium and the Netherlands in 1996, were infected with a sheep version of BSE. So they took no chances: The entire herd was destroyed days after the animals were seized.

To prevent a BSE outbreak, USDA, the Food and Drug Administration (FDA), the U.S. Customs Service, and other government agencies have put in place a long list of safeguards—from barricading the borders to analyzing brains of people suspected of having died from the human form of mad cow disease, called variant Creutzfeldt-Jakob disease (vCJD). Yet public interest groups and others have long argued that the government's response has been too little, too late. Because of this lax response, the critics say, the disease may well be among us. And if it is, the government is not vigilant enough to detect it, they warn, nor tough enough on the meat industry to keep it out of the human food chain.

Government agencies say they've taken “aggressive” measures to prevent the disease, and many scientists agree. They admit that the precautions are not failsafe and that the disease could emerge in the country—but say the risk is vanishingly small. Even so, the concerns are reverberating on Capitol Hill, where House and Senate committees have summoned officials to discuss the risks. Senator Richard Durbin (D-IL) announced recently that he will introduce a bill that would beef up border inspections and other controls to keep BSE out of the food chain.

But underlying the argument is a broader question: How much prevention is enough? Scientists point out that the U.S. defense against BSE consists of multiple tiers, each of which would have to break down for an outbreak to occur. Although the risk could be reduced further, the necessary control measures would become increasingly costly and draconian. “You don't go spending half the budget to reduce the risk to zero,” says Paul Brown, a senior scientist at the National Institute of Neurological Disorders and Stroke (NINDS) in Bethesda, Maryland, “especially in view of much more serious public health problems that afflict us.”

## Multitiered containment

BSE is one of the so-called transmissible spongiform encephalopathies (TSEs), a mysterious class of fatal brain diseases. Scientists are still debating their etiology, but the leading theory is that they're caused by abnormal forms of proteins, called prions. Several TSEs have the scary ability to jump the species barrier; in Britain, for instance, 99 people are known to have died or are presumed to be dying of vCJD, most likely contracted after eating meat products from infected cattle. Epidemiologists expect more cases in the United Kingdom, but they're not sure how many; there could be tens of thousands.

In the United States, the first line of defense is to block entry of the BSE agent, and most people agree that the government has been thorough. As early as 1989, USDA banned the importation of all ruminants (cattle, goats, and sheep) and many animal products from the United Kingdom and other countries with BSE. In 1997, when BSE cases started showing up in several other countries, that ban was extended to all of Europe. The 500 or so animals that were imported from those countries before 1997—such as the Vermont sheep—have almost all been quarantined or purchased and killed.

But closed borders offer no guarantees. Researchers still don't know how BSE arose in Britain, but whatever the process, it could happen here, too. One prominent theory is that the agent that causes scrapie, a TSE in sheep, crossed the species barrier and ignited the cattle epidemic in Britain—specifically, when cattle were fed meal that contained infected sheep tissue. That practice is now banned in the United States, making such a scenario unlikely.

But BSE could also arise out of nowhere. Each year about one in every million humans worldwide gets CJD spontaneously, and it's possible that the same happens in cattle—or indeed all mammals. Last year a U.K. panel chaired by Lord Andrew Phillips supported the theory that such a “sporadic” case may have started the British outbreak.

Work by Richard Marsh, a veterinary virologist at the University of Wisconsin, Madison, who died in 1997, suggests that sporadic cases of a cattle TSE may have already arisen in the United States. Five times between 1947 and 1985, a disease called transmissible mink encephalopathy decimated populations on U.S. mink farms. After investigating the last outbreak, Marsh concluded that cow carcasses fed to the mink were the most likely source of the disease agent. He speculated that at least one of the cows must have had a TSE.

Another potential source of BSE is a homegrown prion disease that afflicts deer and elk. Conceivably, this ailment, called chronic wasting disease, could jump to cattle or sicken people who eat infected venison (see sidebar).

But would anybody have noticed if the United States had a couple of cases of BSE? Probably not, say some critics. USDA now tests some 50 suspect cows a week. The test program pales in comparison to the massive effort started last year in the European Union, where every cow over 30 months old is tested after slaughtering. The United States should do something similar, says Thomas Pringle, a molecular biologist with the Sperling Biomedical Foundation in Eugene, Oregon, who maintains a Web site about BSE. “You can try all these containment measures, but at the end of the day the question is: How much BSE do you have?” he says. “The way to find out is to run hundreds of thousands of tests.”

Testing at that level would be silly, replies Linda Detwiler, a senior staff veterinarian at the USDA, because BSE has never been found in the country. Even so, she says, this year the agency will double the number of tests it performs.

## Cows eating cows

Even if a cow got BSE and it went undetected, that wouldn't spell doom for the rest of the nation's livestock. The only plausible way for an outbreak to occur would be if that cow were fed to other cows, thereby passing on the infectious agent. For decades, cows did eat other cows, when they were fed meat-and-bone meal, a protein concoction produced by milling and boiling (or “rendering”) the carcasses of, say, sick farm animals, road kill, and dead pets. The epidemic in Britain is believed to have been fueled after infected cattle were recycled on a large scale.

But this route is now cut off in the United States, at least in theory: FDA banned feeding most mammalian protein to all ruminants in 1997. Those same proteins can still be fed to pigs and poultry, however, so FDA has ordered rendering plants and feed mills to prevent commingling of the two types of feed. Enforcing this separation has proven difficult, however. A March 2001 FDA inspection report showed that about one in seven feed mills and rendering plants didn't have adequate procedures to prevent commingling; many haven't been inspected yet.

Indeed, Purina Mills in Texas discovered in January that a new employee had mistakenly let cattle protein slip into a batch of cow feed. After 1222 animals that had been given the suspect feed were quarantined, Purina paid for the entire herd to be destroyed. “Who knows how many other cases have been swept under the rug?” asks Peter Lurie, a researcher at Public Citizen, a consumer watchdog group in Washington, D.C., and a member of FDA's advisory committee on TSEs. Lurie would like to see the FDA get much tougher on the feed industry.

Although that may not be a bad idea, others say, the current situation is hardly a recipe for disaster. Suppose a BSE-infected animal did end up in cattle feed, says NINDS's Brown, and a few cows became infected and went to the slaughterhouse undiagnosed. For the outbreak to continue, they would have to be rendered themselves and mistakenly turned into cattle feed again. “A regulatory breakdown of this magnitude is virtually impossible,” Brown wrote recently in Emerging Infectious Diseases. Similarly, Will Hueston, a veterinary epidemiologist at the University of Maryland, College Park, says the risk of even a single case of BSE is “pretty darn small.”

The chance that humans might get vCJD from eating infected cattle is even smaller. But here, too, critics see loopholes that they would like closed. European countries now require brains and spinal cords to be removed from a carcass directly after slaughter; no such safeguard exists in the United States.

Another route of infection could come from the local health food store. In 1994, Congress deregulated dietary supplements. Many of these contain animal parts— including brain tissue. Although the FDA has asked manufacturers not to use such materials from countries known to have BSE, it can't ensure that no cow brains make it in, says Lurie. Supplements are a problem as long as FDA lacks jurisdiction over them, agrees Brown, who chaired FDA's advisory panel on TSEs until last January.

View this table:

## How much is enough?

In the end, nobody disputes that more can be done to prevent BSE; the question is how much the country is willing to invest. For instance, banning the use of all animal proteins in livestock feed would all but eliminate any risk, says Brown. But it would be the end of the \$2.5 billion rendering industry, and it might make meat more expensive, he says.

In his recent commentary, Brown summed up seven holes in the safety net that critics are sure to pounce on if a BSE case were ever to occur. Even so, Brown thinks the current safeguards earn “high marks.” Rather than closing each and every hole, he suggests that the money could be better spent on other public health issues, such as diabetes, hypertension, or car accidents.

George Gray, a risk analyst at Harvard School of Public Health in Boston, agrees. “Every bit of attention and effort we put into [BSE] takes away from something else,” says Gray. “And I think there are considerably bigger risks out there in the food supply.” An estimated 5000 people a year die from microbial contamination in food alone—many more than would be harmed by BSE in any plausible scenario, he asserts. At USDA's request, Gray is studying the risks of BSE and related diseases in the United States. The study, which will guide future policy, will be presented to the agency within the next 2 months.

Lurie dismisses such comparisons. “By that argument, we should not worry about microbial contamination because many more people die from cancer,” he says. Although the risk may be low, he says, the worst-case scenario would have such disastrous public health and economic consequences that extreme caution is warranted.

That's the argument that led USDA to kill the Faillaces' sheep and another nearby flock, says Detwiler. Tests carried out last year on four slaughtered animals showed signs of a BSE-like disease, although it wasn't clear whether it was scrapie or a sheep version of BSE. Sheep have been infected with BSE in the lab, but no natural cases have been found in the world. If the Vermont sheep did have a form of BSE, they would be the first. Better to err on the side of caution, says Detwiler, than for the United States to have that dubious honor.

The Faillaces, who fought the seizure in a long legal battle, claim the sheep were healthy and the tests were sloppy. Additional tests of the Faillaces' sheep are now being performed at the National Animal Disease center in Ames, Iowa. The results, says Detwiler, will be available in a few months—about the time that Gray's risk assessment is due.

16. INFECTIOUS DISEASES

# America's Own Prion Disease?

1. Martin Enserink

Hunting just isn't what it used to be—at least not in certain parts of Colorado and Wyoming. Not only do hunters have to wear orange jackets to avoid being shot; some scientists now worry that their trophy animals may kill them.

Since the 1960s, deer and elk in these states have been known to suffer from a chronic wasting disease (CWD), a fatal condition whose first symptoms are emaciation and abnormal behavior. In the 1970s, CWD was discovered to belong to the so-called transmissible spongiform encephalopathies, like scrapie in sheep and Creutzfeldt-Jakob disease (CJD) in humans. But hunters and others gave it little thought until 1996, when Britain concluded that a similar disease affecting cattle, bovine spongiform encephalopathy (BSE), could cause a new and fatal form of CJD in humans, vCJD. If eating beef can give you vCJD, then what about venison. So far, there's no good answer.

CWD, which affects white-tailed deer, mule deer, and elk, was first diagnosed in captive deer in research centers, although scientists don't know if it originated there. Today, it occurs in the wild throughout northern Colorado and southeastern Wyoming; two cases have been found just across the border in Nebraska and one in the Canadian province of Saskatchewan. It has also hit elk farms in several U.S. states and in Saskatchewan. Unlike BSE, CWD doesn't seem to be food-borne; instead, it's probably transmitted through saliva or feces, says Elizabeth Williams, who studies the disease at the University of Wyoming in Laramie. Williams estimates that 4% to 6% of mule deer and less than 1% of free-ranging elk in the endemic areas are infected. So far, CWD hasn't been found elsewhere in the world—but then, few countries have been looking.

One reason Williams and other researchers worry about CWD is that it might trigger a new animal disease. For instance, cattle in the endemic areas could pick it up and develop a new strain of BSE. Three years ago, Williams and colleagues at the Colorado Division of Wildlife and the National Animal Disease Center in Ames, Iowa, started experiments to determine the likelihood of that scenario by exposing cattle to CWD. The first results, although not clear-cut, are worrisome. The team injected brain tissue from infected deer into the brains of 13 cows. Last January they reported that three of the 13 had become sick with a disease resembling BSE and had to be killed. Admittedly, injecting material into the brain is an unnatural way to induce an infection, so perhaps infection doesn't occur outside the lab, says Williams. So far, cattle that were fed infected brains or were housed with infected deer are still healthy, she notes. The researchers plan to monitor the animals for at least another 7 years.

The direct risk to humans from eating meat from infected deer or elk is equally puzzling. Recently, researchers at the Centers for Disease Control and Prevention (CDC) in Atlanta have taken a close look at three people who died from CJD and had a history of eating venison. One, a woman whose father used to hunt in Maine, ate the meat when she was a young child; the other two were hunters from Utah and Oklahoma—where CWD has never been found—who frequently dined on venison. A worrying common denominator is that all three were under 30, says CDC epidemiologist Ermias Belay. Such cases are “extremely rare,” he says; most CJD victims are over 55. In Britain, however, vCJD strikes people at an average age of 29.

Although suggestive, this small sample is a long way from proving a link between CWD and CJD, says Belay. For one, vCJD patients all share a typical brain pathology that sets them apart from classic CJD patients. The brains of the three venison eaters, however, suggested classic forms of CJD, says Pierluigi Gambetti of the National Prion Disease Pathology Center in Cleveland, Ohio, who studied their brains. Furthermore, the three each had different subtypes of the disease. But most important, when Belay interviewed their relatives and physicians, he couldn't find hard evidence that they ever ate meat from any of the endemic areas.

Still, Belay says he can't exclude the link either—and that's why CDC plans to keep tabs on future cases of CJD. In the meantime, health officials in Colorado and Wyoming are advising hunters not to shoot or handle sick-looking deer and to avoid eating brain, spinal cord, and other possibly infected tissues.

Even the next best thing to eating your own prey—taking the head home as a trophy—might be risky, says molecular biologist Thomas Pringle of the Sperling Biomedical Foundation in Eugene, Oregon. To sever a head, hunters have to cut right through the spinal cord. “It's potential biosafety level 3 material,” says Pringle. “I'm not sure Joe Sixpack should be throwing that in the back of his pickup truck.”