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NS 12 oct 02
Official report falls to quell safety fears over Colombian anti-drug campaign
A PR0GRAMME designed to destroy Colombia's huge illegal drugs business could be poisoning farmers and damaging the environment, critics in the US claimed last week. Backed by $1.3 billion cvf US government funds, drug enforcers routinely identify fields of coca plants and opium poppies, and spray them ftm the air with herbicide. Around 120,000 hectares have been sprayed with the herbicide glyphosphate. But although glyphosphate is considered to be relatively safe for humans and the environment, the Colombian govemmerrt has received over a thousand complaints from people who claim to have suffered ill effects after coming into contact with the chemical. Reported symptoms range ftm skin and eye irritations to coughing and vomiting. Some critics suspect additim to the spray are responsible. Others on the ground complained the spray had killed fbod crops when it drifted onto them ftm nearby fields. The US Congress asked the State Departmerrt to assess whether aerial spraying could harm lepi crops, people or the environment. hs report to Congress last month concluded the programme had no adverse affects. But scientists who have seen the report now say the assurances are worthless. Jim Oldham of the Institute fbr Science and Interdisciplinary Studies, a non-profit arganisation focusing on science in societjf, based in Amhemt, Massachusetts, says the report failed to investigate whether sprayed areas had more health problems than those Mat are ncrt sprayed. Also, the US Environmental Protection Agency ran computer models showing the herbicide could ddft into neighbouring fields and kill as much untargeted vegetation as drug crops. The official report suggested this was not a problem. A State Department spokeswoman defended the anti-drugs progmmme, saying ltispecdons are carried out to ensure that the spraying is not causing harm. Kurt Kleiner
Wannabe fathers generate more testosterone for those special nights
FOR men, simply wanting to have a child could be enough to help it happen. It seems wannabe fathers adjust their testostemne levels to make conceprtion more likely. Katharina Hirschenhauser, an expert in sex hormones, and her team at the Institute of Applied Psychology in Lisbon set out to see if there was arry link between men's testosterone levels and their sexual behaviour. They asked 77 volunteers to measure the testostemne in their saliva every morning for 90 days. Over the same period, the men also recorded their sex lives in intimate detail, documenting the "Intensity" cyf each encounter, whether with their regular partner or not. All the men had dhterent patterns of testosterone peaks and tmughs overthe period. But in men trying fbr a baby, peaks in testostemne levels coincided far more often with periods of intense sexual activity (Hormones and Behavior, vol 42, p 172).
Hirschenhauser says the finding shows men can subconsciously influence their hormone levels. "Males can be responsive to their partners, but only if theywant to be,"shesays. Jim Pfaus, an expert in sexual neurobiology at Concordia University in Montreal, says this could overturn a common and uncharitable belief about men. "We tend to think (yf the little brain being disconnected from the big brain," he says. Coordinating sexual activity with peaks in testosterone makes sense fbr men who want to be fathers. Rises in testosterone also trigger a hormonal pathway that increases sperm production, making conception more likely. "in short, you're less like" shoot blanks," says Pfaus. There may be more to it than wannabe fathers simply having more sex when theirtestosterone is high, adds Pfaus. ft is well known that women are more receptive to sex around the time of ovulation. Previous studies have also shown that women who live together synchronise their periods - probably through pheromonal cues. Perhaps, says Pfaus, men who want a baby respond directly to their partner's pheromones and synchronise their testosterone peaks with the mid point cvf their partner's cycle, when they are most likely to conceive. James Randerson
Climate modellers overlook crucial factor in warming
DANNY PENMAN GLOBAL warming predictions could be wildly inaccurate because climate models fail to take changes in land use into account. Turning more land over to farming, introducing irrigation and reforestation could have a greater effect on global warming than changes in industrial carbon dioxide emissions, says Roger Pielke, an atmospheric scientist at Colorado State University. Pielke's team reached their conclusion after modifying a standard climate change model to take account of changes in land use since the beginning of the 18th century. Among the factors they included were estimated changes in forest sizes, areas of farmland and irrigated land. When they ran the modified model, they found that these changes had a significant influence on the climate over the past 300 years. They raised midwinter temperatures in westem Europe by about 3 'C, and speeded up the rapid jet streams high above the Atlantic and Pacific by about 6 metres per second. The model shows forests help to cool the atmosphere as water evaporating from leaves absorbs heat. Turning forest into farmland removes this cooling effect, although irrigation made the temperature rise less severe. Climate experts will need to rethink how they model climate change, says Pielke. "The human influence on climate is more complex and diverse than we have appreciated. We are going to have to start thinking more holistically," he says. Pielke also found that certain proposals in the Kyoto Protocol to reduce global warming could actually have the opposite effect. For example, planting forests to absorb carbon dioxide can actually lead to warming if they are planted where snow falls, because the land will then reflect less sunlight. Richard Betts, a climate expert at the Hadley Centre for Climate Prediction and Research in Bracknell, Berkshire, says Pielke's findings should be taken seriously. "This work suggests that there are shortcomings in the protocol that have to be addressed," he says.
Massive balancing act pins down big G
BY SLOSHING around 13 tonnes of mercury, scientists have made the most accurate measurement yet of Newton's gravitational constant G. The result adds weight to a controversial theory that the strength of gravity is subtly affected by the Earth's magnetic field. The size of G determines the strength of the gravitational pull that bodies exert on each other. But physicists have only a rough idea of its value. The two most accurate measurements of G so far, taken by teams at the University of Washington in Seattle and at the International Bureau of Weights and Measures near Paris, have experimental errors of about ioo parts per million, yet their values differ by lo times that amount. Some researchers believe that this difference could be due not to the experiments, but to the Earth's magnetic field, which varies in strength at different locations (New ScientiSt, 21 September 2002, P 14). Both the Paris and the Seattle experiments were based on the original method used by Henry Cavendish in 1798, which uses a torsion balance to measure how much the gravitational pull of a known mass twists a dumb-bell- shaped weight supported by a thread. Because torsion balances can only support a tiny weight, the gravitational force is correspondingly small, and hard to measure accurately. Now a team of physicists from the University of Zurich has come up with a more direct approach, which allows them to measure G with an accuracy of just 33 parts per million. In a concrete pit near Villigen, Switzerland, the team used a sensitive laboratory balance to measure the difference in weight of two small masses, while placing two huge tanks of mercury either above or below them (see Graphic). By measuring how the mercury's gravitational pull affected the weights of the test masses, the researchers were able to calculate a value for G. Their answer, 6.67404 x 10-11 ml/kg/sec' agrees with the Seattle value, but not with the Paris result. Stephan Schlamminger, leader of the Zurich team, thinks this disproves the Paris result: "It is very unlikely for both results to be valid." But jean-Paul Mbelek of the French Atomic Energy Commission near Paris is not so sure. He claims that if theories suggesting a link between gravity and electromagnetism are correct, then the Earth's magnetic field could noticeably affect gravity, meaning G should be larger near the poles where the magnetic field is stronger than it is at the equator. He calculates that the magnetic field in Seattle should be about the same as at Villigen, while Paris is slightly further north. Taking that into account, says Mbelek, the Villigen result matches his best prediction.
Hard evidence left by biggest killer of all time points to death by suffocation
AIR-STARVED soil could have been a key player in the largest exdncdon everts strike Earth. The claim follows the discovery of a rare mineral in ancient soil collected from Antarctica. The extinction, at the end of the Permian pedod 250 million years ago, wiped outvirtually all madne life and some 70 per cent crf land animals. But the reason for the extinction, which preceded the rise cyf the dinosaurs, has been a long-standing puzzle.
Now Greg Retallack and his team of geologists at the University of Oregon think they have found what could be a major factor in the extinction. Retallack collected fbssillsed soil samples that formed in Antamtica just after the Permian period ended. The soil contained nodule-shaped minerals that Retallack's student, Nathan Sheldon, identified as berthierine. This imn-rich mineral forms only in environments where oxygen is scarce. If the oxygen levels in the soil were low enough to allow berthierine to form, the soil would not have been able to support plant life, says Retallack (6eology, vol 30, p 919). "You've gat intolerably low levels of oxygen," he says. "it would be enough to kill [the plants] off completely." A drop in oxygen in the soil backs up a leading theory that a key factor in the mass extinction was a huge release of methane gas ftm ftzen sheets of methane and water, called methane hydrate, found mainly under seabeds. Once released, clouds of methane would quickly cut oxygen levels in the atmosphere and soil by converting it into carbon diodde. The collapse cyf plarit life would soon have caused large numbers crf animals to starve. Methane bubbling up ftm seabeds into the air above could also have depleted the oxygen in the water, killing off marine life. Scientists still aren't sure what could have triggered such a huge methane release, though. An asteroid strike could have released the gas by breaking up sheets of methane hydrate, but there is no evidence of an impact at that time. Other possibilities are massive volcanic eruptions, or climate change that thawed the icy methane. Jeff Hecht
SUPPOSE you had a little gadget that could explain all the greatest mysteries of the Universe. Like the scientific equivalent of some ancient oracle, you could consult it to learn how the laws of physics emerged in the fireball of the big bang. Press the right buttons and it would tell you why the cosmos is ballooning outwards ever faster, and why matter, rather than its nemesis antimatter, dominates the Universe. The gadget has already been invented. It doesn't look like much: a blob of helium chilled almost to absolute zero. But according to Grigori Volovik of Helsinki University of Technology and the Landau Institute for Theoretical Physics in Moscow, this refrigerated droplet can help explain some of the Universe's most elusive secrets. It can lay bare the nature of gravity and the intimate workings of black holes, for example. It exposes the newborn Universe to scrutiny and tracks down the origin of physical laws and elementary particles. And the helium oracle has already pronounced on the major quest in physics, the search for a quantum theory of gravity. "it doesn't exist," Volovik says. His ideas are controversial, of course, and intensely complex. But they are winning some prominent supporters, and Volovik's following could be about to grow. In a book due to be published next year, Volovik has spelled out exactly why helium is the oracle every cosmologist should be consulting. His conviction arises from three decades of work with superfluid helium-3, a weird liquid that defies common sense. When helium is cooled to near absolute zero, it stays liquid but starts to follow quantum rather than classical rules. Effectively, the atoms lose their individuality and begin to influence each others'movements. Helium-3 can then perform tricks like flowing along pipes without friction and defying gravity by climbing the walls of a beaker. We have long known that superfluid helium has profound mathematical links with the cosmos. For a start, as with every other moving fluid, the way sound moves through superfluid helium is mathematically similar to the way light moves in a gravitational field. But, with helium, the parallels run much deeper. The first indication of helium's peculiar aptitude for cosmology came with its mimicry of "cosmic strings". Most scientists believe that in the very first moments of the Universe, there was only one force. Within a split second, this force decayed into the four very different forces we know today: gravity, the strong and weak nuclear forces, and the electromagnetic force. In the 1970s, Tom Kibble of Imperial College, London, suggested this process would thread the cosmos with stringy flaws or "defects": long, thin cracks - or cosmic strings - in the fabric of the expanding Universe. The idea was appealing because matter could have clustered around the strings to form galaxies, explaining why the galaxies we see today lie along filaments separated by giant voids. it was hard to see how this idea could be tested until, 15 years later, Wojciech Zurek of the Los Alamos National Laboratory in New Mexico noticed that the maths underpinning cosmic strings is the same as the maths describing similar kinds of defects in superfluid helium. As liquid helium cools into the superfluid state, it undergoes a phase transition, akin to water turning into ice. This can leave behind little flaws. When different parts of the fluid choose to move in different directions, lines of rotating vortices are created along the border where these regions meet. Zurek made clear predictions about what scientists could expect to see in experiments that generate vortices in superfluid helium by spinning it in a rotating cryostat (New Scientist, 21 September 1996, P 46). If Kibble's idea about cosmic strings was right, there should be an obvious relationship between the smallest vortices that can expand and be detected, and the chamber's rotation speed. Volovik and his colleagues at Helsinki University's Low Temperature Laboratory decided to put the theory to the test in 1995. And sure enough, the numbers matched up. "We checked that Kibble was right - his scenario does work," says Volovik. In the past couple of years, measurements of the cosmic microwave background - radiation left over from the big bang - have indicated that cosmic strings may not have played such an important role in shaping the distribution of galaxies. Nevertheless, confirming that such defects may have formed was a major triumph for helium cosmology, proving its predictive power. So Volovik has now set his sights on bigger things. indeed, he's looking for the holy grail of physics. The phenomena that excite physicists most occur at high energies and on the tiniest scales. These are the conditions of the Universe's birth. Yet our theories simply don't work at these scales, and our particle accelerators aren't powerful enough to achieve the highest energies. But while the real Universe guards its secrets, the helium universe tells all. Volovik's oracle is a superfluid state of the helium-3 isotope called 3He-A. Superfluid helium-3 can exist in two phases, A and B, depending on its temperature and pressure. Volovik claims the A phase accurately mimics almost all the properties of space-time, which is the four-dimensional fabric of the Universe. Far from being nothing, the vacuum of empty space is a frothing sea of virtual particles that pop in and out of existence by briefly borrowing energy from the vacuum. 3He-A is just as complicated. It will never solidify, even if you could chill it to the unattainable zero kelvin. And at a whisker above absolute zero, "quasiparticles", packets of sound energy, start to appear. The slight sloshing of atoms at anything above zero kelvin generates little sound waves and - like all kinds of waves - these consist of packets of energy of various sizes. The quasiparticles can be detected and, what's more, their behaviour follows some of the same mathematical laws that govern the behaviour of elementary particles in a vacuum, such as electrons, neutrinos and quarks. For instance, some quasiparticles interact with each other in the same way that gravitons, the hypothetical carriers of the gravitational force, interact with matter particles such as the electron, according to Volovik. In fact, he says, 3He-A, like space-time, can reveal all the physics of both gravitational and electromagnetic fields. His analysis Of 3He-A has led him to some startling conclusions. First of all, he says, helium indicates that gravity is not a fundamental property of the Universe. In other words, it wasn't there from the beginning. As the helium liquid cools from a high-energy, chaotic state into the low-energy, superfluid state, order begins to take shape. First the quantised state emerges. Only then do quasiparticles showing specific properties - the analogues of gravity and electromagnetism, for instance - start to appear. He believes this shows the newborn cosmos was born in a lawless state. In the real Universe, everything was superhot and full of energy at first. Then, as the big bang fireball cooled, a single force that briefly ruled the Universe emerged after about 10-41 seconds, according to Volovik. Sometime after that the forces we know today - gravity, the strong nuclear force and so on - budded off. "Out of the chaos Einstein's theories surfaced, and forces like the strong and weak nuclear interactions emerged," he says. He joins a growing clan of physicists, including Nobel prizewinner Robert Laughlin of Stanford University in California, who argue that the laws that we hold to be fundamental and the basis of reality are in fact emergent properties, spawned by the random chaos of the vacuum. It's a provocative statement but, in Volovik's view, there's nothing really radical about it. Think of an "empty" jar, which actually contains billions of air molecules jigging around and randomly bumping into each other. It's chaotic, but from this mess the properties we call temperature and pressure emerge. Couldn't the laws of space-time emerge in the same way? If Volovik is right, trying to find a theory of quantum gravity is a waste of time. He knows that's another message few people will want to hear: huge numbers of physicists spend their days trying to marry general relativity - Einstein's theory of gravity - with quantum mechanics. They hope such a theory will enable them to describe what happens when space-time, forces and matter are confined to tiny scales and endowed with enormous amounts of energy - as at the very beginning of the Universe. Without it, they say, we can never understand the birth of the Universe or the weird conditions at the hearts of black holes. But so far, no one has found a convincing theory of quantum gravity. "After 70 years of research, in spite of numerous achievements, quantum gravity is still far from realisation," says Volovik. He sees this as confirmation that it's simply not possible to "quantise" general relativity. In the highest energy conditions, the quantum gravitational field would become so swamped by the chaos of other particles and fields that it would be impossible to isolate anything that looked like gravity. He does have some support on this point. "It's speculative, but I think there is a very good chance that he is correct," says Matt Visser of Victoria University in Wellington. "It's possible that gravity is simply a low-energy approximation to something that is radically different at short distances and high energies. If this is the case,'quantum gravity'makes no sense at all." If so, scientists will need to change tack. The whole point of the exercise would be different, Visser says. The aim would be to find some quantum theory, no matter how bizarre, from which general relativity emerges at low energies. "This is very different from trying to quantise general relativity itself," he says.
And the powers of Volovik's oracle don't stop there. There are plenty of other questions helium can address, he says. Scientists would love to test a key prediction about black holes, for example. Theory suggests that black holes trap matter and even light inside a region called the event horizon. Nothing can escape. But in the 1970s, the British scientist Stephen Hawking showed that tiny amounts of energy leak from black holes as a result of pairs of particles popping up at the horizon. One half of the pair could fall in, while the other could escape. The escaping particle would steal some of the energy - effectively the mass - from the black hole. Eventually, the black hole might evaporate through this "Hawking radiation". The trouble is that this radiation is extremely weak. So weak, in fact, that a typical black hole in space would take far longer than the current age of the Universe to evaporate completely. Being realistic, astronomers have no hope of ever detecting Hawking radiation from black hole candidates in space. But some researchers now believe that carefully tuned flows of superfluids can mimic the physics of black holes (New Scientist, 18 March 2000, p 22). A flow of superfluid helium, for example, creates an "event horizon" wherever the flow of the superfluid is faster than the maximum speed of the quasiparticles. Like the photons of light that can't climb out of a black hole, the quasiparticles can't escape the superfluid's current. Volovik and his colleagues are planning to create a helium "black hole" using two superfluids sliding over each other. They showed earlier this year that this set-up can give rise to an event horizon for quasiparticles on the boundary between the two flows. Instead of a particle stealing energy from a black hole as Hawking radiation, a few quasiparticles can leak out by stealing kinetic energy from the fluid's motion (see www.arxiv.org/abs/gr-qC/0208020). Although this quasiparticle analogue of Hawking radiation may turn out to be too small to measure, it could provide the first chance scientists have to see some detailed black hole physics in action. Visser is inspired by this possibility. "The single most exciting aspect of all these analogue models is that they hold out the hope - not quite a guarantee - that we may be able to do laboratory experiments on analogue black holes in the not-too-distant future," he says. "Direct experimental evidence for analogue Hawking radiation would have a truly stunning impact.' Another problem Volovik is consulting his helium oracle about concems the accelerating expansion of the Universe. In i998, scientists announced results from observations of supernova explosions that suggest the expansion of the Universe is speeding up. It seems as though space exerts a repulsive force, sometimes known as the cosmological constant, through some kind of "dark energy" What's the source of the dark energy? No one really knows. A good guess might be that it stems from the energy of the seething vacuum. But if you use the equations of quantum mechanics to tot up just how much vacuum energy there should be in the Universe, adding the contributions from virtual particles and random fluctuations of fields, you get a huge figure. The strength of its repulsionshouldbeenormous-aboutl2O orders of magnitude too big to cause the observed acceleration. Flummoxed, many scientists blame the discrepancy on the highest energy fluctuations, which are a hidden factor because theorists haven't yet managed to calculate them. Some of these contributions would be negative. Could these contributions to the vacuum energy almost cancel out the others, leaving a very small cosmological constant? Yes, says Volovik -because helium says so. He doesn't even need to do an experiment to prove it. Imagine, he says, that people lived in superfluid 3He-A. "The people are made of elementary quasiparticles, just like we are made from elementary particles," he suggests. In superfluid helium the quasiparticles do not exert any kind of force on the atoms in the liquid. Because there's no interaction between the quasiparticle people and the helium atoms, the people would think they were living in empty space. If the quasiparticle people tried to compute the energy of their vacuum, by adding up the energies of fluctuations in the "empty space" atgund them, they'd get a huge answer. "When they compared their estimate with reality, they would also find that the estimate is many orders of magnitude too big," says Volovik. "So for them that cosmological constant problem is as puzzling as it is for us." But, from outside the helium cosmos, we can see all the components of the atomic structure - unlike in our Universe, nothing is hidden. And so we can calculate its various effects, Volovik says. The effect of the helium atoms, which mimic the effects of the highest energy physics in the Universe, is to counter the vacuum energy. When you add everything up, the total is a small value - and crucially, it's not zero, matching the small observed acceleration in the Universe's expansion. Another puzzle helium could help solve is this: why is the Universe dominated by matter, rather than antimatter, when theory says the big bang should have created equal amounts of both? Today, the antimatter is nowhere to be seen. Presumably, it clashed with the matter and vanished in a puff of radiation. But for any matter to be left behind to build stars and galaxies, there must have been slightly more matter than antimatter around. One leading theory is that, as the Universe evolved, the vacuum itself spawned a tiny excess of quarks over antiquarks. This was predicted back in the 196os and encapsulated in something known as the Bell-jackiw-Adler anomaly. If this bias really exists, it should show its hand in superfluid helium by creating a tiny, extra force on a spinning vortex. Volovik and his colleagues have confirmed in experiments that this force does exist. Once again, helium has confirmed that an equation which may describe events in the early Universe is correct. Volovik says helium can explain a host of other things. Why space appears to be completely flat, rather than curved as Einstein's equations say it easily could be, for example. Why galaxies are threaded with tangled magnetic fields. And which of the "fundamental" constants of the Universe, such as the speed of light, are genuinely fundamental and unchanging. So far, though, he hasn't gathered many disciples. He puts that down to an unhealthy divide between the physicists who play with general relativity and those who scrutinise the harsh realities of solid, real-world experiments. "The dirty solid body is in great contrast to the beautiful mathematical world of general relativity," he says. "For many people, the idea that general relativity is not fundamental and can be violated at high energy is unbearable." Ulf Leonhardt of St Andrews University is also trying to make artificial black holes. He thinks Volovik's only problem is his own cleverness. Most scientists just don't have a broad enough grasp of the issues involved to recognise the parallels between cosmological and superfluid theories. Leonhardt thinks Volovik's work is as sound and rigorous as it is provocative. Even those who are familiar with both condensed matter and general relativity have some reservations, however. According to Visser, fluids such as liquid helium serve as a fine model for about half of general relativity. The other half is less certain. He's unsure whether superfluid helium can really explain the cosmological constant, for instance. "There's room for debate there," says Visser. "There are several technical issues that seem to stand in the way of getting a clean version of the Einstein equations out of these analogue models. I think it's possible, maybe even plausible, but I do not see a rigorous proof." But such proofs may soon emerge. The European Science Foundation has created a programme called COSLAB (Cosmology in the Laboratory) to explore the links between condensed matter, particle physics and cosmology. Scientists from lo European nations are now tinkering with condensed matter such as superfluid helium to see what - if anything - it might tell us about black holes, the dark energy that drives the expansion of the cosmos, and defects in space-time. Of course, there's no guarantee that helium will expose the Universe's deepest secrets. But according to Visser, we should at least try to test some of the notions that nature has stubbomly kept out of our reach. The helium oracle might turn out to be one of the best ideas in physics, he says. "It is often quite remarkable how much really deep and fundamental physics can be found hiding in unexpected places",,* Further reading: Grigori Volovik's book Universein a Helium Dropletwill be published next year by Oxford University Press
NS 23 nov 02
Stray GM-plants spark anger
COMPANIES eager to generically engineer food plants to contain vaccines, drugs and Industrial chemicals have been shaken to their roots by last week's disclosure that "pharmed" crops have twice contaminated fields of soybeans. The revelation has pmmpted a wave of criticism ftm bcyth friends and foes of the agricultural blotech industry, and calls fbr more safeguards to pm-werrt drug-laced crops landing on the dinner table. The US Department of Agricufture and the Food and Drug Administmdon announced that they had found GM corn containing a pharmaceutical protein growing in tplots in Iowa and Nebraska this autumn. The GM corn had germinated from seeds left over ftm corn planted the year before by Texas-based company ProdiGene. The firm should have removed these plants under its govemmerft permit. "This is a failure at an elementary level," says Jane Rissier of the Union of Concemed SdentiStS in Washington DC. "They couldn't distinguish com ftm soybeans and remove them from a fleld. That's like failing nursery school.11 The union and other GM watchdogs had pre-Aously wamed that the US govemmertt rules fbf gmvWng pharmed crops were far too lax (New Scientist, 6 July, p 4). What genes the com contains is a company secret, and Prod!Gene couldn't supply a comment before NewSciendstwent to press. But the company's website says fis plants pmduce vaccines and human therapeutic proteins. To prevent the altered corn or arrj of its genes spreading, the US govemmerft has ordered the buming of 155 acres of surrounding com and the quarantine crf half a million bushels of soybeans harvested with the GM com, an estimated loss to the company of nearly $3 million. Prod!6ene also faces lines of up to $500,000. Even long-time advocates of plartt biotechnology are worried. Before the Prodi6ene invesdption, politically influential food-industry groups, such as the Grocery Manufacturers of America, were quietly suggesting drugs should only be grown in non- food crops to avoid contamination. Now they are speaking up. linddents like these can have ripple effects, says GMA spokesperson Stephanie Childs. "We don't want to lose lntemational markets because we can't assure the safety and integrity of the food supply.11 USDA spokesperson Ed Curiett says his agency vwll leam ftm the inddefit and dedde whether rules need to be tightened. "But the system seems to have worked," he says. Usee caught this crop berore lt entered the animal or human food chain.11 But Norman Mistrand, a plant geneticist at the University of California, Riverside, says the government was also ludty. @ if the GM corn had come up inside a cck -m fleld?'-' he asks. mit could have cross pollinated and you'd have no idea where it was.11 Philip Cohen
Bioweapons convention saved by a compromise
THE Biological Weapons Convention has been saved from becoming little more than a statement of intent. After a tense week of talks in Geneva, treaty members have agreed to continue annual meetings to discuss -voluntary efforts to enforce the treaty. But the discussions will not cover the worst biological threats. Last week's talks were aimed at salvaging the treaty as an intemational forum for controlling bioweapons. In 2001, a bioweapons treaty conference collapsed after the US rejected a legally binding agreement that would have imposed weapons inspections on members (New Scientist, i December 2001, p 11). After that, it was not clear whether any joint activities of treaty members would continue, as the convention itself calls for none. In September, US officials had said that November's meeting should decide only to hold another review conference in 2oo6, and threatened to name countries with bioweapons programmes if other signatories tried to achieve more. But last week they agreed on a compromise: member states will meet yearly, but only to discuss certain topics. Next year they will discuss laws to control pathogens and make the development and possession of bioweapons illegal. In 2004, they will discuss intemational efforts to monitor infectious diseases, and to investigate alleged uses of bioweapons. In 2005, they will discuss codes of conduct for microbiologists.
Oliver Meier of the Arms Control Association, a pressure group based in Washington DC, says these topics do not address the gravest threats. "I doubt codes of conduct are going to be what everyone is most concerned about in 2005," he says. He believes developments in science and technology that might lead to weapons, and the secrecy around such work, are more important. Also in Geneva last week, the ACA, together with other pressure groups, launched the BioWeapons Prevention Project (www.bwpp.org), a network of private organisations that will collect and publicise information about research and policies affecting bioweapons. Debora MacKenzie
What came first, bigger brains or lots of sex?
LOW fertility and frequent pregnancy complications may be the price that we have paid for evolving a large brain. For the fetus to get enough nutrients to grow a hefty brain the placenta has to aggressively invade a mother's uterus, says a new theory. But that can also provoke her immune system, causing dangerous complications. However, recent research suggests that exposure to a man's semen helps a women's immune system prepare for pregnancy (New Scientist, 9 February, P 32). So low fertility in humans reduces complications during pregnancy by giving a woman's immune system more time to adapt. Human fetuses spend 6o per cent of their energy on their brain, 3 times as much as other mammals. Twenty weeks into pregnancy, the placenta attacks the uterine wall for a second time, burrowing In more deeply than in any other mammal. But burrowing deeper is risky.
It can provoke the mother's immune system to attack the placenta, which is loaded with foreign genes from the father. This can trigger pre-eclampsia, where the placenta leaks toxins into the mother's circulation, causing blood pressure to spike dangerously. Within hours it can escalate into kidney failure, brain haemorrhaging and death. It Is thought that humans are the only mammals to suffer frequent pre-eclampsia, which occurs in 3 per cent of pregnancies. We are also far less fertile: a bitch that mates just once when it is on heat usually gets pregnant, yet women typically take six months to conceive. Research by Pierre-Yves Robillard, a neonatologist at Sud Rdunion Hospital on the Indian Ocean island of R6union, has shown that women who have sex with the father for over a year before getting pregnant have a 5 per cent chance of developing high blood pressure and pre-eclampsia compared with a massive 40 per cent chance for those who have only been having sex with the father for four months or less. Robillard is now proposing that this is why we are less fertile - the extra sex gives women a better chance of surviving the placental invasion. "If we had kept the same fertility as other mammals, we would have pre-eclampsia rates Of 20 per cent," he told a workshop about pre-eclampsia in Mauritius. "Humans could not have survived." The theory has generated both interest and scepticism. "It's an interesting idea that placental Invasiveness has something to do with brain expansion," says David Haig, an evolutionary biologist at Harvard University, "but other possibilities can't be eliminated.' For example, pre-eclampsia may have become more common as societies became better at caring for ailing mothers and babies. And Robert Martin, an anthropologist at The Field Museum in Chicago, questions whether invasive placentas are linked to larger brains. "Dolphins have a non-invasive placenta," he says, "yet the next biggest brain sizes after humans are found in dolphins." Douglas Fox
Love is the Drug
If you want to understand addiction, perhaps you need to explore some of the brain's more intimate secrets, says Mala Szalavitz
SONGWRITERS frequently compare love and addiction. Addicts compare wanting drugs to wanting sex. And scientists who study addiction are now beginning to agree with both. Stimulants like cocaine act on the brain's dopamine system, and so mimic the thrill of desire and anticipation. Depressant drugs like heroin, on the other hand, produce the opposite kind of pleasure - a dreamy satiation and freedom from pain, caused by their action .on the brain's opioid system. A speedball, a cocktail of cocaine and heroin, can be likened to a rapid, hyped-up sex simulation, moving rapidly from desire to climax. Because of this powerftil ability to simulate the most intense thrills, it is often said that drugs can hijack the brain's pleasure, reward and motivation systems, leaving addicts overwhelmed by craving for the drug, and willing to do anything for their next fix. It's racy parallels like these that have led a few intrepid souls to stake their reputations on the idea that we could perhaps leam more about addiction by studying sex and love than the drugs themselves. If we want to know how drugs derail our pleasure and reward systems, we first need to know what those systems are, and how they behave. According to neuroscientist Annarose Childress, what those systems usually do is control our sexual behaviour. Childress, of the University of Pennsylvania, is one of a group of researchers who believe the reward system must have evolved to get animals interested in sex. "This circuitry has been well preserved throughout evolution to enable animals to eat and reproduce," she says. "Those functions have been around long before cocaine and opiates." To understand addiction, we need to find a way to study these parts of the brain as they do what comes naturally. Not surprisingly, it's been quite tricky persuading funding bodies and universities of the potential benefits of showing pornography to brain-scan volunteers, allowing people to misbehave inside a scanner, or measuring sex hormone levels during drug taking. But a few researchers have done it. They argue that if we know the anatomy and chemistry of normal sexuality, perhaps we could find how addiction starts to drive behaviour and how desire turns into cravings that addicts simply can't ignore. Perhaps understanding our sex drive will one day provide the key to treating addiction. Studies of animals have given researchers good reason to suspect that there is a link. One recent study on rodents, for example, likens the bond between mates to an addiction. Larry Young, a behavioural neuroscientist at the Yerkes National Primate Center in Atlanta, says that high levels of a receptor called VlaR in a brain region called the ventral pallidum are associated with monogamous behaviour in one type of vole; other voles with fewer of these receptors seek multiple partners. It seems as though the monogamous voles get more pleasure from their partners, while the promiscuous voles get more joy from novelty The ventral pallidum also plays a part in reward and addiction. The region is active when rodents learn to give themselves shots of drugs and when they are in places they associate with getting their fix. Monogamous male voles seem to become addicted to a particular female, says Young, perhaps associating her with some sort of rewarding feelings in the same way that animals may come to associate a place with the rewarding sensation of drugs. "The neural circuits underlying addiction did not evolve to respond to drugs," he says. "Drugs simply modulate the natural reward circuits that have evolved to ensure that animals do all the things that they should do, such as eating, sex and forming social attachments!' When you have such compelling animal models, and sex and drugs are so frequently mentioned in the same breath, it's surprising that it has taken so long to make similar comparisons in the human brain. Yet just this month two different groups of researchers told the annual meeting of the Society for Neuroscience in Orlando that brain regions implicated in addiction are also active during arousal, orgasm and ejaculation. The delay has not just been because of the technical difficulties of doing experiments. It took Mario Beauregard from the Neurological Institute of the University of Montreal three years to get some of the first studies that imaged sexual arousal in the brain published. More than one highbrow journal told him the findings were "not of general interest". His latest study, which appeared this year in Human Brain Mapping (vol 16, p 1) uses functional magnetic resonance imaging (fmri) to explore which brain areas become activated when men and women view erotic films. Not surprisingly, the visual areas are busy; but so too are many evolutionarily ancient circuits associated with emotion - the limbic system, anterior temporal pole and amygdala, and a region of the orbitofrontal cortex (OFC). Previous research found that these areas are important in prioritising, decision making and giving emotional colour to an experience, and may subconsciously trigger physiological responses and desire. just last year, Childress revealed that these same circuits were also critical in cocaine addiction. just as with sexual desire, strong feelings can be triggered by what people see - needles or crack pipes can induce strong craving, even in addicts who've been clean for years. But addicts find it much harder to control their desires than most jilted lovers confronted with a picture of their ex. So while Beauregard has been trying to understand how these circuits regulate our emotions, Childress has been trying to see how they work in addicts'brains. Beauregard's group used fMRI to image men's brains. In one experiment the men were shown porn films, and sometimes asked to try to inhibit their arousal; at other times they were encourages to enjoy it. In another study the men were asked either to control or wallow in feelings of sadness. When they inhibited their emotions, the limbic activity disappeared totally, while higher brain areas such as the cortex - especially in the frontal lobes - remained active. Childress suggests that the same might be true for controlling a desire for drugs. She finds that when addicts learn to fight their cravings by considering the damage drugs could do, activity in the OFC goes up, but declines in the amygdala. "The OFC is important for putting on the brakes, looking at consequences," she says. She has already found that cocaine addicts have less grey matter in their OFC than non-addicts - but whether the missing matter makes people vulnerable to addiction or is caused by drugs is unclear. The next step is to compare people who can control their sexual behaviour or drug use with those who cannot, in the hope of rooting out the essence of compulsive behaviour and self-control - and how it can be influenced by drugs. And it's not just looking at the way the brain is wired for sex and love that's giving addiction researchers a few leads. The complex mix of neurochemicals and hormones involved might give some useful information about how addicts could be helped to control their desires too. One important chemical is dopamine. The common pathway affected by drugs of abuse is the dopamine system linked to a brain region called the nucleus accumbens. Whether it's nicotine, cocaine, heroin or alcohol, the more directly or profoundly a drug affects the dopamine system, the more craving and pleasure it produces.
"The neural circuits underlying addiction didn't evolve to respond to drugs. Drugs simply modulate the natural reward circuits that evolved to ensure animals eat and have sex"
Cocaine and other stimulants act on brain circuits that signal the presence of something pleasurable - such as sex. Addicts appear to have some differences in their dopamine systems. For example, recent studies by Nora Volkow and her team at the Brookhaven National Laboratory in New York found that many addicts seem to have fewer dopamine receptors than non-addicts. There is also some suggestion that certain gene variations may make neural signalling via dopamine less effective in addicts. Both problems might predispose people to seek ways of boosting an underactive pleasure system, making drugs especially attractive. But while addiction researchers have pitched dopamine as the brain's best dope and key to all joy, it might not be that simple. Dopamine's main brain function, in fact, seems to be controlling movement rather than mood - which is why the progressive loss of dopamine neurons in people with Parkinson's disease primarily causes movement disorders, not an inability to feel pleasure. But the two aren't entirely separate. Wanting to feel good cannot be disentangled from the motivation to create that feeling. "When you think about it, it makes sense that when you are attracted to things, your natural instinct is to move towards them," says Jim Pfaus, a psychologist who studies dopamine and sexual behaviour at Concordia University in Canada. Dopamine is also released in anticipation of a reward - it rises when addicts see cocaine, when people see tempting food and during sexual desire, so it maybe more linked to believing reward is close than to signalling satisfaction. Or it may correspond to different aspects of pleasure when expressed in different parts of the brain. Pfaus is now studying the chemical sequence that plays out as an animal moves from desire to satiation during mating, in an attempt to fully understand this relationship. One surprise has been that dopamine responses seem to vary between males and females, at least in rats. Could there be differences in the way men and women become addicted too? It's a consideration addiction research has neglected for too long, thinks Jill Becker, a psychologist at the University of Michigan. In male rats, she says, dopamine levels go up when they smell a female, see her or have sex. "Anything to do with being introduced to a female, dopamine goes up," she says. But female rats only get a "hit" of dopamine when they can control sex. That scenario doesn't usually happen with caged animals, but in the wild, females normally allow the male near, then flee, returning a few times, before they will eventually accept his advances. This "pacing" ensures the rat is optimally primed for pregnancy. A release of oestrogen sensitises the dopamine system, so it will give her a "kick", and simultaneously maximises the odds of successful conception. "In terms of drug addiction," says Becker, most work has been done in males.' It's not hard to argue that in men drugs may simply take over the reward system and replace the drive for sex with a drive for drugs, she says. Male addicts may pursue drugs with the single-mindedness with which other men pursue sex; getting high gives them the sense that they are on track to getting satisfaction, so they do it again. Repeating this sequence may make it harder and harder to stop. "But," says Becker, "the female is more interesting. During sex, dopamine doesn't always go up. It requires the social and physical context to be right.' This could mean that cravings in women could vary with their hormones and that different addiction treatments may be needed for them. Exploring the links between sexuality and addiction has also thrown up another hormone that might be critical in the reward system. Oxytocin is important in forming bonds between mates and between parents and their offspring. The hormone's levels also spike during orgasm - and all are highly rewarding activities. oxytocin researcher C. Sue Carter of the University of Maryland and her team found that in monogamousvoleswherethemaleshelp with childrearing, "good dads" have more oxytocin than promiscuous ones who love'em and leave'em. And low levels of oxytocin may be partly to blame when cocaine-addicted rats - and perhaps even humans - neglect their offspring. Even more intriguing, oxytocin seems to both prevent rodents becoming tolerant to heroin and reduce the overactivity usually induced by cocaine. It even cuts heroin- withdrawal symptoms, according to Gabor Kovdcs and colleagues from the Markusovszky Teaching Hospital in Hungary. The oxytocin connection could explain why falling in love - which might mean raised levels of the hormone - has helped many an addict quit their habit. So maybe love will provide a happy ending. Or perhaps it will take sex too - or at least an understanding of its chemistry and effect on the brain - to inspire new ways of treating addiction. Addiction researchers can't afford to be prudish if they really want to understand how our brains work.
Mala Szalavitz is a writer based in New York and co-author of Recovery Options. The complete guide (Wiley, 2000)