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NS 3, 24 aug 02

Natural high helps to banish bad times

ALISON MOTLUK

OUR brains may do the equivalent of rolling themselves a joint when they want to forget something awful. The body's own versions of the active ingredient in cannabis may help extinguish unwanted memories. Marijuana has been used medicinally for thousands of years, and people with certain psychiatric conditions such as schizophrenia are more likely to smoke pot than healthy people (New Scientist, 29 MaYl999,P7). The active chemical in marijuana, tetrahydrocannabinol or THC, binds to the brain's cannabinoid receptors, which are known to be linked to pain sensations, emotion and movement. And in the past decade, researchers have identified chemicals made within the brain thataresimilartoTHC. Now Beat Lutz at the Max Planck Institute of Psychiatry in Munich and his team have found that these cannabinoids play an important role in getting rid of unwanted memories - at least they do in mice. The researchers genetically engineered mice so that they lacked a particular type of cannabinoid receptor caged CBi. These are normally found in the amygdala, a brain region associated with fear. They then conditioned the mice, as well as their normal litter mates, to associate a particular musical tone with an electric shock. Both groups of mice quickly teamed the association, freezing with fear whenever they heard the tone. A week later, the mice were repeatedly exposed to tones but without the associated electric shock. The normal mice soon shed their fear response, but the modified mice still showed fear ii days later. The researchers found that the modified mice eventually suppressed the bad memories, but it took them about six times longer than the normal mice (Nature, vOl 418, P 530). Lutzs group also showed that blocking CB1 receptors in the normal mice meant they were unable to stamp out the negative association. The team later studied the mice's amygdalae, and confirmed that animals who were now unleaming the unpleasant association had significantly higher levels of two majorcannabinoids-anandamide and 2-arachidonoylglycerol -than those who'd never been trained. It suggests that these chemicals help wipe out bad memories by binding to CB1 receptors. The finding may lead to new treatments for people who have related mental conditions. "We could understand the problem of phobia or post-traumatic stress disorder by investigation of this cannabinoid system," says Lutz. He points out that marijuana itself is too blunt an instrument to be a potential treatment, because it activates all the brain's cannabinoid receptors at once. "It's an important paper," says neuroscientist Daniele Piomelli at the University of Califomia, Irvine. "It's going to have a big impact in the field."

Stem cells could save sight

INJECTING stem cells from bone marrow into the eye might help prevent many kinds of blindness. A team at the Scripps Research Institute in La jolla, Califomia, have shown that a type of stem cells known as endothelial precursor cells can be used both to prevent the degeneration of blood vessels in the eyes of mice and, if genetically modified, to discourage excessive growth. "We were beside ourselves with excitement," says Martin Friedlander, who led the research. Many eye diseases are triggered by vascular problems. The inherited disease retinitis pigmentosa involves degeneration of the retinal blood vessels. And the leading causes of vision loss in developed countries - age- related macular degeneration and diabetic retinopathy - are both caused by a proliferation of vessels in the eye. Endothelial precursor cells, which reside in mouse bone marrow, are known to encourage the formation of blood vessels during development. So Friedlander's team tried injecting EPCs into the eyes of mice. They found that the cells migrated to the blood vessels in the retina. In healthy eyes, the cells had no effect. But in mice with a genetic defect in which retinal blood vessels deteriorate with age, the cells incorporated themselves into the vessels and prevented any degeneration. These mice had normal retinas 33 days after birth, whereas in mice that were injected with another type of bone marrow cell, the deep blood vessels were nearly all gone by this stage. Friedlander's team also showed that EPCs modified to produce a protein that inhibits the growth of blood vessels could stop new retinal blood vessels forming when injected into the eye. This suggests the cells could help treat proliferative as well as degenerative vascular eye diseases (Nature Medicine, DOI: 10-1038/nm744). However, it's still not clear whether similar EPCs can be purified from human bone marrow. And Friedlander cautions that eye diseases often involve nerve damage as well as abnormal blood vessels. Philip Cohen, San Francisco

Their hands on your genes

Greedy? lm moral? Forget it, there's nothing wrong in principle with patenting human DNA. It all depends on how you do it, says Sandy Thomas

THOUSANDS have been granted overthe past decade, not just to industry, but to universities and research institutes as well. Nevertheless, is it right? To date, the debate over the patenting of human DNA has largely consisted of stating and restating entrenched positions: industry, keen to protect investment, is on one side; on the other a mix of NGOS, scientists and other people, who see human DNA as a common heritage that should be protected from commercial exploitation. But there is a tenable middle-ground position, and last week my colleagues and I attempted to outline it in a new report from the Nuffield Council on Bioethics. Our report does not say that patenting genes is wrong in principle. What it concludes is that far too many gene patents are being granted by a system that is failing to apply the rules strictly enough. The purpose of patents is to stimulate innovation for the public good and reward people for new inventions. But many new patents for human DNA are likely to impede innovation and create powerful monopolies capable of charging over the odds for tests and drugs based on human genes. Patents involving human DNA should be granted only in rare cases. They should be the exception rather than the norm. How did we reach these conclusions? The most common objection to this type of patent is that human genes occur naturally: they are there to be discovered and not invented. This is not persuasive. Isolated DNA does not occur naturally, and without isolating and cloning a gene, you cannot decipher its sequence. Moreover, the patent system has long recognised useful applications of discoveries as inventions. So patent offices are right to conclude that DNA can be considered part of an invention. But it does not follow from this that all patents on all human genes should be allowed in all circumstances. The key question is where to draw the line. Inventions must pass three tests to qualify for a patent.

They must be useful, novel and not obvious to someone familiar with the field. To look at how these criteria should apply to genes, we distinguished between four different uses of DNA sequences: in genetic tests, as research tools, in gene therapy and for producing therapeutic proteins. First, genetic testing. Heated controversy continues over an American company called Myriad Genetics and its patent for the breast cancer genes BRCAL and BRCA2. The company is charging $2,400 a time to test patients and claiming royalties from others who offer tests based on the same gene. But finding a link between a gene and a disease is not itself an invention: it is a discovery. And once such a link comes to light, it is obvious that the gene might form the basis of a genetic test. There is little inventive about it. That is why we concluded that gene patents based on claims about diagnosis should seldom be granted. The same reasoning should apply to patents that are based on claims about gene therapy. Once a gene has been linked to a disease, the notion of using it in a treatment is obvious and shouldn't merit the reward of a patent. Patents should be reserved for those who invent safe and effective methods for getting genes into tissues. Also to be discouraged are patents on genes of unknown medical value. These days, scientists can identify human genes by trawling through databases of human DNA and making "best guesses" about the biological functions and potential uses of the genes they find there. But without further work, such genes are research tools, not inventions. And past experience suggests that allowing speculation to pass for actual evidence of usefulness is a recipe for hindering research. The salutary lesson involves the human gene for a receptor known as CCR5. In 1995, a US compa-Tiy called Human Genome Sciences applied to patent the gene for its usefulness in combating viral infections, solely on the basis of its similarity to known DNA sequences. Shortly after, researchers elsewhere discovered that the receptor was HIV's passport into cells. So because of the speculative patent it holds, Human Genome Sciences is entitled to levy royalties from companies that use the receptor to look for potential HIV drugs. One type of gene patent is acceptable, however. Companies and labs should be allowed to own the rights to genes whose protein products are used directly as medicines, such as human insulin or erythropoetin. The information encoded in such genes is being used to make something of value, and it is clearly in the public interest to create incentives to encourage the costly process of developing a medicine. But since genes often carry the instructions for more than one protein, there is a caveat. The rights to the gene should only extend to one protein. Are these recommendations realistic? Most do not require new laws. They could be achieved by applying the existing criteria for patents more stringently. Without this, we face the prospect of more attempts to monopolise genes, more high prices for gene tests, and the tying up in legal red tape of ever more human DNA sequences. * Sa n dy Thom as is d irector of the Nuffield (ou ncil on Bioeth ics a nd senior fellow at SPRU, University of Sussex. Copies of the report a re availa ble at www. n uffield bioethics.org

Can the human race live forever?

Yes, says philip Ball, butonly if einstein was wrong about our universe

KATHERINE Freese and William Kinney don't look much like superheroes, but this pair of astrophysicists may just have rescued all life in the Universe. And as in all the greatest comic book stories, deliverance has come before most of humanity even knew they needed saving. A couple of years ago, two other physicists announced that the latest cosmological discoveries meant that life in our Universe was doomed. Now Freese and Kinney tell us that it can go on forever. The ultimate future of life may seem a strange thing for physicists to be debating, but the behaviour of the Universe can tell us about more than just time and space, galaxies and supemovae. Our future in the cosmos is not just a matter of chance circumstances or our own ingenuity. It is circumscribed by the most fundamental laws of nature, written into the fabric of the Universe during the big bang. Using physics to work out our fate may be a tad speculative, but it's not unprecedented. Freese, of the University of Michigan in Ann Arbor, and Kinney, who is at Columbia University, New York, are building on work done by the Princeton physicist Freeman Dyson. In 1979, Dyson published a study on the thermodynamics of life, using physics to argue that life could last forever in the Universe. His argument is really about life that has consciousness: life that thinks. At some level, thought must be like computation, he says, involving the physical processing of information. Any practical computation depletes its energy source. Dyson assumed that the Universe doesn't hold inflnite sources of energy, so any life would eventually face an energy crisis. But he argued that an organism can stretch out a dwindling energy supply by slowing its metabolism, which is equivalent to operating at a lower temperature, and slowing down the rate at which it performs computations. In other words, it can save energy by thinking more sluggishly. But even cooling down - and thus slowing down - can't eke out a finite energy resource forever. That's because there's a limit on how cold anorganismcanget. Every computation produces heat that has to be radiated away. In order to do this, the organism must remain warmer than its environment, because heat can only flow from a hot object to a cold one. The cosmological data of Dyson's time indicated that the temperature of the cosmos was dropping more quickly than would the operating temperature of any organism trying to keep thinking. Sofar, so good. However, Dyson also realised that, because radiating away heat relies in general on the properties of electrons, quantum mechanics dictates a fundamental limit to how fast the heat can be dissipated. If the organism produces heat faster than its electrons can dissipate it, it is doomed to death by overheating. The answer, said Dyson, is to "hibemate". In Dyson's definition, a hibemating organism essentially stops its metabolism entirely, which means it must stop thinking. Yet it continues to radiate away accumulated waste heat. He showed that a judicious combination of periods of ever- slower activity and spells of hibernation make it possible to perform an infinite number of computations with a finite amount of energy: the organism can go on thinking forever. So, the outlook for life - albeit a strange, sluggish and cold kind of life - is good. Or so we thought. But bad news was on the way. Recent observations of distant supemovae have shown that the expansion of the Universe, which has been going on since the big bang, is speeding up (New Scientist, ii April i998, p 26). That's a problem, as it means our future energy sources may be slipping out of our grasp. In an expanding Universe, the further away an object is from us, the faster it is heading into the distance. At a particular distance, known as the de Sitter horizon, objects are receding at the speed of light. Anything beyond the de Sitter horizon is forever out of reach, Sp, bec,ause of cosmic acceleration, distant parts of the Universe will eventually reach the point of no return. Every galaxy beyond our Local Group-which gravity keeps bound together-is moving inexorably towards our de Sitter horizon. Once they pass it, their light can never reach us. That means the galaxies wfll wink out one by one. The space beyond our galactic neighbourhood wig begin to appear cold and dark, and we'll no longer be able to find out anything about it (New Scien tist, 20 October 2001, P 36). That's not just a problem for astronomers of the year two trillion. It means that when a galaxy disappears over the de Sitter horizon, we lose a potential source of eneru. T'he same is true everywhere. AR life, wherever it Is in the Universe, faces a dwindling eneru supply. As Dyson showed, it seems that life can survive such a setback by slowing down its metabolism and hibernating periodically. But the de Sitter horizon does more than create an eneru crisis. In the wrong circumstances, it can set a limit to how cold the Universe can get. And if you are a creature trying to operate at ever-lower temperatures, this is very bad news indeed. The problem stems from a suggestion first made by Stephen Hawking. Whenever there is a horizon beyond which one cannot see or travel - be it a black hole's event horizon or a de Sitter horizon - this boundary emits a small but significant amount of radiation. The radiation comes from quantum fluctuations that occur in the vacuum of space. These fluctuations continually create pairs of particles and antiparticles. Ordinarily, these particles annihilate one another immediately. But if a pair pops into being close to a de Sitter horizon, one particle can wander over the horizon and became Irrevocably separated from Its partner before they can cancel each other out. And so one half of the pair is left, adding a contribution to the heat eneru in the accessible Universe on our side of the de Sitter horizon. This means that space in an accelerating Universe can never get cooler than a particular temperature, known as the Hawkingtemperature. it's hardly a balmy glow: working from what the supemova data reveals, It'll be something of the order of i@ kelvin. Nevertheless, as we lower our operating temperature to slow down our metabolism, we are eventually going to hft a point where we reach the same temperature as our envirorunent. Then we won't be able to radiate away waste heat. In other words, although we might be extremely cold, we'll still fry the moment we try to think. Cosmologists John Barrow and Frank Tipler were the first to point out this disastrous scenario in their book TheAnthropk Cosmological Principle. And then, In 2ooo, Lawrence Krauss and Glenn Starkman of Case Westem Reserve University in Cleveland, Ohio, published a much more detailed analysis. Their conclusion was stark: given Dyson's scenario, nothing - not mining the Universe for fts energy resources, not even hibernation - could preserve life forever in an accelerating Universe. But Freese and Kinney have come to the rescue. Krauss and Starkman were looking at what would happen if the Universe's accelerating expansion were being driven by a particular forin of energy: the vacuum eneru created by a "cosmological constant". This constant, whose existence was ftrst suggested by Einstein, Is a measure of how much eneru is released In empty space when the paired particles and antiparticles created by the vacuum's quantum fluctuations annihilate each other. T'he cosmological constant - if it eidsts - endows empty space with a repulsive force that causes space-time to expand. it's the explanation for the Universe's accelerating expansion that most physicists favour, but there are problems with it. Einstein only proposed fts existence to make his theory of general relativity fit the (mistaken) assumption of his time that the Universe was static. And no one can explain why the cosmological constant has the value ft apparently does: according to conventional theories, it should be iom times larger than astronomical observations suggest. The cosmological constant is by no means the only way to explain the acceleration. There's "quintessence", for example. This idea was first proposed in i987 by a group that included Freese. The quintessence theory suggests that the eneru responsible for the acceleration of the Universe comes partly from the vacuum enerU and partly from dark matter, the unobservable - and, as yet, Inexplicable - stuff that astronomers must posit to explain why galaxies rotate as they do. The useftil thing about quintessence is that the eneru accelerating the cosmic expansion need not be constant. "quintessence is a vacuum energy that changes in time," Freese says.

Our freezing future

The vacuum energy determines the energy of the particle-antiparticle pairs created by quantum fluctuations of empty space. And this, in tum, determines the temperature that an accelerating Universe is destined to reach once all other sources of eneru have disappeared over the de Sitter horizon. So if the vacuum eneru is steadily falling, as the quintessence idea suggests, the temperature of the Universe keeps falling too. There's no temperature lin-At that would place a limit on life's longevity. Another model that Freese has developed is Cardassian expansion, named after the reptilian bad guys of Star 7rek: Deep Space Nine. Like the theory of quintessence, Cardassian expansion allows the temperature of the Universe to keep falling, but unlike quintessence or the cosmological constant ft doesn't invoke vacuum enerU. "The only ingredients are ordinary matter and radiatiorl:'Freese says. It might sound like a rather convenient construction, but it is actually a consequence of "brane physics', a new idea that is fast gaining credibility. Many physicists now think our visible Universe of three spatial and one time dimension is just one membrane, or brane, embedded in a space that has six or more dimensions (NewScientiSt, 29 September 2ooi, p 26). When Freese and Daniel Chung of the University of Chicago were looking into this idea, they noticed that the extra dimensions would pull on the brane that we know as our Universe. Working with Michigan graduate student Matthew Lewis, Freese has shown that the pulling of the extra dimensions can in fact cause our Universe to accelerate. The consequences of this Cardassian expansion fit with observational data such as the cosmic background radiation and the age of the Universe. And Cardassian expansion wiu also allow us etemal existence. Since there is no vacuum energy in this model, the Universe is simply filled with normal matter and radiation. Our once-hot Universe will cool forever, moving inexorably towards (but never reaching) absolute zero. As long as an organism keeps pace with the background temperature, never cooling below it, it will always be able to radiate away the waste heat generated by computational operations, and keep on going. So, although the Universe seems to be accelerating, that needn't be the life-ending catastrophe that Krauss and Starkman predict. "We discovered that any driver of acceleration other than a cosmological constant can probably allow life to persist indefinitely," says Freese. Krauss and Starkman's pessimism isn't beaten yet, though. They say that when things get very cold quantum-mechanical effects suppress an organism's ability to radiate away heat, regardless of the background temperature. To lower its energy, an organism must be able to descend onto a lower rung of the ladder of quantum energy states. But, say Krauss and Starkman, the rungs cannot go on forever. Eventually an organism must reach its quantum ground state, and then it has nowhere to go. They raised this as an objection to Dyson, and think it applies to Freese and Kinney's arguments too. Kinney thinks cosmological models that involve an ever-changing "dark energy" can provide a way around this difficulty. "if you make space itself dynamic, the expansion of the Universe makes new quantum ground states available to the system, and you can beat Krauss and Starkman's limit," Kinney says. He admits it's a hand-waving argument, based on the fact that the ground-state energy of quantum particles is lowered as they become less tightly confined in the expanding Universe. The matter is far from settled, Kinney says. "Nobody has yet made these kind of arguments really rigorous, so their validity is still a very open question.' All the physicists involved are still locked in debate over the issues. And since the discussion is based on cosmological speculation, very simple definitions of life and the slippery nature of the Universe's hidden energy, at the moment it would be unwise to lay bets on whether or not we'll reach eternity. Kinney concedes that it's something of a playful diversion from the more ponderous side of cosmology, "especially for somebody like me who was raised on science fiction and comic books," he says. Some might say SF has even inffltrated the paper Freese and Kinney have submitted to Physics Letters. The pair have gone so far as to suggest a few far-fetched emergency plans to save the human race (see "The great escape"). But no one is panicking yet. The possible extinction of life in the Universe is not going to be a pressing issue for at least 1040years. "The timescale in question is immense," says Krauss. "It's nothing to sell your stocks about' " 0 PhilipBallisafreelancewriterandformerassociate editor at Nature Furtherreading: "The ultimate fate of life in an accelerating Universe" by Katherine Freese and William Kinney, www.arxiv.org/abs/astro-ph/0205279 "Life, the Universe, and nothing: life and death in an ever-expanding Universe" by Lawrence Krauss and Glenn Starkman, AstrophysicaiJoumal, vol 531, p 22 (2000)

Seed firms bungle field trials

KUffr KLEINER

THREE separate seed companies have made mistakes in field trials of genetically modified crops in the US and Britain, raising questions about the standard of quality control in thousands of open-field tests. In Hawaii, two companies failed to follow regulations designed to make sure pollen from GM maize doesn't contaminate other crops, according to the US Environmental Protection Agency. And in Scotland, a seed company discovered that the GM canola, or oilseed rape, it was testing contained a small amount of another kind of GM rape that wasn't supposed to be there. The incidents are the latest in a long series of errors and mix-ups involving GM crops (New Scientist, 23/3o December 2000, p 22), although in none of these cases has there been any evidence of harm to the environment or human health. Last week, the Center for Science in the Public Interest in Washington DC published letters sent by the EPA to Mycogen Seeds and Pioneer Hi-bred Intemational. The EPA says they didn't follow proper procedures while setting up test plots in Hawaii for a root-worm- resistant maize that has a gene for a bacterial toxin. In particular, Mycogen failed to plant trees to act as a windbreak and didn't plant a buffer of hybrid corn to prevent pollen spread. And Pioneer Hi-bred planted maize in an unapproved location, too close to other crops. A Pioneer Hi-bred spokeswoman denies the company broke any rules. Mycogen says it is investigating the matter. The incidents are worrying because the US doesn't fully assess whether GM crops are safe to eat until after field trials have been carried out. With other experimental crops there might be a risk to human health if food crops near trial sites were contaminated by stray pollen, although in this case the toxin from the added gene has been shown to be safe to eat. Earlier this month, the Bush administration did propose tightening the rules, so that companies would have to submit details to the EPA and the Food and Drug Administration about novel proteins that might cause allergies before trials take place. But even if the proposals are accepted, they won't come into force for months. In Britain, food safety assessments are carried out before field trials. But that doesn't help if the wrong crop is planted. Aventis CropSciences mixed up the seed for a herbicide-resistant rape approved for fleld trials with seeds from an unapproved variety that contained genes for antibiotic resistance. The level of contamination was lOw - just 3 per cent - and other crops with these genetic modifications have already been grown commercially in other countries without any problems. Nevertheless, Aventis's admission sparked a media furors. Britain's Department of the Environment, Food and Rural Affairs says it wig consider toughening the rules and checks on seed purity. Watchdog groups say the incidents raise serious concems about safety. "This is another example of the industry's inability to regulate the pollen flow and the gene flow of these crops, and to follow the recommendations and guidelines they and the agencies have worked out to protect public and environmental health," says Doug Gurian-Sherman of the Center for Science in the Public Interest.

Split brain reveals our sense of self

YOUR brain's ability to identify familiar faces has an interesting quirk. While the right side of the brain recognises other people, it's the left side that knows you're you. Experiments show that our right brain is far better at recognising familiar faces such as friends or celebrities than our left brain. But according to David Turk at Dartmouth College in Hanover, New Hampshire, it hasn't been clear which brain hemisphere recognises its owner most easily. To find out, he and his team enlisted the help of a "split-brain" patient, "JW" ' His two brain hemispheres can't communicate because the connections between them have been surgically severed, to combat severe epilepsy. Only the left side of his brain responds to things he sees in the right visual field, and vice versa. The researchers took a photo of JW and "morphed" it to varying degrees with a photo of one of their team, Michael Gazzaniga, whom JW had known for more than 20 years. Then they showed the original photos and nine intermediate morphs to IW, in his right and left visual fields in turn. By pressing a button, IW had to answer the question: is that me or is that Mike? It turned out that JW's right brain had a bias towards identifying morphed faces as Mike, but the left side did the opposite, favouring himselE To make sure the effect wasn't just something to do with Mike's face, the team repeated the tests by morphine photos of IW with Bill Clinton, George Bush and someone else JW knew personally. The results were similar to those in the first experiment (Nature Neuroscience, DOI: 10.1038/nn9O7).

Turk concludes that the left brain is specially geared up to recognise 11 me" while the right side registers "not me" ' The fact that there's a separate, specialised way of identifying yourself is not surprising, says team member Margaret Funnell, because a distinct sense of self is essential to human intellectual abilities, such as introspection and self- consciousness. "I don't knowhow someone could live in a community without that," she says. Hazel Muir

Your family really does stink

The smell of relatives, the perils of travelling with the opposite sex and the reason why some lovers are jealous:

Alison Motiuk reports some intriguingfindings

PEOPLE can recognise the smell of their close family members - but surprisingly, they don't like it. This aversion may help prevent incest, the discoverers speculate. Most studies of smell recognition in humans have looked at mothers and their newbom babies, who leam to recognise each other's smell soon after birth. But Tiffany Czilli's team at Wayne State University in Detroit wanted to know how well all the other members of the family would fare in a sniff test. She recruited 25 families with at least two children aged between 6 and 15, and gave the participants odourless T-shirts, odourless soap and resealable bags with their names on them. The volunteers were instructed to sleep in the T-shirts for three nights, wash only with the soap provided and seal the shirts into the plastic bags each morning.

CziUi then asked everyone to sniff two T-shirts,onewombyafamflymember and one by an unknown and unrelated person. She asked fathers and mothers if they could detect the scent of their children, and children if they could ident@ their parents or siblings. She also asked each of the participants which odour they preferred. Both mothers and fathers recognised their pre-adolescent offspring, CziUi found, though mothers tended to be more accurate. Neither parent could distinguish between their children, however. For their part, pre-adolescent children aged 5 to 8 did not recognise their mother's smell, while older children, aged 9 tO 15, did. Breastfed sons were the exception: they could recognise their mothers. And all the children recognised dad's smell.

When asked which smells they liked, the answers were even more intriguing. The volunteers far preferred the smens of other people to those of their ovrn family members. Mothers especially disliked their children's smells, while children had a strong aversion to their dad's scent. " Recognition and preferences can operate Independently," Czini says. She thinks that dislfflng the smell of close family might be part of the mechanism that helps prevent incest. Particularly notable is the fact that opposite-sex siblings disliked each other's smells, while same-sex siblings did not. She also speculates that the aversion to dad's odour could reflect social distancing and independence in the child. The avoidance of inbreeding could definitely be at work, says Dustin Penn at the University of Utah in Salt Lake City. But he wams that asking people about their preferences can be unreliable. "Just because people say they'prefer' something doesn't mean theyll act in a preferential way," he says. Smell preference is context dependent, he adds. Liking someone's smell doesn't always mean you'd like to sleep with them. *

Why there are always two sides to love

THE more asymmetrical you are, the more likely you are to be a jealous lover. just about everyone is lopsided to some extent. Hormone imbalances in the womb, for instance, can lead to one foot being bigger than the other. B years, a series of animal and human studies have suggested that the implications of asymmetry go far beyond struggling to find shoes that fit both feet. It seems that people who are more symmetrical are not only healthier, more fertile and perhaps even smarter - they are also more attractive. This led William Brown at Delhousie University in Halifax, Nova Scotia, to wonder about jealousy. "If jealousy is a strategy to retain your mate, then the individual more likely to be philandered on is more likely to be jealous," he speculated. And if peoplewho are less symmetrical are less desirable, they are more likely to be cheated on. To test his theory, Brown looked at 5o men and women in various kinds of heterosexual relationships, comparing the sizes of paired features such as feet, ears and fingers. The volunteers then filled in a questionnaire already used in other studies to assess romantic jealousy. He found a strong link between asymmetry and romantic jealousy. Asymmetry could account for over a fifth of the variation in romantic jealousy from person to person, he says. To make sure less symmetrical people aren't simply cursed with more jealous personalities, Brown also assessed their propensity to be jealous outside the relationship, in the workplace for example. But the less symmetrical people were no more likely to be jealous in general, he found, than more syrrunetrical folk. *

Girls get competitive, but only if it's worth it

IF YOU'VE always suspected that the male of the species can be competitive to the point of stupidity, here's your proof. Rosanne Roy from McGin University in Montreal and her colleagues have found that boys will compete just for the sake of it, regardless of whether there's anything to be gained. But girls won't waste effort on competition unless it pays. To compare the way the different sexes compete, the team got 4o groups of four boys or four girls, aged 5 to 6 or 9 to 10, to play two specially designed games. In one, for instance, the children had to thread beads on a stick until it was full, taking the beads from either a common pot or another player. One set of rules meant that everyone would eventually win, so competition was pointless. Another set of rules allowed for only one winner, so competing made sense. The girls spent more time watching the reactions of their competitors and responding to them. "They would watch the facial expression of their opponent as they decided whether or not to take the bead. Sometimes they would decide not to," says Roy. And the older girls wasted no effort on competition, except when it paid off. Boys, on the other hand, competed just for the sake of it even if there was nothing to be gained. "It was way too much fun to take from others," Roy says. .

GM comes a cropper

Ian Lowe comments on gene research in the field

IT HASN'T been a good couple of weeks for the proponents of genetically modified (GM) food crops. For starters, studies have surfaced in Europe and the US (New Scientist, 17 August, p ii) which show that GM food crops can interact genetically with weeds. And then yet another mishandled field trial came to light. A team from the Unive rsity of Ulle in France found that GM varieties of sugar beet and their wild relatives regularly swap genes, while a group at Ohio State University found a similar effect in sunflowers. This is not a problem in regions where the only variety of a crop .species is an introduced plant, as with soya in the US. But it is of real concern in countries like the UK, where wild, weedy varieties of sugar beet and oilseed rape (canola) coexist with commercial crops. Also a three-year field trial of GM canola in Britain has been scrapped because the original seed was unwittingly contaminated with antibiotic genes. The company responsible, Aventis CropScience, recognised its mistake and notified the regulatory authority. Not only was the seed it planted not the variety which it had been granted permission to grow, but the inclusion of antibiotic genes raised a possibility of them passing into livestock or humans via the gene swappingprocess. The UK government ruled that the entire crop, on 14 sites spread over eight different counties, will have to be destroyed. Aventis says it is confident there has been no negative impact on biodiversity- But there is understandable concem that the rogue genes could already have spread to wild varieties of oilseed rape growing in hedgerows near the trial plots. These incidents have come at a bad time for companies promoting the cultivation of GM crops. Some European countries, such as Greece and France, are already very hostile to the whole idea. other govem- ments are more sympathetic. British Prime Minister Tony Blair negotiated a deal which delayed commercial planting Until 2003, after extensive field trials. But the recent mixup has meant that those trials have raised the level of public concern, rather than reassuring the community that the benefits of GM crops outweigh the risks.

The UK Minister for the Environ- ment, Food and Rural Affairs, Eliot Morley told the media his government was under "enormous pressure" from the biotech companies, the US government and the World Trade Organisation to allow planting of GM crops. His admission seems to have only strengthened public concern. A fundamental problem remains. The GM crops introduced so far provide no obvious benefits to consumers to justify the risks. So it continues to be unlikely, as newspaper editorials in Britain were saying last week, that GM food products will be widely accepted in Europe. That is certainly a problem for Australian farmers who wish to export into European markets. And it will fuel the contentious political debate that recently was so lively during the New Zealand election.