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Mungo Echoes NS 31 Mar 2001
A MAN who died about 60,000 years ago in Australia may be about to turn our theory of human origins on its head. Researchers in Australia have accomplished the extremely difficult feat of extracting DNA from his skeleton, and were astonished to find that it looks like nothing they have ever seen before. The DNA, which is the oldest ever recovered from human remains, shows that while the man is completely anatomically modem, he came from a genetic lineage that is now extinct. This finding challenges the prevailing theory that all modern humans are descended from a group of people who migrated from Africa around 100,000 years ago. "It's remarkable-totally unpredicted, says anthropologist Alan Mann of the University of Pennsylvania. "What it says is that the more we know [about human origins], the more confusing the picture becomes." Mungo Man's remains were found on the shores of Lake Mungo in south-eastern Australia in 1974. They were originally radiocarbon-dated to about 30,000 years old, but in 1999 a reassessment using three different techniques showed the bones to date from around 60,000 years ago. In 1995, a team led by anthropologist Alan Thorne of the Australian National University in Canberra began an attempt to extract genetic material from the remains. Doctoral student Gregory Adcock and his colleagues at CSIRO Plant Industry managed to replicate and sequence a single gene from Mungo Man's mitochondria, the powerhouses of cells whose small genome is passed down the female line. Simon Easteal, an evolutionary geneticist at ANU, then set about analysing the sequence and comparing it with sequences of the same gene from nine other early Australians-ranging in age from 8000 to 15,000 years-as well as 3453 contemporary people from around the world, chimpanzees, bonobos (pygmy chimps) and two European Neanderthals. Easteal looked for patterns of descent and worked out which "genetic tree" fitted the data best. According to this evolutionary tree, chimps and bonobos were first to branch off the trunk leading to modern people. Neanderthals split off next, then Mungo Man's line and finally the line that led to the most recent common ancestor of contemporary people, including the ancient Australians but excluding Mungo Man. "We can say with a high degree of confidence that modern people arrived in Australia before the new lineage [of the most recent common ancestor] arrived," Easteal says. According to Thorne, the findings-due to be published next week in the online edition of the Proceedings of the National Academy of Sciences-threaten to topple the leading theory of human origins, the "outof-Africa" model. This proposes that all living people are descended from a group of modern Homo sapiens who left Africa roughly 100,000 to 150,000 years ago. Their descendants spread around the world, replacing existing populations of "archaic" people, such as Neanderthals and the more ancient Homo erectus. But if anatomically modem humansfrom a lineage that emerged before the most recent common ancestor of people todaywere living in Australia 60,000 years ago, "a simplistic out-of-Africa model is no longer tenable", says Thome Thorne is one of the founders of the rival "regional continuity" model, which postulates that H. erectus began migrating from Africa over 1.5 million years ago, and from these migrants H. sapiens evolved at the same time in various regions around the world. Those early people remained on the same evolutionary path by sharing their genes through interbreeding. In Thorne's scenario, Mungo Man's ancestors probably evolved in Asia. They gradually migrated to Australia, where the lineage vanished. Because the lineage is based on a single mitochondrial gene, it is too early to know exactly what happened. The clan could have been wiped out by newcomers, or the gene may, for some reason, not have been passed from mother to daughter. That is why out-of-Africa proponents, including ANU physical anthropologist Colin Groves, argue that the new data does not knock their model from the top of the theoretical pile. The genetic evidence is equivocal, he says. "The African-origin model stands or falls by the fossil evidence. In my opinion, it stands." But Groves praises Adcock's technical achievement. Retrieving such old DNA is a "real coup", he says. Leigh Dayton, Sydney
Black Silicon NS 31 Mar 2001
Recently the use of fast pulsed lazers against a silicon wafer in he presence of sulfur hexafluoride has been shown to induce a black surface containing the crystal skeleton etched by fluorine to which sulfur atoms have attached broadening the conduction band so that from the infra-red through the visible, there is up to 97% absorbtion. This is expected to produce up to a doubling of efficiency of silicon solar electric panels and super sensitive video cameras and instruments.
Scrub the planet clean NS 31 Mar 2001
Giant chemical ponds could suck up as much C02 as we produce
IF FORESTS are not sucking up enough carbon dioxide to halt global warming, why not make an artificial "superforest" instead? A team of US government researchers estimate that a superforest which covers 200,000 square kilometres-roughly the size of Minnesota-would absorb CO, as fast as humanity is now churning it out. Most strategies to curb global warming focus on producing less CO,. But Hans Ziock of Los Alamos National Laboratory in New Mexico argues that we need to concentrate more on removing CO, with "scrubbers". Carbon dioxide scrubbers were first suggested as a way of reducing emissions from individual power plants and even vehicles. But installing them would be a huge burden on existing industries. Now Ziock and colleagues Klaus Lackner and Scott Eliott say you don't actually have to build the scrubbers where the CO, is produced. Lackner studied a simple reaction in which a calcium hydroxide solution absorbs dilute CO, from the air. You can then recover the solid calcium carbonate from the scrubber and heat it to extract the CO,. The calcium oxide residue is recycled back into the solution and the pure CO, is reacted with naturally occurring magnesium silicates to form a stable rock-like solid that's easy to dispose of. Ziock reatised that the wind would play a crucial role. "Once every week the wind goes all the way round the Earth, so one can process a large fraction of the atmosphere over the course of a few years." In the lab, the researchers tested how much CO, would be absorbed by a static scrubber with typical winds flowing over it. Based on this data, they estimate that a huge scrubber, essentially a collection of calcium hydroxide ponds with an area of 200,000 square kilometres would remove about 7 gigatonnes of C02 per year-equal to the amount people produce.
The team also calculated that the forest could be a fraction of that size if you draw up more solution and expose more of it to the air using vertical fences with branching features, like windmills or trees. Such str-uctures would be able to absorb 20 to 30 times as much CO, as a regular forest.
Other researchers say the idea compares favourably with other ways of reducing emissions, such as converting electricity production to wind or solar power. "I'm really happy to see some new and clever thinking, " says Jae Edmonds of Pacific Northwest National Laboratory's office in Washington DC. The cost is a worry, says F. Sherwood Rowland of the University of California at Irvine, but "the longer the population keeps releasing CO, directly to the atmosphere, the more likely the answer will require driving levels back down." Eugenie Samuel
More at: Geophysical Research Letters (vol 28, p 1235)
Protests take the shine off golden rice NS 31 Mar 2001
CONTROVERSY continues to surround the development of genetically engineered "golden rice" designed to combat vitamin A deficiency.
After talks with Greenpeace at the headquarters of the International Rice Research Institute in the Philippines last week, IRRI researchers said it would be at least four years before field trials would start. But the Peasant Movement of the Philippines (KMP), a radical group which campaigns against the globalisation of food production and
GM crops, still plans to demonstrate against IRRI next week.
Golden rice is engineered to contain beta-carotene, a precursor of vitamin A. Shortage of the vitamin in food is thought to kill up to 2 million people a year worldwide. IRRI, a publicly funded research body responsible for the creation of high-yield rice varieties, took delivery of samples of golden rice in January, after several companies, including Syngenta Seeds and Monsanto, handed over the rights to its development.
But last week, IRRI played down the seed's potential. "Much work remains to be done to develop golden rice into the successful strategy we feel it can become to help combat vitamin A deficiency," says IRRI director Ronald Cantrell. At the moment, the crop contains only low level,s of beta-carotene, he says. "It will be at least three to four years before there are any field trials and another two years before it may reach farmers."
Greenpeace has said that researchers have failed to look for natural rice varieties that could be interbred with modern strains to provide vitamin A. And it accused the biotech industry of 'using the misery of mothers and children" to gain acceptance for GM crops. But after the meeting, Greenpeace's South-East Asian campaign director Von Hernandez praised IRRI's 'more honest" assessment of the potential of golden rice.
The KMP's leader, Rafael Mariano, says the Philippines' rice industry is In crisis after the liberalisation of trade. 'Golden rice can only make matters worse," he claims. Fred Pearce
Gofta catch them all NS 31 Mar 2001
Europe wants a licence to kill off one of the world's last great fisheries
THE European Union is demanding an increase of up to 60 per cent in the amount of fish its trawlers are allowed to catch off West Africa. Conservation scientists are appalled by the proposals. They say these waters are already seriously overfished, and that such large catches will be unsustainable.
The demand comes as the EU is proposing to drastically cut its fishing fleet to save dwindling fish stocks in the North Sea. Nutrient-rich cold water rises to the surface along 2000 kilometres of the Atlantic coAst from Morocco to Guinea-Bissau, making this one of the world last great fisheries. But since the arrival of foreign trawlers, particularly from the EU, in the past decade, fish stocks have crashed.
"It is clear there is overfishing throughout the region," says Pierre Campredon, a French marine biologist who advises the Mauritanian government on fisheries. 'And there is huge wastage. Shrimp trawlers often throw back more unwanted fish than they catch.' Several hundred trawlers from Spain, the Netherlands, Portugal and other EU nations operate in the zone under licences negotiated between the EU and West African govemments. The three largest licences, covering waters controlled by Mauritania, Senegal and Guinea-Bissau, are up for renewal this year.
Europe is pushing for big increases. In the first negotiations of the year, which continued in Dakar this week, EU negotiators have asked Senegal for a 61 per cent increase in licensed catch from the end of April, according to Senegalese negotiators.
Senegal's fish stocks are 'at a critical moment" says Amadou Wade of Fenagie Peche, the country's fisheries federation. 'There is pillage, both by Senegalese and foreign boats." Foreign trawlers, dominated by the EU, take 100,000 tonnes of fish from Senegalese waters each year, Wade says. The negotiations with Senegal are likely to set a precedent for talks in the coming weeks with its neighbour Mauritania, which has the richest fishing grounds in the region.
West African governments feel under pressure to oblige the EU, says Campredon. 'These countries have large debts. They say they cannot refuse the EU for that reason." Wade, one of Sengal's negotiators, says that "the EU could refuse to let us have access to its markets for trade if we don't comply'. . The revelations come at an embarrassing time for the EU, which has a policy of supporting sustainable fisheries. Last week, the European Commission announced plans to cut the EU fleet by 40 per cent and radically overhaul its fisheries policy, including its negotiations with foreign governments. Otherwise, it warned, 'the status of the Community as a responsible international player will be undermined".
EU fisheries spokesman Gregor Kreuzhuber this week refused to discuss the detail of the negotiations. "The Commission hasn't formally mentioned figures," he said. 'Any final agreement will be subject to an assessment of the resources." Fred Pearce, Dakar
The first split second Govert Schilling NS 30 Mar 2001
During inflation pwerful gravitational waves should have been wrenched into existence. Just tlike the density fluctuations that got blown up into galaxy seeds, other kinds of wrinkles in space-time were inflated into travelling waves.
Gravitational waves would have passed unaffected through the primal fireball so they would be carrying a signal from the dawn of time. Some peculiar instruments are being built to detect these but we are more likely to detect them from their foot prints faint marks on the surface of the primordial fireball.
When the atoms of hydrogen first formed the photons which had been bouncing in the plasma headed off into space stretched from a brilliant hot gas by the expansion of the universe all
that's left is a very faint microwave glow known as the cosmic microwave background (CMB). This primordial radiation was discovered in 1965.
There are tiny differences in the brightness or temperature of the CMB between different parts of the sky. These were seen by NASA!s Cosmic Background Explorer satellite (COBE) in the early 1990s, and have been studied in much more detail by balloon experiments like Boomerang and MAXIMA (Ne,w Scientist, 16 December 2000, p 26).
Some of this variation traces the slight density fluctuations in the early Universe, and some of it comes from Doppler shifts produced by moving gas. Giant sound waves propagated through the blazing hot matter, compressing and diluting it, and as gravitational waves warp whatever they pass though, they must also have squeezed and stretched the primeval fireball. Unfortunately, no matter how accurate the measurements of brightness, cosmologists will never be able to tell one contribution from another, so it's not possible to separate the effect of primordial, inflationary gravitational waves from the real density enhancements or from the effect of sound waves.
Luckily there is a subtler message in the microwaves: polarisation. Each microwave photon vibrates in a particular directionits plane of polarisation. Usually, each photon is polarised in a different, random direction, but when ionised matter is moving it imposes an overall direction of polarisation on the radiation it scatters.
And crucially, gravitational waves generate a distinctive type of polarisation, unlike the patterns made by density changes and sound waves. If you measure the polarisation direction for every part of the sky, and draw a short line in that direction at each particular spot, what you get looks a bit like a map of wind velocities on Earth. Gravitational waves create swirl-like patterns, unlike any other phenomenon. To see these patterns, what we need is the microwave equivalent of Polaroid sunglasses. A set of parallel wires will stop waves with one polarisation while letting others pass. By rotating this set-up and measuring how much radiation leaks through, you can work out the polarisation. caught the thief? Not yet. The will probably be very weak, so highly accurate measurements ightness of the background to iable signal. ew balloon-borne and ground based instruments stand a chance. At the South Pole, DASI (Degree Angular Scale Interferometer) combines signals from 13 telescopes, making it a sensitive and high-resolution instrument. John Carlstrom, an astrophysicist at the University of Chicago, thinks it might be the first to catch CMB polarisation. Meanwhile, Fred Lo of the Academia Sinica in Taipei, Taiwan, is in charge of AMIBA (Array for Microwave Background Anisotropy), a large, sensitive 19-element interferometer due to be built in 2004, either at Mauna Kea, Hawaii, or in Chile. And two balloon-borne experiments that hit the headlines last year with their detailed measurements of the microwave background will fly again later this year: MAXIMA this spring, and Boomerang in December. Jeff Peterson of Carnegie Mellon University in Pittsburgh, Pennsylvania, expects one of these instruments to detect CMB polarisation within the next three years. And the highly sensitive European Planck satellite, which will be launched in 2007, will almost certainly see it. Because gravitational waves contribute only a small part of the total polarisation, even Planck probably won't be able to extract the gravitational inflationary signal. "I'd bet my money on post-Planck missions," says Robert Caldwell of Dartmouth College in Hanover, New Hampshire. It will probably be another decade or so before the weak polarisation signal from primordial gravitational waves can be tracked down. So the challenges are great. But then, the stakes are high. From the polarisation data, it should be possible to deduce the strength of the gravitational waves. This, in turn, tells you when inflation took place. The earlier inflation started off, the more violent the expansion, and so the stronger the gravitational waves are expected to be.
And if we know when it happened, we might find out why. It was once thought that inflation took place 10-31 to 10-31 seconds from time zero, according to Caldwell, when an original cosmic superforce split into three independent forces: the strong and weak nuclear forces, and the electromagnetic force. This force splitting happens when space goes through a phase transition, like the transition from liquid water to ice. The energy released by the phase transition is what drives inflation.
But there is no definitive theory of how the three forces come to be unified only a slew of tentative 'grand unified theories". So there's plenty of uncertainty as to when and why the forces split in the early Universe. Some theories say there are extra, hidden dimensions to space. If these extra dimensions are as large as a fair fraction of a millimetre, inflation might have occurred as late as 10-14 seconds after time zero. 'But,' says Caldwell, 'this is a rock bottom latest time."
Finding the gravitational wave spectrum would knock out many of the dozens of inflation models thought up by creative theorists. "Right now," says Bram Achterberg of Utrecht University in the Netherlands, "no single model seems to be more plausible than any other, but from the gravitational wave spectrum it would be possible to disprove some of them."
So studying the gravitational wave spectrum would be a powerful way of probing extremely high energies, and examining theories that describe the true fundamental structure of matter. Physicists may never be able to build accelerators powerful enough to reach the high energies experienced at the start of the Universe, so tracing inflation may be the only way to do it.
Then again, we might find a spectrum that can't be explained by inflation at all. The theorists would have to start from scratch. Nobody really knows what was going on in that first split second, which is why a signal from the big bang would be so important.
It's not a sure thing, however. "If inflation took place at a low energy scale, the gravitational wave signal will be too small to be detected," says Peterson. This would not disprove inflation, but it would extinguish any hope of looking beyond the microwave background to the beginning of time.
GRAVITATIONAL waves from the beginning of time may be constantly passing through the Earth, stretching and ftexing everything they meet. But how can we detect them? A pair of huge devices called UGO (Loser lnterforonieter Gravitational Wave Observatory) Is being built In Louisiana and In Washington State. Each one will use laser beams to monitor distances Inside two 4-kilometre-long tunnels, which should vary when a gravity wave passes through. LIGO is the star among the new generation of gravitational wave detectors-but It's not sensitive to the very-low-frequency waves that are expected to come from the big bang. Moreover, the amplitude of these waves Is probably too small to be measured by LIGO, even if It were sensitive to the frequency. The planned space-based detector called LISA (Laser Interferometer Space Antenna), due to be launched In 20IO, samples lower frequency waves, but it too will probably not be sensitive enough to pick up the feeble prlrnordial waves.
Then agaln, although most theories do not predict high-frequency, short wavelength gravitational waves, very little Is really known about what happened less than a quadrillionth of a quadrillionth of a second after time zero. There's at least one model, by Massimo Giovannini of Tufts University in Medfbrd, Massachusetts, that has large amounts of gravitational waves with frequencies of many gigahertz coming from an earlier expansion phase, after lnflation. At the University of Birmingham, Mike Cruise has a prototype detector for these high ency waves. A gravitational wave can induce a tiny rotation of the plane in which an electromagnetic wave moves. SO Cruise and his colleagues are pumping microwaves around a circular copper wave guide to try to amplify this effect to measurable proportions. 'It's still many orders of magnitude less sensitlve than what we ultimately need,' he says, 'but in the next couple of years, we hope to make real technical progress.
Govert Schitiing is a science writer based in Utrecht, the Netherlands
Further reading: The Inflationary Universe: The Quest for a New Theory of Cosmic Origins by Alan H. Guth (Helix Books, 1998) Catch the wave
Just a Youngster NS 13 Jan 2001
EARTH is probably a youngster among planets of its kind, says an astronomer in Australia. This may mean that any intelligent beings that have evolved on other Earth-like planets will be so highly advanced that to them we seem little better than bacteria. No wonder they haven't been in touch yet. Charles Lineweaver of the University of New South Wales in Sydney says that Earth-like planets orbiting other stars will be on average about 1.8 bilhon years older than Earth. He deduced this figure by cleverly combining a host of factors that determine the formatim and destruction of terrestrial planets. One such factor is the way in which heavy atoms such as iron have become more plentiful since the big bang. The early Universe contained only the lightweight elements hydrogen and hehum. All other atoms were made in the thermonuclear fumaces of stars, and elements heavier than iron are only released into interstellar space when old, massive stars explode as supemovas. Rocky planets cannot form around a star unless there are enough heavy atoms in the dust it is made of, so there were none when the Universe was young. However, a brew too rich in heavy elements would lead to "hot jupiters"@ant planets orbiting so close to their parent stars that they destroy newbom earths. a paper submitted to the journal Icarus, Lineweaver concludes that three-quarters of all Earth-hke planets must have been around longer than the Earth and that the average age is 6.4 bilhon years, compared with Earth's 4.6 billion years. "This analysis gives us an age distribution for hfe on such planets and a rare clue about how we compare to other hfe which may inhabit the Universe," he says. But neither Lineweaver nor anyone else will commit themselves on what this tells us about the prospects of finding ETs. "The odds against simple life are still completely uncertain," says Martin Rees of the University of Cambridge. "We don't know the chance of any extraterrestrial intelligence evolving anywhere, nor what variety of evolutionary tracks are possible." However, Lineweaver's calculations could offer a hint about why we haven't picked up any radio signals from alien beings. Intelligent life on older planets may have advanced as far beyond us as we are beyond bacteria, and such beings would be unlikely to communicate via a medium as primitive as radio waves. "Certainly this can be a way of explaining the 'Great Silence'," says ET hunter Paul Schuch, executive director of the SETI League in New Jersey. "But I rather think our lack of success is more related to the fact that, on the cosmic clock, we just started looking yesterday. These things take time, and require great patience." Marcus Chown
More at: xxx.lani.gov (Astrophysics e-print 0012399)
Just when you thought it was safe to stop evolving, culture and technology may be itching to wipe out your genes. Is human evolution about to take off, asks Philip Cohen
The Future of Human Evolution NS 13 Jan 2001
IT'S THE ultimate problem in family etiquette. The researchers from your local lab phone to say they've thawed out a 50,000-year-old ancestor of yours, and they want to bring him over. The question is, should you welcome this forebear into your home? Perhaps, like palaeobiologist Simon Conway Morris of Cambridge University, you believe that we differ very little from people who lived tens of millennia before us. He suggests that, given suitable education, your long-lost kin would have no problem holding their own in your business or at your local bistro. "They could walk into the room and, given a haircut, they'd fit right in," says Conway Morris. In other words, our evolution has been all but over for quite some time. There is a certain comfort in that thought. After all, if you decide to go for cryogenic preservation when you die, it could be you who's cast in the role of the defrosted dinner guest. But before you make those hotel reservations for a family reunion in 50,000 years' time, you should be wamed that there are those who strongly disagree with Conway Morris's forecast for our species. Far from slowing evolution down, they say, technology and culture could be accelerating it to a furious pace. So instead of being welcomed as an equal, you could be shunned as a primitive freak. Despite their varying visions of our future, scientists on all sides of the debate over our evolutionary destiny agree about how things started out. In the beginning, all life on Earth was at the mercy of the same evolutionary forces of natural selection. Competition, starvation, predators, disease and sometimes bad luck took their toll on our ancestors and thereby pushed and pulled the gene pool in different directions. Overall, those with genes that suited the environment survived and reproduced, while those with an inappropriate genetic constitution disappeared into oblivion. Then, about 5 million years ago, primate evolution split along two tracks: one leading towards humans, the other towards chimpanzees. A million years later, our ancestors adopted an upright gait, and 2 million years after that their bodies and brains began to grow and they started making primitive stone tools. The first modem-looking humans appear in the fossil record about 130,000 years ago. By 50,000 years ago, there is evidence for folks who appear to have distinctly modem bodies and lifestyles. They created complex tools and jewellery, built shelters, buried their dead in graves and probably had the language skills to chat about what they were doing. And through these simple acts, the newly minted Homo sapiens unintentionally thwarted the very forces that had created our species, says Conway Morris. Effective weapons removed most of the threat of predators, and agricultural development beat back starvation. "The technological innovations that took place during this period were astounding," he says. 'But there is no sign that this was due to genetic changes." And while we still haven't banished human hunger or disease from the planet, the trend is clear. We are cushioning ourselves from the forces that shaped our biology for aeons. Steve Jones, a geneticist at University College London and author of The Language of Genes, agrees. Culture and technology, he says, spelled the beginning of the end for evolution in its classic sense-natural selecfion of genes better suited to their environment. In the developed world, child mortality has declined drastically and family size tends to be small. Put simply, natural selection doesn't take place if everyone, regardless of the genes they carry, has two children who survive to reproduce.
Too much alike
And this is only half the story, Jones adds. For evolution to proceed, there must not only be environmental rigours that weed out the weakest, there must also be genetic variation between members of the population so that some are better suited to cope than others. Humans, it turns out, are already remarkably similar at the genetic level. There is only about a 0.1 per cent difference between your DNA and that of any passerby hi contrast, among our close relatives the chimpanzees, the variafion is at least five times that. Jones believes that modem life continues to chip away at the few remaining differences. For instance, mutations in the chromosomes of eggs or sperm become more common as parents age, but this source of genetic variation is disappearing because parental age is decreasing as couples tend to stop at two kids. What's more, in the past, some human mutations were preserved because they provided protection from disease. But as public health measures eliminate deaths from these diseases, the number of people who carry the mutation decreases. All the while, says Jones, our knack for buflding machines that whisk us around the planet dashes any hope that@ we might spin off a new species of human. That's because the spawning of new species requires reproducfive isolation, and geographic barriers often provide just the right type of genetic privacy. But our wanderlust regularly gives the gene pool a good, homogenising stir. With mutational fuel running low and the engine of natural selection idling, Jones concludes that our evolution is, at most, coasting slowly to a standstill. But according to Lynn Jorde, a human geneticist at the University of Utah, it is just changing direction. Agricultural developments may have made famine less frequent, he points out, but they have also caused people to five in larger, more densely populated areas, increasing the likelihood and impact of epidemics such as cholera and AIDS. In addition, our frequent globetrotting has allowed disease organisms to hitch rides into even the most remote corrununines. "All this presented our immune systems with greater challenges," he says. Science may have spawned medicine, but it has also unleashed an industrial and technological revolution that spews out radioactivity and chemicals that can contribute to an increase in our mutation rate-or act directly as selective forces. "A thousand people a day die of cigarette smoking in the US alone," says Jorde. "That's got to have some impact." Even a little impact, genetically speaking, could go a long way. Remember that the vast difference between us and chimps comes down to a mere 1.5 per cent difference in our DNA. In fact, our current genetic variability is still high enough to pose a significant medical problem. Genetic factors mean that new drugs often prove ineffective on a significant chunk of the population (New Scientist, 4 November 2000, p 31). Still, we may ultimately manage to thwart the health and pollution problems of our own making. So would that lead to human evolution's last breath? Christopher Wills of the University of Cahfomia in San Diego certainly doesn't think so. He believes that as the deadly blows of past selective pressures disappeared, we began to be shaped by more subtle but equally persuasive forces. "It is less obvious. But you don't have to pile up bodies in the street to have evolution." In fact, he believes that rather than slowing us down, our culture has probably propelled us into developing at unprecedented speeds. Culture itself shapes our genes. In those societies where milk drinking is an ancient pracfice, for example, people have genes that allow them to digest the milk sugar lactose. People whose ancestors were not milk-drinkers tend to lack these mutations. Wills argues that today's globalisation increases the potential diversity of the human gene pool by bringing together such specialised versions of genes that had been separated through much of history. "This creates new combinations that may never have been seen before," he says. In his book Children of Prometheus, Wills argues that the major evolutionary influence of culture is to create new environments and select for human generic diversity. Fine motor skills, for instance, were probably not much use when our ancestors were doing little more technical than smashing rocks. But in a more modern society you can benefit from both big muscles, and the delicate manipulations of a watchmaker. One talent of the human animal is to devise ever more exacting mental and physical challenges. Wills cites the recent rise in popularity of extreme sports. "These people are now succeeding based on skills that didn't exist even a few years ago," he says. He also points out that diversity itself can be selected for. Outside our species, for example, researchers have found that trees that are rare in forests reproduce more often than more common varieties. The thinking is that a sparse population gives species-specific parasites less of a chance to breed. Similarly, he argues that tare traits are rewarded in our culture. Musical geniuses thrive exactly because they are exceptional. If we all had perfect pitch and virtuosity, we would clearly be less impressed. It is in intellectual and psychological areas that our culture generates the greatest advancement and diversity, according to Wills. The decision not to have children, for example, has exactly the same evolutionary impact as losing a child through predation or disease. Now consider that this form of selection might be triggered by our genetic constitution. Wills points out that people who cope badly with stress in their lives often choose not to have children, so the effect may be a bloodless coup where those genes that allow us to deal with the stresses of modem life emerge victorious. Jorde agrees that the evolution of the brain is a neglected area. "The best new estimates say a third or more of our genes play a role in the development or function of our brain. We're only just beginning to understand what that means for our evolution," he says. The dystrophin muscle gene, for example, which causes muscular dystrophy wheh faulty, is also expressed in the brain. So too are XRCC4 and Lig IV, which are involved in immunity. As a result, genetic changes that have improved muscle tone or our ability to fight disease could have had psychological or intellectual repercussions.
All this suggests that it would take a lot more than a haircut to bring our primitive ancestors up to scratch. They may have been mentally incapable oi dealing with modem society. But it isn't always obvious how to chart the effects of culture on evolution. Do increases in the use of birth control select for better parents, because only those that really want children tend to have them? Or does it mean that a great many more children are bom to parents who mess up their use of pills or condoms, selecfing for parents who are less than careful? Richard Dawkins of Oxford University questions whether a good case can be made for close co-evolution of human genes and culture. He points out that much cultural change is simply too fast and too fickle. It takes a reproductive generation, say 25 years, for a slight change in the human gene pool to emerge, while fashions change almost daily. Dawkins says that if the human gene pool were a cork thrown into the ocean, then most cultural effects would be like chaofic winds tossing it back and forth, without tugging it in any particular direction. Yet, continuing the metaphor, Dawkins admits there might be what he calls "Guff Stream effects"-long-term trends within society that draw our species in a particular direction. One of his nominees for such a deep cultural current is the growth of computational power. The density of transistors on computer chips has doubled on average every 18 months since the integrated circuit was invented, a phenomenon known as Moore's law. Of course, this would influence human evolution only if the ability to cope with this electronic explosion provides some reproductive advantage. Is that so crazy? The Intemet has spawned a whole generation whose social interaction is increasingly electronic. Chances are that some readers of this feature will know couples who forged e-relationships that have blossomed into e-marriages. And technology's influence on mating choice extends beyond the Intemet's great cyber-singles bar. Recently, researchers from the University of Liverpool reported that young men in pubs and bars use their mobile phones as lekking devices, meeting in groups and displaying their technology as a symbol of status and wealth, in much the same way that male grouse congregate and show off to attract mates (Human Nature, vol 11, p 93). Whether or not culture has shaped our biology in the past, John Campbell of the University of California, Los Angeles, thinks we will soon consciously control our own evolution. At a conference two years ago called Engineering the Human Germline, which he helped organise, most experts agreed that the first humans with designer genes will probably be born in the next two decades (New Scientist, 3 October 1998, p 24). 'It will start in the areas that are least controversial, such as treating genetic disease," says Campbell. "But people will soon be dumbfounded by the possibilities." For instance, certain fairly simple natural genetic mutations are now thought to confer resistance to HIV or protection from high diolesterol. And researchers are already hot on the trail of genes that might enhance longevity and cognifive ability. Engineering these refinements into human chromosomes would involve standard genetic manipulations of single human cells and then using these cells to create a clone-the same technology that made Dolly the sheep possible.
The chosen people
Though no one has yet crossed the line and grown genetically engineered human dones, the prospect seems closer flian ever. Doily was a relatively new phenomenon two years ago, but now she is just one of dozens of sheep, mice, coxvs, goats and pigs rolling off the cloning production line. And only a few months ago, a couple from Colorado caused an uproar by using genetic tests to choose an embryo. They wanted a baby that would be a close tissue match for their other daughter, who suffers from an inherited blood disease. Some ethicists saw the episode as the slippery slope towards fun-scale eugenics. If parents are already willing to use genetic screening to create tissue donors, will it be long before they begin to screen for babies with high IQ or superior athletic ability? While many people recoil at the idea of "designer babies", Campbell thinks that small groups are bound to use the latest reproductive techniques to push the boundaries of human evolution. "The technology is going to advance beyond what our conservative society will embrace," he says. "But I think we will see some people evolve at rates we haven't even imagined yet." Geneticist Lee Silver of Princeton University predicts a similar cottage industry of human evolution in his book Remaking Eden. He speculates that cloning and other genetic technologies could create a genetic elite, or what he dubs the "GenRich" class, who would refuse to mate with "natural' human beings and ultimately become a separate species. But Jones doubts that even conscious effort could get us out of our evolutionary rut. The GenRich would be hard pressed to keep their new genes to themselves, he says. History shows that even in a highly stratified society, the classes still mingle due to our basic, animal instincts. "I believe in the healing power of lust," Jones says. And a few improved genes among the 100,000 we possess, in a global population of 6 billion, is a drop in the ocean. But even if Jones is right and there is no way on Earth that a new humanoid species could arise, engineer Robert Zubrin is betting it will anyway. Zubrin, who is president of Pioneer Astronautics in Colorado, thinks it will happen on another planet. He points out that the very factors which Conway Morris and Jones believe have led to a lull in human evolution-jet travel, light speed communication and advanced medicine-have made it possible for us to venture into space. "Some argue that this means we are at the end of the history of humanity," says Zubrin. "But I think that means we are at our first moments." Our destiny, says Zubrin, is to leave the planet, just as our ancestors left Africa and colonised the rest of the world. And our first stop could be Mars, which might be made habitable through terraforming. In fact, he believes that a fully functional Martian city with hundreds of residents will be built in this century. And as surely as our descendants shape that world, it will shape them. There would be incredible selection for people whose genes help them survive in the harsh environment, and even on a terraformed Mars this would long persist. While providing Earthly [email protected] with genetic enhancements may seem like a frivolity, it would just be good sense to endow Martian kids with the ability to endure a thinner atmosphere and stronger solar radiation. And since the gravity on Mars is only about one-third the strength of Earth's, Zubrin suggests it might also be wise to give its inhabitants long, springy legs to cover terrain more easily. The unprecedented geographic isolation of this new civilisation and the speed of genetic selection among its inhabitants would make it fertile ground on which a new species could arise. While it might not be that surprising that a rocket scientist such as Zubrin envisages a future in space, some biologists are quick to agree with him. "If we find even a distant planet that can support life, nothing will stop us from getting there one way or another," says Wills. "That's because our curiosity is orders of magnitude above that of other species." . Perhaps that's why you can't help wondering what you should bring for that family dinner party in the year 52,000. It might be wise to hedge your bets. A good bottle of wine for the parents, perhaps, and extremely long elastic trousers for the kids.
Unleash the bugs of war NS 12 May 2001
The US looks set to scupper talks on enforcing the bioweapons treaty
THE Bush administration is on the brink of demolishing another international armscontrol agreement. In Geneva this week, SO nations are trying to finalise a mechanism for policing the 1972 treaty banning biological weapons. The US is widely thought to have decided to reject the protocol, which will collapse without its support.
But surprisingly, some arms control experts who support a stronger bioweapons treaty say this could be a good thing. They argue that the current proposal is so weak that it could help rather than hinder would-be biowarriors. Others say the proposal must succeed, because governments are unlikely ever to negotiate a stronger one. Negotiations on the protocol began in 199S, after the exposure of bioweapons programmes in Iraq and Russia made it clear the Biological Weapons Convention needed teeth. The compromise proposal on the table in Geneva this week calls on countries to declare what biological defence facilities and high-containment laboratories they possess, as well the agents they work with. A limited number of random inspections of these facilities would then be made by a proposed Organisation for the Prohibition of Biological Weapons, to check the declarations. Stricter inspections could be made if a government suspects it has been attacked, or that another country has bioweapons-so long as other member states agree. The US has been unenthusiastic about random visits ever since talks began (New Scientist, 28 February 1998, p 16). Drugs companies say they could endanger commercial secrets. The US delegation in Geneva this week has said only that it is waiting for the Bush administration to decide its policy.
But arms-control experts say the Bush team has already decided to reject the protocol. "There are indications that it would prefer that the concept either be radically reshaped, or simply allowed to wither away," writes,james Leonard, former US ambassador to the UN Conference on Disarmament, in this month's Artns Control Today. "The new administration will almost certainly reject the current proposal," says Alan Zelicoff of Sandia National Laboratories in New Mexico, a US negotiator until 1999. "And the
Senate is unlikely to approve it in any case.' But they and others attribute this not to the current administration's distaste for arms control, but to the proposal's weakness. For example, states bent on cheating could simply not declare labs, or they could grow pathogens in breweries (which need not be declared) or antibiotics factories (which are exempt from visits). Countries get two weeks' warning of random inspections, can limit what the visitors see, censor their report and ban biological sampling.
Even following accusations of breaches of the treaty, the accused still gets 108 hours' notice of an inspection-more than enough to move or conceal cultures and equipment. Countries can also deny access to facilities and prohibit sampling. In a report released in Geneva this week by the Stimson Center, an arms-control think tank in Washington DC, a panel of American scientists and arms inspectors conclude that more research into how to carry out inspections is needed. In a test organised by the Stimson Center last july, two prominent infectious-disease experts, both veterans of bioweapons inspections in Iraq and Russia, visited a high-containment laboratory in New York state. The centre had secretly planted fake anthrax cultures and records, and told the chief technician to "act nervous". The team missed the "anthrax"-but did find several spurious causes for concem.
Critics say this shows the proposed protocol could create unwarranted suspicion instead of greater trust-alienating participants while failing to catch culprits. "An impotent monitoring protocol will implode sooner or later," the Stimson report concludes, which means the bioweapons treaty could be "Violated at will and possibly with impunity".
The question is what will happen if, as seems likely, the US rejects the current proposal. Developing countries and Russia will not sign unless the US does. Europe, which supports the protocol, could try to prolong the current negotiations while trying to bring the US back in. But the US could instead seek to have the talks restarted from scratch, in an attempt to get a different kind of protocol.
Oliver Meier of Vertic, a think tank in London, says that would be the worst outcome. "The current proposal is weak, but if it is made flexible enough, it can evolve. In the current political climate we are unlikely to get a mandate to discuss a stronger agreement. And we can't wait another six years."
The agonising choice now is between a treaty that will do little to stop biowarriors, or nothing at all. Debora MacKenzie
Banished forever NS 12 May 2001
Puny planets like our's get flung into deep space by their big brothers
GIANT planets in faraway solar systems are .marching in towards their parent stars, and banishing small planets like Earth into outer space in the process. That's the conclusion of astronomers in Canada who think they know why these giant planets end up so close to their host stars. Around 60 extrasolar planets have been discovered so far. Most are gas giants several times the size of Jupiter and orbiting very close to their parent stars.
This has baffled astronomers because giant planets in our own Solar System formed in the cold outer regions and have not shifted inwards from their birthplace. Jupiter is about five times as far away from the Sun as the Earth is, but in other solar systems giant planets are sometimes closer to their star than Mercury.
One possibility was that the extrasolar giants also formed in the outer regions of their systems, but lost energy and gravitated towards their stars when loose gas rubbed against them. However, this would leave them in small circular orbits. Instead, these giants seem to have very elongated or .eccentric" orbits.
Now Norman Murray of Toronto University and his team say small planets like Earth or Mars could explain the giants' close orbits. They considered a system in which an outer giant planet completes one orbit in the time it takes a closer small planet to orbit twice. They found that the effect of the two planets periodically lining up is enough to force other small planets in the system into eccentric orbits.
Eventually the orbits of the small planets become so wild that they either swing out into space forever or fall in towards the star. At the same time, the giant planet soaks up extra angular momentum and shifts into a tighter, more eccentric orbit. "This mechanism is robust and can operate in real physical systems," says Eric Ford, who studies giant planet behaviour at Princeton University in New Jersey.
A team led by Garik Israelian at the Astrophysics Institute of the Canary Islands has found something similar happening in a system with at least two extrasolar planets. The star's atmosphere contains lithium-6, which is found in planets but only survives in a star for a few million years (Nature, vol 41 1, p 163). This suggests a giant planet sent its smaller companions careering into the star relatively recently. "You don't want to be around when that giant planet gets moving,' says Murray.
But why haven't the giant planets in our Solar System turfed their weedy companions out into space? Murray suspects it's because there aren't many small planets inside Jupiter's orbit, which means the process would take a very long time-longer than the time the Sun will take to blow up into a red giant near the end of its life. "So I wouldn't worry about it," he says.
Eugenie Samuel, Boston More at: http://arXivorg/abs/astro-ph/0104475
So what's the score? NS 12 May
We humans may have thousands more genes than the genome sequencers have led us to believe
"ONE giant leap for humility". "We're noth ing special". "Scientists find only half as many genes as expected". These are some of the headlines that appeared after papers on the draft genome were published in February. Both the public and private projects esti mated we had just 30,000 to 40,000 genes, far fewer than most previous figures sug gested-and barely more than worms. But the low estimates have ignited a firestorm of controversy. William Haseltine, head of biotech company Human Genome Sciences (HGS) in Rockville, Maryland, has been the most outspoken critic, attacking both the quality of the draft sequences and the gene-finding efforts of those who com piled them. "They're reading smudged text through foggy glasses," he recently snarled. Hasettine claims to have found more than 90,000 genes, while companies such as Affymetrix sell gene chips based on more than 60,000 genes and DoubleTwist puts the number above 65,000. But Craig Venter, head of Celera Genomics, the private rival to the public genome con sortium, is standing by the lower estimate.
He calls it a "truth serum' for his competitors. So are these companies wasting hundreds of millions of dollars on a wild goose chase? Or could the public consortium and Celera end up delaying the development of medical tests and treatments by denying the existence of large numbers of genes? The accuracy of the draft genome is not the issue. The controversy is about how you find the fragmented parts of the genome that actually code for proteins. There are 26,000 genes that researchers more or less agree on. In the papers in Nature and Science (Ne,w Scientist, 17 February, p 4), the public consortium and Celera estimated that there are about another 10,000, based on computer programs that search raw sequences for stretches that resemble known genes.
But the programs tend to throw up lots of genes that don't really exist. To avoid counting these, Celera and the consortium demanded evidence that gene candidates really are transcribed to make the messenger RNAs that cells use to make proteins. "But we only have transcription evidence for half the genes in the body," admits geneticist Michael Zhang at Cold Spring Harbor Laboratory in New York. That's where HGS and similar genome companies come in. Instead of looking at the iaw sequence, they find genes by combing thousands of different cells for bits of mRNA. These are then turned into bits of DNA called expressed sequence tags, or ESTS. Haseltine claims his ESTs provide evidence for more than 10,000 genes that aren't in the consortium's database. 'We have made functional proteins, some of which we are developing as drugs, that are not annotated as even existing in that text," he says. But Celera and the consortium claim their estimates include these proteins. Another problem with gene-finding programs is that they can only look for code that resembles known genes. So they not only turn up candidate genes that don't really exist, they also miss lots of real genes. "Historically, gene-prediction programs have tended to miss over 50 per cent of genes," says geneticist Michael Snyder of Yale University. A group at Ohio State University in Columbus has analysed the same data that the consortium looked at and estimates there are actually about 80,000 genes. In an as yet unpublishe paper, it claims that the consortium's software has missed nearly 850,000 gene segments for which there is protein or RNA evidence. While the debate should be settled eventually, the uncertainty could have far-ranging implications. Some fear that undiscovered genes-and thus potential drug targetscould fall through the cracks. While many labs continue to mine the genome for new genes, some are finding it difficult to get funding. The head of one biomedical research lab, who preferred not to be named, says his funders recently asked him why he was continuing to look for genes when the "genome was finished". "People should not give up the gene count," warns Haseltine. Meanwhile, the rival parties are heading for a showdown. "There's a simple way to settle the question," says Eric Lander of the Whitehead Institute, one of the leaders of the consortium. "Let's randomly select 3 per cent of the genome, have everyone declare the genes that they believe to be in that region, and test the proposed genes.' Let the games begin. Eli Kintisch, Washington DC May 2001 o New Scientist www.newscientist.com