Archive for October, 2008

Swimming, walking salamander robot reconstructs invasion of land

By Ed Yong | October 20, 2008 10:00 am

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Blogging on Peer-Reviewed ResearchMoving robots are becoming more and more advanced, from Honda’s astronaut-like Asimo to the dancing Robo Sapien, a perennial favourite of Christmas stockings. But these advances are still fairly superficial. Most robots still move using pre-defined programmes and making a single robot switch between very different movements, such as walking or swimming, is very difficult. Each movement type would require significant programming effort.

a_badertscher_robot_beach1.jpgRobotics engineers are now looking to nature for inspiration. Animals, of course, are capable of a multitude of different styles of movement. They have been smoothly switching from swimming to walking for hundreds of millions of years, when our distant ancestors first invaded the land from the sea.

This ancient pioneer probably looked a fair bit like the salamanders of today’s rivers and ponds. On the land, modern salamanders walk by stepping forward with diagonally opposite pairs of legs, while its body sways about its hips and shoulders. In the water, they use a different tactic. Their limbs fold back and they swim by rapidly sending S-like waves down their bodies.

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Impulsive minds are primed for drug addiction

By Ed Yong | October 19, 2008 10:00 am

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Blogging on Peer-Reviewed ResearchWe’ve all acted impulsively before, and we have the horrendous clothes, echoing bank accounts and hilarious memories to show for it. But science is beginning to show that impulsive people may be particularly vulnerable to drug addiction, and there is little funny or harmless about that.

img_0046_o.jpgAccording to Government statistics, half a million people in the UK are addicted to class A drugs like cocaine, heroin and amphetamines. All too often, drug addiction and other compulsive disorders like obesity are dismissed as issues of ‘willpower’ and those who succumb to temptation are labelled as ‘weak’. But this attitude is, at best, wrong and, at worst, stigmatising and self-righteous. And it provides no clues for ways of helping people with these problems.

In fact, the evidence suggests that drug addiction is linked to certain personality traits. Being impulsive is one of them, and a tendency to seek out new sensations (often described as “living life to the full”) is another. But do these traits drive people towards drug addiction, or are they a result of the drugs themselves?

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Viruses evolve to be more infectious in well-connected populations

By Ed Yong | October 18, 2008 10:00 am

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Blogging on Peer-Reviewed ResearchA virus, like any other carrier of genetic information, can only enjoy evolutionary success by ensuring that its genetic material is passed on through the ages, and it can only do that if its offspring finds new hosts to infect. Its host must live to infect again, and the virus that kills its host prematurely signs its own evolutionary death sentence.

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So over time, we might expect that the ideal virus would evolve to never kill any of its hosts – it would have zero ‘virulence’. It would also evolve to successfully infect every host it comes into contact with it – it would have a hundred per cent ‘infectivity’. In this way, a virus would turn any hosts it meets into long-lived virus factories.

But this expectation is based on a model with overly simple assumptions. It only holds true if the virus’s potential hosts are evenly-distributed and ignores questions of distance. In this artificial scenario, once one person in a population carries the virus, every other person has an equal chance of being infected. Obviously, this is not the case – humans, for example, are concentrated in certain areas, be they villages or cities. And even highly infective viruses can only be spread to new hosts within easy reach.

In this more realistic world, highly infective viruses would soon infect every possible host in the local area, exhausting themselves of potential carriers. Strains that were less infective would then gain an advantage. On the face of it, this model makes sense, but testing it can be difficult. Needless to say, ethics committees might frown upon infecting people with viruses and constraining them to different locations to see what happens. Insects are another rmatter.

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CATEGORIZED UNDER: Evolution, Viruses

The chimpanzee Stone Age

By Ed Yong | October 17, 2008 10:07 am

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Blogging on Peer-Reviewed ResearchIn the Ivory Coast, a small stream called Audrenisrou winds its way through the lowland rainforest of the Tai National Park. On the floodplain of this stream, at a site called Nuolo, lie several stones that seem unassuming at first glance. But to the trained eye, they are a window to the past.

zyon2.jpgTheir shape is different to other stones that have been worn away by natural erosion. They have been flaked in systematic ways and many are flattened and sharp. Clearly, they were shaped by hand for a purpose – they are tools. Their creators were not humans, but close relatives who lived in these rainforests thousands of years ago – the ancestors of modern chimpanzees.

The Nuolo stones were uncovered by Julio Mercader form the University of Calgary, Christophe Boesch from the Max Planck Institute of Evolutionary Anthropology, and their colleagues. They are a magnificent archaeological find – the first ever evidence of prehistoric ape behaviour anywhere in the world. Humans have a rich prehistoric past, informed by similar finds like the Olduwan sites. These unearthed treasures shows us how our ancestors developed the tools that continue to serve us well today. For chimps, this is the first time that such sites have been found.

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Bird-brained jays can plan for the future

By Ed Yong | October 16, 2008 10:00 am

Looking at Britain’s overcrowded prisons, Wembley stadium or the continual dithering over solid climate change policies, it would seem that many of us are really quite bad at planning for the future. Even so, most of us can still do it (even though some may do it very badly). This abilty isn’t there from birth; children only develop a sense of a future at the age of two and they can only plan for it from four or five. But eventually, everyone picks up the skill and up till recently, scientists believed that we were the only species that did.

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Many animals show behaviour that could be generously explained by future planning. Birds will often migrate to warmer climates, and bears will hibernate in advance of winter famines. But the world of modern biology resists casual anthropomorphism at all costs. Both animals and the scientists who study them) must work harder to prove themselves. Migrating birds or hibernating bears are not necessarily thinking ahead; they are most likely reacting to signals in the present that tell them the seasons are about to change. Their responses are instinctive.

To show true planning, an animal must do more than follow pre-programmed drives; they must anticipate their future desires and show new planned behaviours in response. Caroline Raby and colleagues from the University of Cambridge showed that a simple bird-brain – the beautiful Western scrub jay (Aphelocoma californica) – does just that. Jays store food in hiding places or ‘caches’ for times when food is scarce, and Raby’s studies suggest that this is more than an instinct that says: “Bury food when cold.”

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Chimpanzees make spears to hunt bushbabies

By Ed Yong | October 15, 2008 10:00 am

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Blogging on Peer-Reviewed ResearchIt is midday in Senegal and a chimpanzee is on the hunt. Its target is a bushbaby, a small, cute and nocturnal primate that spends its days sheltered in the hollow of a tree, beyond the reach of predators like the chimp. But this hunter is not like others – it is intelligent, it is dextrous, and it has a plan. Snapping off a thin branch, the chimp strips it of twigs, leaves and bark. And with its teeth, it sharpens the tip into a murderous point.

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It forcefully jabs its newly fashioned spear into the bushbaby’s hiding place, stabbing the hapless animal multiple times. The chimp breaks into the tree hollow that sheltered its prey and drags it from its hiding place, wounded and ready to be eaten.

Many animals, from insects to birds, are known to use tools, but chimpanzees are the most advanced non-human toolmakers of all. They crack nuts with hammers and anvils, and fish for termites using sticks. But fashioning weapons, and using them to hunt is a fresh and advanced trick, even for them, and a trait that was previously deemed to be uniquely human.

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9/11 memories reveal how flashbulb memories are made in the brain

By Ed Yong | October 14, 2008 10:00 am

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Blogging on Peer-Reviewed ResearchI have only ever seen one car crash and I remember it with crystal clarity. I was driving home along a motorway and a car heading the opposite way simply veered into the central reservation. Its hood crumpled like so much paper, its back end lifted clear off the tarmac and it spun 180 degrees before crashing back down in a cloud of dust. All of this happened within the space of a second, so the details may be different to what I remember. But the emotions I felt at the time are still vivid – the shock of the sight, the fear for the passengers, the confusion over what had happened.

Many studies have shown that peoples’ memories become particularly clear when it comes to traumatic or shocking events. Even learning about a shocking event, rather than witnessing it first-hand, can produce unusually clear recollections. Many of us still remember where we where when we learned that famous figures like Princess Diana or John F. Kennedy had died (I found out about Diana on the toilet).

Scientists have suggested that this type of event triggers a process that produces a very specific and exceptionally vivid type of memory called a ‘flashbulb memory‘. This concept has been kicking around since the 1970s, but the evidence that flashbulb memories actually exist is inconsistent.

Tali Sharot and colleagues from New York University decided to find some proper answers by studying the brain activity of people remembering a traumatic event. Doing such experiments would normally be ethically impossible – you cannot after all willingly traumatise someone in the name of science. But Sharot did not need to – unfortunately for us, the twenty-first century has already provided its fair share of traumas.

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The snake that eats toads to steal their poison

By Ed Yong | October 13, 2008 10:00 am

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Blogging on Peer-Reviewed ResearchMany animals use poisonous secretions to protect themselves from predators. But poisons are complex chemicals and can take a lot of energy to make. Why invest in them, when you can steal someone else’s?

20070130_snake.jpgPoison thieves are well-known in the animal kingdom. Many species of brightly coloured poison arrow frogs acquire their poisons from beetles, while some sea slugs make a living by hunting for jellyfish, transporting their stinging cells into their own limbs. Now, another species joins this guild of thieves – the tiger keelback snake, Rhabdophis tigrinis (image right, by Deborah Hutchinson).

The tiger keelback lives in Japan and uses its poisons for defence rather than attack. When threatened, it angles two glands on the back of its neck towards the predator. The fluid that oozes from these ‘nuchal glands’ contains chemicals called bufadienolides, that irritate airways and affect heart muscle. But the glands themselves lack any of the secretory cells that you might expect in a poison-producing organ. So where does the snake get its poison from?

The answer lies in its diet – the snakes eat poisonous toads (from which bufadienolides get their name), and defend themselves with the weapons of their prey.

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The brain's addiction centre

By Ed Yong | October 12, 2008 10:00 am

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Blogging on Peer-Reviewed ResearchIt’s mid-October. For most of us, our New Year’s resolutions have long been forgotten and our bad habits remain frustratingly habitual. The things that are bad for us often feel strongly compelling, be they high-fat foods, gambling or alcohol. And nowhere is the problem of addiction more widespread, serious and dangerous than the case of cigarette smoking.

800px-papierosa_1_ubt_0069.jpgSmoking is the leading preventable cause of death in the developed world, and in the UK, it kills five times more people than all non-medical causes combined. The dangers of smokers are both well-established and well-known, and surveys repeatedly show that the majority of smokers want to quit. But weaning oneself off a substance as addictive as nicotine is not easy.

People often view quitting smoking as a question of willpower – a problem of the mental world. But like all mental processes, addiction eventually boils down to physical matter, to our brains and the chemicals that reside within. Neurological studies have found that smoking causes long-term changes to various parts of the brain including the dopamine system involved in feelings of pleasure, and the amygdala, involved in emotional responses. Even cues associated with smoking such as the smell of smoke or the sight of a cigarette, can trigger distinctive patterns of activity in these areas, and are likely to contribute to the urges that smokers feel.

Now, Nasir Naqvi and colleagues from the University of Iowa have tracked down the neurons that control the addictive urges of smokers to a part of the brain called the insula. Located deep inside the brain, the insula is involved in emotion. It collects and processes sensory information from the rest of the body, and translates them into conscious emotional experiences, such as cravings, hunger or pain. And in doing this, the insula could control cravings for cigarettes in response to smoking-related cues.

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The heavy cost of having children

By Ed Yong | October 11, 2008 10:00 am

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Blogging on Peer-Reviewed ResearchWhile philosophers and poets muse on the meaning of life, natural selection casts a dispassionate eye on the whole affair. From the viewpoint of evolution, there is only one thing that matters – that we survive long enough to pass our genes on to the next generation, as many times as possible. And from the viewpoint of evolution, we are not doing a very good job.

415px-expecting_mother.jpgBirth rates in several countries around the world – the UK, Japan, China – are falling dramatically. Women are having fewer children and they are having them later, close to the end of their fertile period. But the fact that women undergo menopause at all seems strange, and the reasons for this reproductive expiry date has long puzzled biologists. There doesn’t seem to be any obvious benefit to ending a woman’s child-bearing potential with many years or decades to spare. Nor is menopause a symptom of our healthy modern lives – even in traditional societies, women often survived long past this point.

The favoured idea is that women retire early from child-bearing for the same reasons that athletes retire from their sports at a young age – their bodies cannot handle the strain. Childbirth is a taxing process for a woman and at some point, it becomes too risky for mother and child. Scientists have suggested that menopause is an evolutionary respite from the burdens of having children. Now, Dustin Penn at the Austrian Academy of Science and Ken Smith from the University of Utah have found compelling evidence to support this idea.

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