January 2009 - Biology Issues

Biology Issues

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Biology Issues - January 2009

Darwin and the web of life

January 30th 2009 10:23

This article in New Scientist by Graham Lawton, titled "Why Darwin was wrong about the tree of life", has sparked a minor uproar - or rather, this was achieved by the front cover of the issue in which it appeared. Readers have felt that the cover title is misleading and may provide grist for the creationist mill. In large letters, it reads "Darwin was wrong", though with a subtitle "Cutting down the tree of life". The article itself, which should give no comfort to creationists, is fascinating and informative, though I personally think that it may itself engender some confusion. I don't think it quite measures up to the message conveyed in either title. Its focus is upon whether most of the life on Earth has evolved in a branching tree fashion or whether it's more like a web, with horizontal gene transfer (as opposed to vertical gene transfer to progeny) taking place on a large scale. This is an interesting and worthwhile question, and it is the centre of much current research and controversy. But back to why I think the article may be misleading (some have cited it as an example of journalistic hype, and personally I do feel it was somewhat irresponsible. But I won't push the matter further here):

(I have basically paraphrased a message I posted on richarddawkins.net

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What would ET look like?

January 29th 2009 03:09

In this interesting article by Michael Shermer, the odds of intelligent aliens looking like us are considered. Is it at all likely? Are Hollywood's depictions of intelligent extraterrestrials too anthropocentric? Shermer thinks that the odds of ET being bipedal and humanoid are very low indeed. Others think it not unreasonable to suppose that they may well be bidepal owing to convergent evolution. Still others think that it is all but inevitable. For my part, I think that we can't know with any real confidence because the issues are entangled and complex, and there's a great deal we don't know about the prospects for extraterrestrial life (let along intelligent extraterrestrial life) and much else besides (even about evolution on this planet), but if I had to make a guess, I'd say it's fairly likely, given some conditions being met.

An excerpt from the article

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What really killed the dinosaurs?

January 26th 2009 04:24

Recently, it has become apparent that the extinction of the dinosaurs was more complex than had previously been envisaged. We thought we had a pretty good handle on the cause of their demise: basically, a gigantic meteorite striking the Earth and releasing the energy of 10 billion Hiroshima bombs, resulting in the extinction of some 65 percent of all species, including the dinosaurs (except birds), pterosaurs and plesiosaurs (contrary to popular misconception, these latter two groups were not part of the Dinosauria, though they were related to them). But nagging questions have cropped up since this supposedly neat explanation was proposed. Why weren't the amphibians wiped out as well? The environmental changes that were thought to have been kicked off by the meteorite, including raging fires and acid rain, should have been at least as devastating to the amphibians as they were to the dinosaurs. After all, amphibians are highly sensitive to chemical perturbations in their habitat. Yet this group, despite suffering somewhat, made it through to the Cenozoic era (the current era), as did many other groups. Is it possible, then, that the meteorite wasn't so much the cause of the dinosaur's extinction as it was the last nail in the coffin for them? There is evidence suggesting that by the late Cretaceous, they were doing rather badly, perhaps owing to widespread climate change. What does seem fairly certain is that, right after the extraterrestrial impact, there was a so-called "fern spike" - a massive increase in the number of ferns, which are good at taking over when other plants have died off. With a lack of plants to eat, the herbivores would have starved, and the carnivores that fed on them would have gone on the same way. It is entirely conceivable that had the impact not occurred the dinosaurs would have eventually gone extinct anyway. But we'll probably never know for sure. Sometimes, groups that are doing badly manage to bounce back (due to fortuitous events that happen to come to their rescue, not destiny). Still, what is clear is that the story of the dinosaurs offers many lessons about natural history, and the more we look, the more complicated and indeed interesting this story becomes.

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The Fermi paradox

January 24th 2009 07:44

The Fermi paradox is the apparent contradiction between optimistic projections made from the famous Drake equation - which predicts that there should be hundreds of thousands of technological civilisations in our galaxy, even if only a small fraction of all planets within it are habitable, and only a small fraction of those have witnessed the evolution of intelligent life - and the lack of evidence for any such civilisations. Surely, if there are so many aliens out there, shouldn't we have detected their presence in some form or other by now? Some scientists have taken this cosmic silence as evidence that ET simply isn't there. Others have tried to resolve the paradox by devising some scheme in which these civilisations do exist, but where we're somehow overlooking them. In this fascinating lecture (titled "Why aren't the aliens everywhere?") by Seth Shostak, an astronomer who works with the SETI (Search for Extra-Terrestrial Intelligence) Institute, some of the possible answers to Fermi's conundrum are considered. To my mind, I think that the most plausible solutions - assuming that the galaxy is inhabited by beings with the capability of travelling interstellar distances - are those that try to find analogues of ecological processes limiting exponential growth, or that consider how some pieces of galactic real estate might be less valuable than others and that advanced civilisations tend to cluster around energy and resource rich areas and perhaps have little incentive to colonise elsewhere.

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The Extended Phenotype today

January 21st 2009 09:46

While The Selfish Gene was to a large extent an exposition of a view that had been pioneered (albeit implicitly) by other workers, this book is Dawkins’ unambiguously original contribution to the study of animal behaviour and evolution. Building on the aforementioned work where the gene-centric view of evolution was made explicit, this edition, apart from clearing up some common misunderstandings about the 1976 classic, invites us to view genes as the centres of interlocking webs of power radiating out from the bodies of organisms and into the world. This is why genes have extended phenotypes, because their consequences reach out across animate and inanimate entities, beyond the bounds of the organism-proper they ride around in; they manipulate or otherwise influence “vehicles” and objects in ways conducive to their own propagation. A beaver’s damn is no less a part of the phenotype of the genes predisposing beavers to damn building than the limbs and neural circuitry that facilitate such activity. Perhaps most fascinating, there are certain phenomena that are puzzling if one were trying to interpret them from the point of view of individual-level selection. An example of such is meiotic drive. If one adopts the extended phenotype/gene-centric view, the puzzle disappears. Of course, it could be argued that meiotic drive is an example of unambiguous gene selection, while macro-level phenomena like the evolution of limb morphology are best left to the orthodox account. But the beauty of the extended phenotype is that all these things are seamlessly incorporated and come to be seen as manifestations of the same underlying thing: genes using the levers of power at their disposal. Sometimes they propagate themselves by programming animal brains and using these as their proxies, other times through the subversion of the meiotic lottery or replication throughout the genome.

This book, despite its difficulty in parts, should be read by anyone interested in evolution, from teachers to lay people (though they should prepare themselves by first reading The Selfish Gene); it should definitely be required reading for ecologists, professional biologists, and ethologists. This is, simply, because the book is extremely bold and extremely fascinating. It’s so fascinating that one often has to put it down and pause to consider whether it might all actually be the result of a misunderstanding. But the arguments are carried through with the clarity and passion that Dawkins so eloquently combines in all his writing. It is his most technical book, and some parts of it require serious mental exertion to extract the full message contained therein, but the effort is well worth it

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Problems for evolutionary psychology (or rather, Pop Evolutionary Psychology)

January 20th 2009 04:22

Evolutionary psychology is the field of psychology that aims to uncover the evolutionary forces that shaped out minds. It has tended to focus upon what sorts of adaptive pressures our ancestors faced and how these pressures moulded the psychological predispositions we have. It is a controversial field, with some scientists enthusiastically embracing it, while others see it as being of relatively little value (and perhaps as representative of what they fear to be a mania towards seeing everything as a Darwinian adaptation, so in that respect it is harmful as well). This article by David J. Buller in Scientific American spells out four fallacies of "Pop Evolutionary Psychology" (Pop EP "holds that the human brain has many specialized mechanisms that evolved to solve the adaptive problems of our hunter-gatherer ancestors"). The author explains why he thinks that this variant of EP is deeply flawed and why EP must strive to become more careful in its analysis of human nature. Certainly it has given me pause, for I had (perhaps naively) presumed that the arguments of Pop EP were quite compelling.

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