Monday, June 02, 2008

The Ancestor's Tale - Richard Dawkins

Richard Dawkins has mostly now become famous as a champion of atheism, but of course his original and main job is as a biologist and specialist on evolution. This marvellous book gives an interesting new perspective on the usual evolutionary tale - instead of the traditional method, starting with bacteria and climbing the ladder via fish and dinosaurs to us fantastic mammals, it does the whole journey in reverse. Dawkins has taken his concept from the Canterbury Tales, where various pilgrims (species, orders, phyla, kingdoms) are heading to a single destination (Canterbury/the origin point of all heredity), meeting each other at various points en route and exchanging tales as they go. Starting off with homo sapiens, we head back through the immediate human ancestors, then get our first rendezvous with the apes, then the monkeys, and so on, right back to the 39th rendezvous in the furthest depths of prehistory.

As well as providing information about the species themselves (including some good bits of pub trivia), the various tales are also used to illustrate particular facets of evolutionary theory. To pick a few examples, The Howler Monkey's Tale shows us the different ways that colour vision has evolved in primates; The Seal's Tale explores the evolutionary pressures that cause sexual dimorphism and different mating patterns; The Redwood's Tale looks at different dating systems, from tree-ring counting through core sampling to carbon dating; and The Marsupial Mole's Tale looks at parallel evolution in geographically separated populations, where the marsupials of Australia evolved to fill the same ecological niches as their placental cousins elsewhere, and often ended up looking extremely similar. Obviously, they're not "tales" as such, but short essays, and together they combine to produce one of the most comprehensive accounts of evolution that I've read.

If you should be so incautiously affectionate as to stroke a shark, you would find that its whole skin feels like sandpaper, at least if you stroke it "against the grain". It is covered with dermal denticles - sharp, tooth-like scales. Not only are they tooth-like, but the formidable teeth of a shark are themselves evolutionary modifications of dermal denticles.
Sharks and rays almost all live in the sea, although a few genera venture up estuaries and rivers. Freshwater shark attacks on humans used to be common in Fiji, but that was when humans were cannibals. All but the choicest cuts were discarded into rivers, and it would seem that sharks were attracted upstream by the smell of leftovers from cannibal feasts.

Dawkins writes in his familiar style, with occasional flashes of acerbic wit and barbs aimed at idiot creationists, and only the odd moment of annoying self-congratulation. Some of the technical bits are hard going in places, but he does a good job of making the trickier statistical points as clear as possible without dumbing down. I've been reliably informed that his computer-based analogies are a little iffy, but in general this is an accessible, entertaining and informative account that really gets into the meatier details of how evolution works, and how it all happened. Because of the structure, Dawkins only really has room to cover the creatures (and other organisms) whose evolutionary line directly connects with our own, so dinosaurs don't get much of a mention, but he still elegantly sends them off with the eerily appropriate Ozymandias; otherwise, it's ancestors all the way, with a handy graph at each chapter to show how long ago they diverged. One minor quibble I'd have is the number of times Dawkins refers to his other books, though I can quite understand his desire not to repeat himself when covering much the same ground - and in fact it's not that much of a quibble at all, because now I'm quite inspired to go out and read more of them. Very good stuff.



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