Monday, June 18, 2007

Comet, maybe

I am finally getting around to reading Richard Dawkins' The Ancestor's Tale, his big account of the evolution of life on Earth. Much of what he writes about I already know, but Dawkins is fun (and illuminating!) to read no matter what his subject.

Early in his backwards pilgrimage to the origins of life he has a few words for those who romanticize pre-industrial and pre-agricultural societies:
It has lately become fashionable to regard hunter-gatherers and primitive agricultural societies as more "in balance" with nature than us. This is probably a mistake. They may well have had greater knowledge of the wild, simply because they lived and survived in it. But, like us, they seemed to have used their knowledge to exploit (and often overexploit) the environment to the best of their abilities at the time...Far from being in balance with nature, pre-agricultural hunter-gatherers were probably responsible for widespread extinctions of many large animals around the globe. Just prior to the Agricultural Revolution, the colonization of remote areas by hunter-gatherer peoples is suspiciously often followed in the archeological record by the wiping out of many large (and presumably palatable) birds and mammals.
First, note in this short paragraph the words "probably," "may," "seemed," "probably," and "presumably." Dawkins is often lashed by the antievolutionists as a "dogmatic" scientist. But like any good scientist, he is generous in his expositions with qualifiers, when qualifiers are called for.

Were humans responsible for the large bird and animal extinctions at the end of the last Ice Age? There is also the matter of climate change as the northern continents emerged from under the ice. The debate has been vigorous and the jury is still out. You may have read recently about new evidence for the explosion of a massive comet over southern Canada about 13,000 years ago. The energy released by such an event would have sent a shock wave across the continent that would have knocked woolly mammoths off their feet and ignited fires in anything that could burn: One more candidate for cause of the Late Pleistocene megafauna extinctions. Maybe our human ancestors were not as deeply implicated in the demise of the big beasts as Dawkins suggests.

Maybe. Possibly. Presumably. Patience!! It's a lovely detective story. The geologists, paleontologists and archeologists will continue gathering evidence. At some point the weight of evidence will be sufficient to convict -- or let the accused walk free. As always in science, it will be evidence, not dogma, that will decide.