August 19th, 2007


Evolution: Puzzled by the Puzzlement

So the big science news I've been stumbling across repeatedly for the past week is the new evidence that indicates that homo habilus and homo erectus co-existed for half a million years. Gasp, shock, says the news: does this mean that erectus didn't evolve from habilus?


Okay, am I missing something, or are these science writers *seriously* missing the point here? Unless you take the most ridiculously extreme view of evolution, an X-Men-ish view that a new species will not only inevitably but quickly supplant the old one, it's entirely reasonable that a successor species will co-exist with its progenitors for quite some time. Indeed, it would seem to me to be a perfectly normal state of affairs unless at least one of the following pertains:
  • there is an environmental shift that greatly benefits one species over the other;

  • the two species are inherently in deep competition with one another;

  • the resources available to both species aren't sufficient to support both.
Sure, these factors do tend to come into play eventually, but why is everyone so sure that it's immediate? It doesn't seem any more obvious to me that there must be only one species of genus homo at a time than that there would be only one species of bird at a time.

If the species aren't in direct competition for scarce resources, the effects of evolution are going to be strictly statistical, and I don't see any reason why that would be quick. The better-adapted species will *eventually* outproduce the less-adapted one, sure. But if there's enough space and resources for both, it just doesn't strike me as surprising that that could take a very long time. Am I missing something here?