> >Irreversibility has long been recognized as a general characteristic of
> >evolution, micro and macro. Dollo's Law, isn't it?
> Admittedly I am not familiar with that, but my understanding of evolution,
> based on reading the books by Futuyma and others, suggests that
> this is not
Dollo's Law is a generalization of the idea that if a series of evolutionary
changes occur, it is very unlikely that the will reverse in the same order
later. Thus if we see what appears to be "reverse" evolution, we expect
there will be indications that the process wasn't actually "unwound." For
example, flippers in whales appear to resemble fins in sharks, but it is
simple to show that they are not anatomically "fins." This does not apply
to the case of the peppered moth, since only one gene is involved (except
form insularia), and the typica form has never been eliminated.