Question: is there any way to reverse evolve to solve an old problem

Sam Tazzyman answered on 17 Jun 2011:

Yes, sort of. There are several examples of this sort of thing. The first is in things like parasites and their hosts. There is constant evolutionary pressure to make a species evolve to be able to stop its parasites. But there is also constant evolutionary pressure to make a parasitic species be able to beat the defences of its host species. So they’re both evolving as fast as they can to beat the other species’ last new trick. Sometimes this can make things go in a circle, meaning they have to reevolve a way to beat an old trick that has again become new.

Another way is something called “convergent evolution”. This is when species evolve the same trick to beat the same problem, even though the species are only very distantly related. A good example is the fin on the back of sharks and dolphins – it looks quite similar. This is despite the fact that sharks evolved something like 420 million years ago and are fish, while dolphins evolved something like 50 million years ago, the ancestors of mammals who had been on the land. The mammals that are ancestors of dolphins were themselves descended from sea creatures back when mammals first evolved. So in a way dolphins re-evolved the dorsal fin to solve an ancient problem (how to keep upright when swimming).