On 9/24/05, Richard Baker <[EMAIL PROTECTED]> wrote: > > Leonard said: > > > How can blind cave fish could result purely from random mutations > > (among several sub species no less)? I believe that several billion > > tetras must have been sucked into Mexican caves in order for > > "random mutations" to account for this. > > You do know that there's more to Darwinism than random mutation, > right? The important part is natural selection, which is just a > shorthand for organisms with slightly different genomes having > slightly different average successes at reproduction. Over many > generations, even slight differences in average reproductive success > can have large effects on populations. > > I would imagine it would take relatively few generations for cave > fish to become blind and then eyeless, as eyes are quite complex > structures that require a large investment of resources to build > correctly. As most random mutations in the genes controlling eyes > would tend to produce less effective eyes, the randomness of mutation > and the selection pressure would both strongly tend towards eyeless > forms.
I saw mention in a recent article of Discover magazine, perhaps the latest issue, that ivory poaching is Asia is driving elephants towards tusklessness. The article did not specify, but I would guess the mechanism is that elephants with larger tusks are getting killed for the ivory and therefore aren't breeding as much. So the elephants that breed are the ones with smaller tusks. Average tusk size therefore continues to decrease. This is another case where it is not a random mutation driving the change, rather it is an external evolutionary pressure dictating which animals get to breed and which die before breeding. Mauro _______________________________________________ http://www.mccmedia.com/mailman/listinfo/brin-l
