送交者: xh 于 2005-3-17, 12:28:25:
回答: 对达尔文进化论的疑问 II 由 AI 于 2005-3-17, 11:26:39:
Certain mechanism that causes mutations might have a tendency towards particular basepair changes. At the molecular level, it might fit into 'the least potential energy principle' at a given condition.
However, certain changes on DNA does not impose a directional change towards fitness. So the changes on fitness by mutations can be viewed as 'random'. 1) information flow DNA->protein->fitness, not reverse. 2) even the same mutation in an animal might affect fitness differently given a different environment.
As to the unbalanced leg hypothesis rised before, I was told that in dogs, a condition called hip dysplasia affects left hip more than right hip. It turns out that two different groups of genes independently control hip bone alignment on opposite sides of the body. Quite interesting.
One of my Genetics teacher told me that 'evolution is a poor kid with a broken car, he has to use whatever to make it go, chicken wire if it works'.