In article <email@example.com>, James Foster <firstname.lastname@example.org> wrote:
>L.A. Moran (email@example.com) wrote:
>: I'm a little confused here. Do you mean to say that natural selection >: explains the "development of life" and that natural selection explains "what >: we observe in nature"? > >: Your statements might be considerd to be accurate if you were referring to >: "evolution" but not if you mean "natural selection". Please clarify.
>Natural selection refers to the tendency of the environment to favor the >ability of organisms with one trait to survive over those with another >trait. (Question to biologists: is that fair?) > >Evolution is the tendency of a distribution of traits to drift over time. >That is, evolution is change in organisms across generations. Natural >selection is the mechanism which drives this drift. > >We have observed both natural selection AND evolution: in the lab AND in >nature. Selection explains the distribution of traits and the patterns >of survival that we see at any given time. Selection in the past, coupled >with evolution, explain the distribution of traits we see now. >Together, they explain the "tree of life" and the remarkable diversity >and adaptiveness we observe in nature. > >Is that what you were asking?
More or less. I was trying to find out whether you attributed all of evolution to natural selection. Apparently you do. I don't.
I believe that the current tree of life is largely the product of contingent events (including genetic drift). This is not to deny that adaptation occurs since there are many clear examples. I simply want to point out that many of the historical events of the past may not be due to selection. I also believe that most of evolution at the molecular level can be attributed to the fixation of neutral alleles by drift. This has nothing to do with natural selection and it accounts for much of the deversity that we see in modern populations.