Joined: Sep. 2002
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|Done, but he has been asked before. |
Thanks. That's what we thought, but he repeated the claim, so we were wondering.
Just to make sure jerry didn't miss the question the first two times:
Any luck on getting that citation for the Grants claiming it takes 23 million years for one species to appear?
Well, he finally answered, sorta.
|jerry: By the way, it was 32 million years not 23 million years. I had a dyslexic moment as I remembered incorrectly but a friend corrected me. The Grants referred to the works of some researchers who were named Prager and Wilson. So maybe you should write the Grants and ask for the cite. It was in a presentation they made at Stanford. |
His answer is "Look it up yourself."
I looked up Prager and Wilson's paper. They are tallking about the development of complete hybrid inviability. P&W found that certain groups of organisms, birds and amphibians in particular, lose hybrid viability very slowly. 20-30 million years (which suprised me). However, other groups, such as mammals lose it much more quickly (by around a factor of ten): 2 - 3 million years
Prager & Wilson, Slow Evolutionary Loss of the Potential for Interspecific Hybridization in Birds: A Manifestation of Slow Regulatory Evolution, PNAS 1975.
Excellent read. Now consider jerry's actual statement.
|jerry: The Grants who investigated the finches of the Galapagos said it would take 23 million years for a new bird species to arise. |
It wasn't the Grants, it was 22 million years, and it didn't refer to new species. That is unless you consider the turkey and the chicken, or the duck and the goose to be the same species. Because those are the sorts of hybridizations that are at issue in the study. As usual, they are confused by the fact that reproductive isolation is a continuum and that this supports the evolutionary hypothesis.
Indeed, the title refers to *interspecific* hybridization, meaning hybridization *between* different species.
Here's something else in the paper that's of some interest for a paper written a quarter century ago.
|The above observations are consistent with the hypothesis that evolutionary changes in regulatory systems, that is, changes in the patterns of gene expression, provide the basis for both anatomical evolution and the evolutionary loss of hybridization potential.|
Several authors have suggested that in order to understand organismal evolution one needs to focus attention on the control of gene expression rather than on the amino acid sequences of proteins coded for by structural genes
They also point out that avians may be the victims of an "inflated system of organismal classification". (We tend to think of species that can hybridize as being in the same genera.)
Actually, whether or not these populations are actual species yet in the strict sense of the term is irrelevant. The fact remains they are morphologically and ecologically distinct, and reproductively isolated, which can only lead to further divergence. In other words, they are species in all but complete post-zygotic isolation.
Those who know the truth are not equal to those who love it-- Confucius