Re: [asa] How big a deal is homology?

From: Rich Blinne <>
Date: Wed Mar 28 2007 - 15:15:04 EDT

On 3/28/07, Terry M. Gray <> wrote:
> However, the breaks that make for morphological taxonomy aren't
> really there for molecular taxonomies. But the taxonomies match up
> for the most part. This, I think, is the remarkable INDEPENDENT
> evidence for evolution (and the fact that there is a huge temporal
> gap between the two data sets).

An interesting paper will be in tomorrow's Nature that confirms the
molecular biologists with respect to timing of the rise of mammals and the
end-Cretaceous mass extinction. The morphological folk said it happened
after and the molecular folk before. That latter appear to be correct.

> The new study confirmed and elaborated on earlier research by molecular
> biologists indicating that many of today's mammalian orders originated from
> 100 million to 85 million years ago. The reasons for this evolutionary burst
> are not clear.
> Drawing on both molecular and fossil data, the researchers said they found
> that the "pivotal macroevolutionary events for those lineages with extant
> mammalian descendants" occurred well before the mass extinction and long
> after. They emphasized that the molecular and fossil evidence provide
> "different parts of this picture, attesting to the value of using both
> approaches together."
> But the researchers conceded that much more research would be required to
> explain "the delayed rise of present-day mammals."
> Ross D. E. MacPhee, a curator of vertebrate zoology at the *American
> Museum of Natural History*<>who was a team member, said that paleontologists were previously dubious of
> the claims by molecular biologists of such an early ancestry of today's
> mammals. The fossil record of mammals in the Cretaceous period, they
> contended, was too sparse to support such an interpretation.
> "Now we know the ancestors of living mammal groups were there, but in very
> low numbers," Dr. MacPhee said.
> "The big question now is what took the ancestors of modern mammals so long
> to diversify," he continued. "Evidently we know very little about the
> macroecological mechanisms that play out after mass extinctions."

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Received on Wed Mar 28 15:15:50 2007

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