At 05:16 AM 7/24/00 -0500, Paul Nelson wrote:
>Doug Hayworth wrote:
>
> > If one does NOT accept common ancestry
> > (or, speaking in terms of forward time,
> > speciation), then there is nothing left
> > worth discussing with him/her relating
> > to evolution. Such a person has turned
> > him/herself off to the validity of my
> > entire scientific discipline at such a
> > fundamental level that we are without
> > any common ground.
>
>I take it that by "common ancestry," Doug means the
>theory of the monophyly (or shared common ancestry)
>of life on Earth, where any extinct or extant organism
>shares at least one organismal ancestor in common
>with any other organism, namely, the Last Common
>Ancestor, often abbreviated LCA or LUCA.
>
>If so, then one can certainly reject or doubt this theory
>and remain fully within the discipline of evolutionary
>biology.
Just for the record, I was careful to leave some room for degrees of common
ancestry acceptance. I said, "I have to conclude that the person who does
not accept common ancestry and speciation at levels much deeper than
"varieties" or "races" of a species (i.e., much deeper than
microevolution), simply has not examined the compelling manifold
evidence." I thought that I was quite clear on that point. Although I
find the evidence compelling for common ancestry down to the deepest
levels, I was not requiring that view on Bob's part (or anyone else's) in
this post.
I don't think the Doolittle stuff undermines the general reality of common
ancestry, namely that descent with modification and the multiplication of
species has characterized the history of life on earth. Yes, alternative
modes of transmission that result in introgressive, reticulate, and
horizontal "descent" and therefore cause a decoupling of different gene and
organismal lineages, etc. do pose a problem for producing a single
phylogenetic tree of life. This is old news. But this does not undo the
reality of common ancestry in the broad sense. Doolittle could not even
talk about his ideas without assuming a predominance of "normal" common
ancestry in the history of life.
Doug
P.S. What is your intellectual (or rather apologetic) goal in holding out
against common ancestry, especially for that of humans with primates and
other mammals (which is very recent)?
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