Re: Evolution: A few questions

On Wed, 23 Jun 2004 17:50:31 -0400 bivalve
<bivalve@mail.davidson.alumlink.com> writes:
> As Dave already indicated, the tadpole comparision is to indicate
> that if millions of tadpoles make the transition from fish-like to
> tetrapod lifestyles every year, it does not seem like an
> insurmountable morphological barrier for evolution. Amphibian
> larvae are not taphonomically durable. Their fossil record is poor,
> so it's hard to tell to what extent a larval developmental stage was
> present in the earliest amphibians. I'd guess that the salamanders
> are probably closer to the ancestral form in that regard, with a
> less dramtic change than in frogs and toads.
>
<snip>
Given the lack of fossil amphibian larvae for the reason cited, there is
a problem deciphering the ancestral stages. I am guessing that it should
be possible to decipher the developmental history from the genome and
proteome, especially working out when the various /hox/ sequences
activate and what distinctive results they trigger. However, the
sequencing of enough species to solve the problems seems unlikely in the
near future. I don't recall any amphibians on the list for sequencing,
nor reptiles. We have fish and mammal sequences for comparison, and to
help us understand gene function. But it does not look as though the main
gap between fish and mammals will soon be filled. In contrast, shells
make such lovely fossils.
Dave
Received on Wed Jun 23 20:07:49 2004