In "Re: Don't forget about me! (distal vs. proximate)",
[Berlinski and Dover quotes removed...]
> I take these modular genes and Pax-6 fall in the design category
> and indicate that design precedes application and is used in many
> different applications. I don't see straightforward natural selection
> in it, although natural processes are undoubtedly involved.
I discussed this previously in:
I conclude that there is no a priori reason provided to suppose
that design events must have stopped or, at least, that we shouldn't
consider the possibility that a designer could remain active.
But back to the unrelated question about the evolution of eye
regulatory genes: To be more specific, what part/s of Pax-6 do you
think fall/s into the design category? The linear sequence? Its role
in eye development? Its role in other developmental pathways?
Pax-6 clearly appears as a variant of a class of transcriptional
factors that predate the emergence of eyes. We know from experiments
that transcriptional factors can get recruited into new roles in the
regulation of genes for which there was previously no interaction. So
the recruitment and/or diversification of the Pax-6 progenitor into a
regulator of eye-spot development doesn't seem too much of a stretch to
me. Certainly one would be hard pressed to claim that event required
the direct intervention of a designer. Here's a web page I found on the
evolution of the eye. It's not complete or terribly detailed, but at
least it summarizes a little of the detail (Discussed by Berlinski?
Are you kidding?):
And what part of modular genes fall into the design category? When
were the design events for these genes? Eukaryotes share many modular
regulatory sequences with eubacteria and archeabacteria, which
suggests that the design events must have preceded the split
between the three kingdoms roughly 1-2 billion years ago (e.g. The
two-component regulatory system initially discovered in bacteria is
found in all three kingdoms).
So what part of the evolutionary history is questionable? The origin
of a particular module or its subsequent recruitment for alternate
uses? If it's the origin of the modules which required design
events, perhaps the examples of eye evolution aren't terribly
helpful: the "modules" involved in eye development appear to have
been present long before eyes came about.
Again, I would strongly encourage anyone who is seriously interested
in questions about the role and evolution of Pax-6 in cell development
to look up the relevant, recent papers in Medline. Berlinski, for
all his knowledge of the history of math, is definitely an uninformed
hack when it comes to biology (as indicated by the quoted material).
Tim Ikeda (email@example.com)
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