Re: Human Evolution is Categorically Distinct

From: Tim Tyler (tim_at_tt1lock.org)
Date: 12/29/04 

Date: Wed, 29 Dec 2004 17:13:11 +0000 (UTC)

EKurtz99 <EKurtz99@twilightzone.com> wrote or quoted:
> "Jim McGinn" <jimmcginn@yahoo.com> wrote [or quoted]:

> > "Humans evolved their cognitive abilities not due to a few accidental
> > mutations, but rather, from an enormous number of mutations acquired
> > though exceptionally intense selection favoring more complex cognitive
> > abilities," said lead scientist Bruce Lahn, an assistant professor of
> > human genetics at the University of Chicago and an investigator at the
> > Howard Hughes Medical Institute.
>
> Who believes otherwise?

Conventional wisdom is that the unusual features of human brain are the
product of a rather small number of genetic changes - corresponding to
the fact that we share an overwhelming proportion of our genes with
our nearest relative species.

> >From a genetic point of view, some scientists thought that human
> > evolution might be a recapitulation of the typical molecular
> > evolutionary process, he said. For example, the evolution of the larger
> > brain might be due to the same processes that led to the evolution of a
> > larger antler or a longer tusk.
>
> Who believes such nonsense?

[...]

> > "The making of the large human brain is not just the neurological
> > equivalent of making a large antler.
>
> Again - who believes that big brains are the human equivalent of big
> antlers?

Big brains and big antlers have one /very/ significant thing in
common - they are both the result of "runaway" sexual selection.

>>From that point of view, the large human brain is exactly the
neurological equivalent of making a large antler. Even if a
few more genes are involved, the underlying process is
very similar.

> > Rather, it required a level of selection that's unprecedented,"
>
> ...unprecedented when you compare it to rats and mice.

Selection pressures on humans are likely to be feeble - compared to the
selection pressures on rats and mice.

Humans are rather K-selected - while rats and mice are rather r-selected,
allowing for more births, more deaths - and greater variance
in reproductive success in each generation.

Rodents combine this with a more rapid generation time. I should think
they evolve like the clappers compared to us. 

-- 
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