Todd:
>(3)  The way in which the variation in genotype and its
>consequent variation in phenotype arises in the first place is
>through random mutation.
>
>The thing that I have found most disconcerting is that there is
>virtually no empirical evidence for (3).

Do you mean that there is no evidence for mutations, or is it the random
part that is unsupported?

It may be that what are considered mutations are really the activation of
previously "dormant" genes. Many researchers believe that most of our DNA
is simply along for the ride, containing a high percentage of genes that
appear to have no utility. Perhaps selective pressures are acting on less
of an actual mutation, than a "mining of the baggage" already contained in
the DNA.

Neotony is one example. The ability for, say, lactose digestion simply
remains--the genetic basis for it is not "switched off". Our ability to
secrete salive with amalase is probably another example. Even the so-called
neolithic blood types are not brand new mutations but part of primate
evolution as well. Perhaps the selective pressures of agriculture turned on
the genes responsible for that blood type.

In other words, natural selection may be acting upon, not only random
mutations (which almost _have_ to happen, don't they?) but on already
existing code.

Further, viruses may play a role in turning on (or off) certain genes, as
well as transmitting new genetic material across a population (which is why
the evolved to be contagious and host cells have viral receptors?). Such
transmission would be lightning fast compared to the selection of random
mutations.

Cheers,
Kirt

Secola  /\  Nieft
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