(urth) Mystery of Ascia

[Lee Berman]

>Gerry Quinn: I concede that my use of the term Dollo's Law to cover general principles of 
>evolutionary irreversibility was incorrect.
 
I think it makes intuitive sense. Mixing up gene combinations is essential for survival of
a gene line allowing organismal adaptability. Sexual creatures do it, but even most asexual
organisms, including bacteria, have various means of swapping genetic material with each other.
 
Irreversibility is a huge evolutionary red flag. It will most often lead to extinction. If a 
gene line finds itself on an irreversible path of change it is a huge risk (since the original 
form was obviously a successful one in a given environment- changed environments usually change
back). So irreversibility is a rare exception while reversibility is the rule.
 
>It was never about skin colour.  [Nor is skin colour especially susceptible 
>to biased thinking, in my opinion.  The notion that those who believe in 
>racial differences are hypnotised by an obsession with skin colour is a 
>popular straw man which has little basis in truth.]
 
 
Perhaps I've been dense about the undertones of this discussion but I'm not really sure what you
mean by "those who believe in racial differences" and the lack of importance of skin color. What
IS important to those who believe in racial differences?
 
 
>So, my hypothethical Swedish tribe migrating to Africa would develop a unique 
>appearance; they would adapt to increased solar radiation, but not in 
>exactly the same way as other groups living in the same place have adapted. 
>By the same token, a tribe of Yoruba migrating to Sweden would, after 
>adaptation, still look noticeably different from the current Swedish 
>population.
 
What I think you continue to miss is that there is no "exactly the same way" groups of humans
adapt. There was no "original color" of Africans. There was always and will always be a range.
The color range of Africans today is not the color range of Africans 50,000 years ago. And it
will be a different range, 50,000 years hence.
 
If you took a sample tribe of Swedes and isolated them *in Sweden* or did the same for a group
of Yoruba *in Africa* and gave them 1 million years of (hypothetical of course) complete isolation
both groups would differ significantly from their non-isolated neighbors of the both past and that 
future. 
 
Your hypothesis is staged under unnatural conditions. Under natural conditions, admixture is an 
essential part of the composition of a gene pool. Even for bacteria.  It reduces irreversibility, 
which is necessary as explained above.
 
A gene pool is a dyanmic thing, in constant motion and change. It sounds like you are arguing that
a bear walking around the woods can never be in exactly the same spot, to the nanometer, with
the exactly same set of atoms composing its body. And the answer to that would seem to be, "so what?"
Are you arguing the bear isn't the same bear because it walked a few meters over and took a dump?
 
>That doesn't mean that Swedes don't have genes in their population - whether omnipresent but suppressed 
>by regulatory genes or simply at low frequency - for dark skin, flat noses, curly hair, and any other 
>traits that may be adaptive in tropical conditions.  It means that even if Swedish versions of such genes 
>are enhanced in the population, they won't be exactly the same versions in the same proportions that are 
>enhanced in other populations.
 
Are noses, hair shape and other tropical adaptive traits, the ones which are more important than skin
color to those who believe in racial differences?
 
There isn't such a thing as a "Swedish version" of a gene. While gene pools are mercurial, genes are not.
Changing one single base code among tens of millions on the gene for insulin is what makes people diabetic. 
Genes are copied faithfully person to person. Mutations are almost always harmful.
 
A given gene expresses itself differently based on the other genes on a chromosome it happens to share, on 
the combinations of genes on other chromosomes of the organism, on the development and environment and
diet of the organism, etc. 
 
Think of the skin color of each human being as a result of throwing 100 dice simultaneously. The dice
remain the same. It is the vast array of possible combinations which provide different results. The exact
combination really doesn't matter. Does it matter whether a certain skin shade of, let's call it 450, is the 
result of 100 sixes in one individual and 50 sixes in another? No, the outward expression of color 450
is all that matters. 
 
And the presence of ones, two, threes etc. on the dice remain the same, generation after generation no matter 
how they are mixed in a particular generation. Selection may shut off a particular numeral for a while, but it is 
still there on the die, hidden from view, ready to turn on again one day.
 
>However, I still think a form of evolutionary irreversibility will apply such that there can never be a "natural 
country type".
 
I don't understand what you are arguing. If evolution were irreversible wouldn't that argue FOR a "natuaral
country type"?