(urth) Mystery of Ascia

[Gerry Quinn]

From: "Lee Berman" <severiansola at hotmail.com>

>>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.

That may to individual genes or structures over short timescales (with large 
changes over long timescales Dollo's Law does apply and irreversibility is 
the rule, not the exception).  It cannot reasonably be explected to apply to 
particular patterns or constellations of traits, because the number of 
possible patterns is enormous, and few environments impose selective 
pressures so strong as to preclude all but one possibility.



>>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?

I was merely responding to your assertion that "among visible human 
features, surely none is more subject to biased thinking than skin color". 
Race is (almost) invariably identified by multiple traits, of which skin 
colour is just one.  [I seem to recall some so-called research in which skin 
colour was used as the sole proxy for race, but I suspect these studies were 
for the most part bogus science intended for propaganda purposes.]


>>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.

How can I be "continuing to miss" exactly what I am saying???


> 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.

Well, that is certainly so.  But do you doubt that if you took a tribe of 
Swedes and a tribe of Yoruba, and isolated each under isolated conditions, 
they would, even after adapting well to the local environment, look 
different?  [Indeed, I think if you took two tribes of each, you would end 
up with four distinguishable peoples.]

That is an example of irreversibility, although it is not an example of 
Dollo's Law.  I think such irreversibility is the rule, not the exception.


> 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.

Most scientific experiments are conducted under unnatural conditions, and 
most thought experiments even more so.  It does not render them invalid. 
Here we are conducting a thought experiment with regard to the determination 
of a "natural country type".  The theory of "natural country types" would 
predict that the two or four tribes in our gedanken would come to look 
alike.

Also, you have an exaggerated idea of the extent to which occasional gene 
transfer acts to induce homogeneity in a population, whether natural or 
experimental.  The failure to detect Neanderthal genes among Yoruba and San 
is an example of how substantial inhomogeneity can persist and grow within a 
single species.


>>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?

Along with skin colour, they are among the most commonly known signifiers of 
race, certainly.  (Specialists such as forensic anthropologists will 
recognise many more.)



> 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.

Not true.  Here, for example, is Wikipedia on the subject of alleles:
"It is now appreciated that most or all gene loci are highly polymorphic, 
with multiple alleles, whose frequencies vary from population to population, 
and that a great deal of genetic variation is hidden in the form of alleles 
that do not produce obvious phenotypic differences."

We may safely asssume that certain alleles are common in Sweden and rare in 
Africa, and vice versa.


>>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"?

No, quite the opposite!  Consider a population that is adapted to country A, 
then moves to country B and adapts to it.  Now assume they move back to 
country A, in which conditions have not changed.  If there is a natural 
country type, they should revert to their original form.  If evolution is 
irreversible, that cannot happen.

- Gerry Quinn