[Marxism] Humans have evolved from a common genetic pool

[Jeff Rubard]

> Message: 13
> Date: Sun, 1 Jul 2007 23:46:12 -0400
> From: Greg McDonald <sabocat59 at mac.com>
> Subject: Re: [Marxism] Humans have evolved from a common genetic pool
> To: marxism at lists.econ.utah.edu
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>                 `
> December 16, 2005  http://www.sciam.com/print_version.cfm?
> articleID=0002E7CA-F27B-13A1-AFAA83414B7FFE9F
>
>                 Researchers Identify Human Skin Color Gene
>
> Ten years ago researchers embarked on a study of zebrafish--a quick
> breeding aquarium pet. While searching for cancer causing genes they
> ended up isolating the gene that makes European skin white, thanks to
> the golden variant of the fish.


[...]

Uncovering this gene, however, does nothing to solve the question of
> why Europeans developed lighter skin in the first place--though it is
> believed to represent an effort to boost production of vitamin D in
> sun-deprived latitudes. Neither does the work reveal the genetic
> basis for the lighter skin tone of some Asians. The finding does
> promise, however, to yield new insights into potential skin cancer
> treatments and other skin-related diseases.


This is interesting stuff, but even I took the trouble to say that
skin color was genetically determined -- which doesn't by itself
give us a meaningful evolutionary story. To say that genetic makeup
must be seen as determined by natural selection on pain of irrationality
doesn't mean more than saying historical movement is determined by
economics "in the last instance" -- and if you're looking for a clearer
relationship than that, there is the possibility of evolutionary
explanations
that are not scientifically air-tight and politically obfuscatory to boot.

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> http://evolution.berkeley.edu/evolibrary/news/060201_zebrafish
>
>
> But how did different ethnic groups wind up with these different
> versions of the pigmentation gene? Research suggests that more than
> 100,000 years ago, the earliest humans lived in Africa and carried
> the "G" allele, which causes lots of melanin to be present in skin
> cells and hence, dark skin. Melanin absorbs UV rays from the sun and
> controls the amount of UV radiation that penetrates our skin. Our
> bodies need some UV radiation (to build the essential vitamin,
> vitamin D) but not too much (because UV radiation can damage the skin
> and destroy another essential vitamin, folate). In the sun-drenched
> environs of Africa, dark skin was advantageous, preventing UV rays
> from doing too much damage, while allowing in enough UV to synthesize
> vitamin D. In that environment, individuals born with a mutant
> version of the gene associated with less melanin and lighter skin
> would probably have had poor health and low reproductive success.



Many biologists hypothesize that between 55,000 and 85,000 years ago,
> humans began to migrate out of Africa. Some of them wound up living
> in the colder, darker climes of Europe. There, too much UV radiation
> was not a problem, but too little UV to synthesize vitamin D probably
> was. At some point either before or after the migration out of
> Africa, a mutation occurred in one of the ancestors of modern
> Europeans. This mutation was tiny, changing just a single base, but
> it caused much less melanin to be present in the skin of those who
> carried the mutation. This was the "A" allele. Among the new
> Europeans, this allele likely had an advantage over the "G" allele.
> Individuals carrying the "A" allele had less melanin, which allowed
> more UV light to penetrate their skin, which could have allowed them
> to synthesize vitamin D better than those carrying only the "G"
> allele. These "A"-carrying individuals had increased reproductive
> success in their sun-poor environment, and via natural selection, the
> "A" allele spread throughout the European population. Meanwhile,
> among Africans, the "G" allele continued to be advantageous and to
> maintain its majority there.The discovery of this pigmentation gene
> has helped us piece together a more complete picture of the
> evolutionary changes that underlie skin color differences between
> human ethnic groups. It suggests that a great deal of the skin color
> difference that has delineated the boundaries of social tensions for
> much of recorded history can be traced back to a tiny genetic change
> that allowed humans to better survive and reproduce in particular
> environments.


Is this plausible? Sure. But you've also had an expert on this list
hypothesize another mechanism for the development of light skin.
Furthermore, the idea that dark-skinned people are constitutionally
unfit for life at northern latitudes has not historically been an
innocent, "unpolitical" observation. If the practical consequences
of this are just that black people living above the 30th parallel
should take Vitamin D supplements, I see no problem: but this
sort of reasoning can and sometimes is multiplied indefinitely to
cover any sort of social phenomenon, with no such restriction.

Really, I didn't think that the idea that Social Darwinism is
contrary to historical materialism would be controversial here,
but I guess that people concerned with being "naturalistic"
sometimes discount the ideological character of some
evolutionary discourse. I will put Gould's *The Structure of
Evolutionary Theory* on my reading list, but I still don't
think E.O. Wilson is coming to the rally, folks.