Talk:Human skin color/Archives/2011/April

Claim that dark skin was the original human mode

There is no evidence that proves what skin color ancient Africans had. We just know they did not have the mutations present in Europeans for pale skin. They still had the capacity for a wide range of skin colors. We know that even in the heart of Africa we have populations referred to as Khoisanid who have some of the most ancient lineages and still were considerably lighter than Bantu populations. Furthermore, Bantu populations have also shown signs of skin color selectivity to get darker.

So skin color could have had a wide range in ancient Africa as it does today. Remember that those ancient Africans had to shed hair and progressively darken as they went from hairy apes to naked hominids. How dark they went would depend on area, time, diet, and environment. It is erroneous to assume all Africans went all the way to very dark skin and then some lightened back to somewhere in between. We just don't know at this time.

A letter I got confirming this by a geneticist who is studying genes and skin color

quote From: Heather Norton Sent: Friday, February 27, 2009 5:29 PM Subject: Re: Genetic Evidence for the Convergent Evolution of Light Skin in Europeans and East Asians

Thanks for your interest in my work. Before I get to your questions, I think that I need to clear up a bit of confusion about these pigmentation genes, particularly some confusion about the use of the terms gene and allele. First, yes, these genes exist in other primates. That is to say, primates have stretches of DNA sequence that produce the same protein in humans and in chimps, and these are usually found in the same corresponding region on their chromosomes. So, it would be correct to say that both humans and chimps, for example, have the gene for ASIP, OCA2, MC1R, etc. When we look at the sequence of individual nucleotides (A, C, G, or T) that make up a particular gene, we may see small differences between chimps and humans. So, for example, at one place in the OCA2 gene chimps might all have a G base, where humans all carry an A in the corresponding position. This is what is known as a fixed difference, and studying fixed differences may help us to understand why humans and chimps differ for certain traits. However, you can imagine that there may be other cases were chimps carry a G at a certain position while some humans carry the G and others carry an A. When we see the same nucleotide being carried in both species (in this case, the G) we call it the ancestral allele. When the nucleotide differs (in this case, the A) we refer to it as the derived allele. The term allele here is used to refer to a different versions of the same gene. So, while chimps and humans have the same pigmentation genes (so do mice, and pigs, and fish), they may carry slightly different versions of that gene. Sometimes we see slightly different versions of a gene within the same species. These different versions may explain some of the physical differences (like skin pigmentation) that we see among individuals. In other cases, though, these differences dont affect the protein that the gene produces, and so they dont seem to explain physical differences. So, onto your questions. The question of the San and Sandawe is an interesting one. We are not sure if the alleles that explain why their pigmentation is so different from neighboring populations reflect new (derived) mutations or if instead maybe they are actually ancestral alleles shared with light-skinned primates. I would say that this is an area of open investigation. As for ASIP and OCA2I think that even if you ignored the contribution of these two genes to pigmentation variation we would still see good range of diversity. For example, genes like SLC24A5 and MATP also have a major impact on phenotype. I would also assume that in the past there was variation in human skin color. It would be unlikely to be as much variation as we see across the human species today, since today modern humans live in a range of environments where different pigmentation types are more or less adaptive. In general, I would say that the pigmentation of early humans, who originated in Africa, was dark to provide protection against the damage that ultraviolet radiation can do. However, when we look at populations in Africa today (or populations living in other places where ultraviolet radiation is strong) we see a wide range of variation in pigmentation. I suspect that if we could go back in time we would probably see similar levels of diversity to those that we see in Africa today. end quote.

In other words, there is no evidence to indicate that the huge variation of skin color already existent in Africa wasn't always there.

This is a South African San: http://www.nma.gov.au/shared/libraries/images/temporary_exhibitions/extremes/extremes_large/africa/a_khoisan_man_northern_cape_south_africa/files/6398/nma.img-ex20042116-262-vi-vs1.jpg

Now the earliest skull we have found is in Ethiopia. But human remains are notorious for not surviving in many environments.

Sarah Tishkoff just finished her decades long DNA study. It turns out that the San bushmen of southern Africa have the most distinct, and therefore oldest, genetic sequences.

Then also consider that the mostly disappeared Bisa Sandawe of Tanzania were markedly lighter than their Bantu neighbors. JCTrevor reported this in 1947, So did Ten Raa. I confirmed this with Imogene Lim, a Japanese anthropologist who lived among them:

quote From: Imogene Lim Sent: Tuesday, July 29, 2008 8:17 PM Subject: RE: Rock-shelter Use Today: An Indicator of Usandawe Prehistory

If you look at recent photographs, there has been increasing intermarriage between groups. Certainly when I conducted my field work some 20 years ago, there were those who shared strong resemblance to their southern counterparts, the Ju/hoansi and other Bushmen/San, the only other true Khoisan language speakers. After being in the field over a year, I was darker in skin tone than many of the Sandawe in the community where I lived.

Eric Ten Raa who studied among the Sandawe in the early 1960s has photographs in one particular article showing the distinction between the Tehla and Bisa Sandawe. If you have done your reading, you will know that the latter are the ones who exhibit the classic Sandawe phenotype. end quote

This is Imogene Lim. http://www.viu.ca/images/portraits/limi.jpg

So a tanned Japanese woman could be darker than some Africans. Africans with some of the oldest genetic markers in existence. It just goes to show you the huge variety already in Africa. To assume the earliest Africans were as dark as Bantu populations, when we have populations like that of the San, is just that, an assumption. We do not have clear evidence to make such a claim. --Salsassin (talk) 17:49, 8 May 2009 (UTC)

Excellent contribution. Thanks! The question of the San definitely puts a different spin on things... Succubus MacAstaroth (talk) 10:28, 1 April 2011 (UTC)

Orphaned references in Human skin color

I check pages listed in Category:Pages with incorrect ref formatting to try to fix reference errors. One of the things I do is look for content for orphaned references in wikilinked articles. I have found content for some of Human skin color's orphans, the problem is that I found more than one version. I can't determine which (if any) is correct for this article, so I am asking for a sentient editor to look it over and copy the correct ref content into this article.

Reference named "Agar2005":

• From Melanin: Agar N, Young AR (2005). "Melanogenesis: a photoprotective response to DNA damage?". Mutation research. 571 (1–2): 121–32. doi:10.1016/j.mrfmmm.2004.11.016. PMID 15748643. {{cite journal}}: Unknown parameter |month= ignored (help)
• From Sun tanning: Nita Agar; Antony R. Young (2005). "Review: Melanogenesis: a photoprotective response to DNA damage?". Mutation Research/Fundamental and Molecular Mechanisms of Mutagenesis. 571 (1–2): 121–132. doi:10.1016/j.mrfmmm.2004.11.016. PMID 15748643.{{cite journal}}: CS1 maint: multiple names: authors list (link)

I apologize if any of the above are effectively identical; I am just a simple computer program, so I can't determine whether minor differences are significant or not. AnomieBOT⚡ 11:43, 5 April 2011 (UTC)

Now fixed. --Avenue (talk) 03:13, 22 April 2011 (UTC)

On speciation

Homo sapiens developed in its present form around 200,000 years BP according to DNA evidence. The earliest skeletal material, from Omo Kibish, Ethiopia, is dated at about 140,000-130,000 BP (From Lucy to Language 1999). It is therefore evident that the speciation of H. sapiens had nothing to do with the skin color variation gene around 1.2 million years BP. Anyway H. neanderthalensis also ought to have had a lighter skin color, living in Europe in the period 240,000-28,000 BP. There are thus several unexplained lapses in the article. —Preceding unsigned comment added by 85.233.248.215 (talk) 19:39, 26 April 2011 (UTC)