Talk:Human skin color

What about the new theory that melanin is an anti-infection agent and that rather than people evolving lower melanin in order to let in more light, they did it because they weren't as healthy and so couldn't afford the metabolic cost of melanin production? According to this theory, melanin corresponds to humidity levels (which many viruses and bacteria depend on) instead of light levels. --Ark

Hum, -- never came up in my immunology, antomomy or human evolution classes and I can't find anything (http://www.google.com/search?q=melanin+humidity+infection+%22skin+color++%22&hl=en&lr=&as_qdr=all&start=20&sa=N) about it on Google either. It does sound interesting. Do you have a webpage or better yet a peer-reviewed journal article to point me to for more information? --maveric149, Tuesday, June 11, 2002

Heh. It came up either in Scientific American or New Scientist. Probably sometime in the last year. In the last two years definitely. :)

Basically it was speculation based on some preliminary finding. I don't remember what the finding was though. I just mentioned it because like you said, it's so interesting. -- Ark

Cool I try to find it. It's probably a bit too new and unvarified to include in this article though. --maveric149

What does this mean?

In general, people with recent ancestors in sunny regions have darker skin than people with recent ancestors in regions that lack much sunlight.

Was the above sentence intended to support idea that acquired characteristics can be inherited? I thought Lysenkoism had been thoroughly discredited. --Ed Poor 19:59 Sep 6, 2002 (UCT)

I think you can get that with usual natural selection arguments. White skin is more susceptible to skin cancer, so you could eliminate them from the gene pool because of that.AstroNomer (Who is not a biologist and is just waving hands)

• I also am not a biologist. However, my understanding is:
  • If you are born light-skinned in a region with intense sunlight levels, your chances of skin cancer are much greater. Ergo genes for fair skin are much less likely to be passed on. There are probably other factors like increased vulnerability to disease as a result that would intensify this.
  • If you are born dark-skinned in a region with low sunlight levels, your body doesn't synthesize as much of a certain nutrient (vitamin D?), which is best catalyzed by sunlight on skin. Ergo, your resistance to disease and such goes down, and again, your genes are far less likely to be passed down through the generations.
• Over many generations this dual selection effect may lead to the grouping of prevalent skin colors according to the amount of sunlight received by, oh, the past few hundred generations in a given locale. -- April

Right, I understand about the "genes being passed on" part. And it accords with ethnographical observations of Northern Europeans being light-skinned and equatorial Africans and Caribbeanns being dark-skinned.

My confusion was about the "recent ancestors" claim in the sentence I first quoted way above. I'd like to revise it so it doesn't give the impression that the process takes place over a couple of generations. Doesn't it take centuries before we start to see any significant differences? --Ed Poor

I see what you mean. Probably he was meaning e.g. african-americans: they have "recent ancestors" from Africa, that were dark skinned because they had had lots of ancestors living there. There is a step missing in the chain.AstroNomer

• Going out on a limb here, with my shaky bio knowledge, but I'd guess that the genes for most skin levels would be present, if not common or commonly expressed, in just about any population. So if two groups of humans colonize a high-sunlight planet and a low-sunlight planet, and then are cut off from intermarriage outside the group, we'd start seeing significant changes between the populations in... well, if you take a "generation" as about 20 years... at a very rough guess, maybe a few centuries?

• I suspect that by "recent" the person was thinking "hundreds or thousands of years in the same place" as opposed to, say, ten thousand to a hundred thousand years, which is (I think) the scale of many major population migrations. Add a lot of caveats that I could be talking complete nonsense here, 'cause I'm far from expert. :) -- April

I thought of "recent ancestors" as not more than 4 generations back, like my great-great-grandparents, who are Polish and Russian Jews (on my mother's side). Thanks for the scientific help. I think I have enough information to edit the article.

What means "The lighter skin of women results either from sexual preference or from the higher calcium needs of women during pregnancy and lactation."??? Can I see the ``sexual preference of a woman in her skin color?

  -M

Why/how is it that the Tasmanian Aborigine, a population isolated for thousands of years so far south, retained such dark skin? Tasmania is as close to the South Pole as Southern Europe, mid-North-America, or Japan is from the North, and the populations of those areas were much lighter. -- stewacide 20:39, 18 Mar 2004 (UTC)

I'm a tad confused as well. For vitamin D production, the amount of time spent in the sun is trivial -- say, about 15 minutes/day, for a light-skinned person. For a dark skin person, they might need 6 times that -- Say, an hour and a half. Thus, the skin-color/vitamin D link seems a tad weak. I believe Darwin wanted to chalk skin color up to sexual selection. The Tasmanians have been isolated in Tasmania for thousands of years -- the disappearance of the Tasmanian-Australia landbridge is known. At the same time, the retreat of the glaciers from northern Europe happened later. But the typical northern European has light skin, Tasmanians have dark skin.

van Luschan scale

Felix von Luschan, (1854-1924)

In anthropology, verbal descriptions of skin colors ("white," "yellow," "black," "brown," and "red") were replaced by color-matching methods during the early twentieth century (Olivier 1960, von Luschan 1897). The most popular of these methods was the von Luschan scale, based on the use of colored tablets or tiles of different colors and hues with which the colors of unexposed skin were matched. These and similar matching methods could not be consistently reproduced, however, and were swiftly abandoned when reflectance spectrophotometry was introduced in the early 1950s

[1] (http://arjournals.annualreviews.org/doi/full/10.1146/annurev.anthro.33.070203.143955?cookieSet=1) dab 11:55, 28 Nov 2004 (UTC)

Eyes color

Any information about the human eyes color?

Cutting two dubious "See also" links

, History, Tom Irwin.

The above two links were inserted by User:80.46.154.123 at this edit (http://en.wikipedia.org/w/wiki.phtml?title=Human_skin_color&diff=2900857&oldid=2613886). Going out of my way to assume that this prank was done in Good faith, I am leaving this record for someone to revert if generic History and "Tom Irwin" are renowned experts in Skin color that I cannot find in Google. 8)) ---Rednblu | Talk 19:10, 22 Dec 2004 (UTC)

latitude

it seems strange to say that skin colour is not correlated to latitude but rather to the amount of UV radiation, since clearly the latter is correlated to the former. dab (ᛏ) 19:50, 22 Dec 2004 (UTC)

• For example, if you look at the map, natives to Africa have much darker skin than natives to South America at the same latitudes. That is because there is much more cloud cover over South America than over Africa. Good suggestion!  :) I will add an explanatory note to the caption to make your point clear. ---Rednblu | Talk 23:04, 22 Dec 2004 (UTC)

You'll need an entire subsection soon. But I don't agree with your interpretation. Note that the "natives" of South America immigrated some 20k years ago, the Australians some 70k years ago, while the Africans were in Africa "forever". So even if there was as much Sun in South America as in Africa, people may not have been there long enough to adapt. Your explanation is simplistic, as if humans were uniformly distributed on the Earth at one time and then started to adapt. Human migration is at least as important a factor for explaining the patterns. e.g. the pink corner in South Africa is not due to a permanent cloud-cover, but almost certainly to inter-marriage with immigrants. dab (ᛏ) 08:47, 23 Dec 2004 (UTC)

• That's all right. You missed the Jablonski 2000 article. [2] (http://www.bgsu.edu/departments/chem/faculty/leontis/chem447/PDF_files/Jablonski_skin_color_2000.pdf) No big deal. 8)) The adaptation takes place in a few thousand years. And the data is only for "Natives" who have been relatively fixed for a thousand years. No intermarriage is in the data. You can compare the raw data in the tables at the back of the Jablonski article to the map. ---Rednblu | Talk 12:16, 23 Dec 2004 (UTC)

interesting. although I find it hard to believe. this borders on Lamarckism. Do you mean the map on page 77? I'm sorry. I am not an expert, but I suppose unless the data is cross-referenced to genetic analysis (mitochondrial etc.), the matching of skin shade to latitude is rather pointless. You would have to show that adaptation is quicker than migration, eg. for South Africa. Do they say somewhere that South Americans are lighter because there is less UV there than on similar latitudes in Africa? Anyway, I don't have the time to dig into this right now, so I just assume you are right. dab (ᛏ) 14:54, 23 Dec 2004 (UTC)

also, your caption is suggestive that the map should be taken at face value. While it is of course good enough to give a general idea, I was very careful to state on the Image page that it is outdated, and should not be used as an up-to-date reference. dab (ᛏ) 08:51, 23 Dec 2004 (UTC)

The inuit are probably a poor example, since high latitudes have alternating patterns of extremely high (or at least constant) sunlight followed by almost none. so far the adaptations i'd heard of included the narrow eyes.. though now that i think of it, that's universal mongoloid, so that makes no sense. anyway, i've never seen a 'relatively dark' inuit, so that part doesn't make sense to me.