October 12, 2007

Pink palms

Here's a question that everybody has wondered about at least once since they were six years old, but I've never heard an answer for: why do black people have pink palms and soles? Is it also true of other darkskinned peoples like Melanesians?

My published articles are archived at iSteve.com -- Steve Sailer

35 comments:

Anonymous said...

My speculation is that this has something to do with producing Vitamin D:while having a dark skin may protect you from skin cancer, melatonin also inhibits the production of the essential vitamin.

Since palms are only exposed to sunlight on an intermittent basis, the risk of developing cancer is much less; hence the marginal benefit of extra protection is outweighed by the benefits.(Which, ironically, include protection from cancer).

Art De Vany had longish,but interesting post on skin pigment, Vitamin D and cancer here:

http://www.arthurdevany.com/2005/05/suntans_and_mea_1.html

Anonymous said...

Black IQs are "skyrocketing" -- in case you hadn't heard.

eh

Grumpy Old Man said...

I would imagine for the same reason that cave fish are blind--there's no reason for the body to expend effort producing melanin for parts of the body that aren't exposed to the sun.

That's just a guess, though.

Anonymous said...

Even light skinned people can't tan on the bottom of their feet or the palms of their hands. I'm more curious about ears. My ears don't tan but dark skinned people don't have pink ears. Why don't my ears tan? They don't match the rest of me in the summer.

Peewee said...

I believe so. I know Australian aboriginals at least have light-colored palms. I've been looking at chimp pics and it's hard to tell. All of the chimps with light palms seem to have light faces too, but I cant be sure Im seeing them right.

The skin on our palms and soles is much thicker than elsewhere. I suspect this goes back to the days when we were all quadrupeds, and we needed a different and tougher kind of skin on our palms and feet to protect us from sharp objects on the ground. The absence of melanin is surprising though because melanin is good at protecting against minor scrapes, so I would expect those body parts to be the darkest of all. But maybe it doesn't work so well when the skin itself is thick, or maybe it just isn't needed. I would be interested in learning at what point melanocytes disappeared from the soles/palms of pre-humans, or if indeed it goes way back to before primates even evolved. If even hairy animals such as chimps have light palms (while having dark skin elsewhere) I dont think sun exposure could really be the reason, since the dark skin of the rest of their bodies wouldnt be exposed to the sun either.

tommy said...

I would imagine for the same reason that cave fish are blind--there's no reason for the body to expend effort producing melanin for parts of the body that aren't exposed to the sun.

I would second that. Chimpanzees are not dark-skinned after all.

SFG said...

Hey Steve, offtopic: you've stated that Africa, in part because women are able to generate income on their own, has a culture where men try to impress women as warriors, etc. Where did you read about this? Do you have a source where I can learn more?

Vol-in-Law said...

re 'black IQs are skyocketing':

Lindsey:
"It's time to shut up about the "low Black IQ", since by any reasonable standard, it is not low at all."

Lindsey is correct that 'the explosion in black pathology' since the 1960s can't be explained by the 15 point black-white IQ gap, since the gap is remarkably consistent while the fortunes of black and white populations have diverged markedly.

He's incorrect that a black IQ of 85 in 2007 is identical to a white IQ of 100 in 1945, since the Flynn effect has been concentrated in certain abilities - the 1945 median white will be better in some areas of cognitive ability than the 2007 median black, and poorer in others.

He's incorrect that the US black IQ is not 'low by any reasonable standard' - it's only about 5 points below the global median IQ, but it is, of course, still 15 points/1 SD below the median US white IQ; thus only about 1/6 of US blacks are smarter than the average US white, whereas 3/6 of US whites are smarter than the average white. That has societal import.

Furthermore, while US median black IQ is only slightly below global median IQ, it is likely that environment affects IQ and that the typical environment of US blacks, an advanced technological society, is more favourable to higher IQ than is the typical environment of most people in the world, given that most people don't live in advanced technological societies.

It's also notable that US black median IQ is about 15 points higher than genetically similar West African black populations. It's very unlikely that this difference is wholly genetic, since it's the same gap as is found between far more genetically dissimilar US white & black populations.

Rex said...

Black people do not have pink palms.

Anonymous said...

Most people don't expose their genitals a lot, either. Still, the genital area has melanin.

Fred said...

The skin on your palms and soles is significantly different from the rest of your skin in multiple ways. It is different in number of sweat glands, hair follicles, and thickness of layers of skin. My guess is that it the genes for palm skin don't completely overlap the genes for normal skin.

For example, my wife once burned her hand and her body developed a temporary allergic reaction to her palm and sole skin. She ended up shedding all her old layers of skin on her palms, soles, and the inner sides of her fingers and toes. Her doctor said that this reaction was not common, but not rare either.

Dark skin is selected for in humans in sunny climates due to our lack of hair protection for the overall body. I would surmise that when the mutation for dark skin happened in the genes for normal skin it was selected for by the sunny environment. But because extra melanin does not offer an advantage in your palm and soles, whenever a dark skin mutation appeared in someone's palm and sole skin genes, it was not selected for.

PatrickH said...

About Lindsay, I took a really brief glance at his post, and his problem seems to be that he thinks that the lack of validity for IQ tests for comparing across generations renders them invalid for making comparisons (e.g., between blacks and whites) within a given generation.

I'll take another look at the article when I have time, but it doesn't seem at first glance that he's got anything worthwhile. JMO, of course.

agnostic said...

The sunlight stuff doesn't make sense, since people have been wearing minimal clothing for awhile, and the groin and buttocks area isn't pink in Africans.

One common denominator is that the bottoms of your feet and palms of your hands are the conduits that physically connect you with the environment most directly -- walking on the ground, grasping and touching things, etc.

So, maybe lighter skin provides better grip / traction, or allows greater sensitivity to detect what the thing is (slimy, rough, sharp, etc.). Or maybe it's better at keeping out environmental insults like toxins or pathogens you might pick up by touching stuff. I don't know.

Svigor said...

I heard somewhere it had to do with sweat glands, but I have no idea one way or the other.

But, if it was about sunlight as two posters above suggest, then wouldn't that mean some of the sensitive bits up under the torso would be similarly melanin-free?

peewee said...

There are definitely dark-skinned chimps out there.
http://216.92.205.45/img/bonobo.jpg for example. They have just as much as range in skin color as we humans do. Which I find very interesting.

Bill said...

I think Fred's right. The genes are different, and not as much sun hits palms or soles, so the genes that adapt will be the ones affecting other types of skin.

It's pretty obvious that palm and sole skin are different from other skin. Do we have ridges like fingerprints anywhere else?

tommy said...

svigor,

I heard somewhere it had to do with sweat glands, but I have no idea one way or the other.

But, if it was about sunlight as two posters above suggest, then wouldn't that mean some of the sensitive bits up under the torso would be similarly melanin-free?


Well, I guess the theory goes that it would be a combination of the fact that genes encode for two separate types of skin: one on the palms and soles and the other on the rest of the body. If that's the case, then when the skin on your back is a certain pigment then the skin on your ass is going to be the same by default. But the question is why hasn't the skin on the palms and soles of African's hands and feet similarly darkened.

peewee,

There are definitely dark-skinned chimps out there.
http://216.92.205.45/img/bonobo.jpg for example. They have just as much as range in skin color as we humans do. Which I find very interesting.


That's interesting. I know that chimps sometimes have dark faces but I've heard that the skin color of chimps beneath their hair tends to be light. Do you know if the skin beneath the hair is similarly dark in these bonobos? It appears from your picture that may be the case, but I can't say for certain.

Peter Frost said...

Hey Steve, offtopic: you've stated that Africa, in part because women are able to generate income on their own, has a culture where men try to impress women as warriors, etc. Where did you read about this? Do you have a source where I can learn more?
-------------------------------

I've touched on this question in two of my posts:

http://evoandproud.blogspot.com/2006/12/skin-color-preference-in-sub-saharan.html
http://evoandproud.blogspot.com/2007/08/sexual-selection-and-human-phenotypic.html

Anonymous said...

I thought the answer was obvious: the color rubs off.

Peewee said...

Well Im pretty that particular bonobo there is bare-skinned in the front, and its skin is pretty dark. I wish I could tell you why it's so smooth-skinned, but I really dont know. But I've been reading around sites on the Internet and it's saying that within the same individual the skin color can vary quite a bit, more than the variation in a human individual save for the palms and soles. I just searched for "bonobo skin color", but the most helpful site of the bunch was www.honoluluzoo.org/chimpanzee.htm . If this post appears twice I made a mistake.

beowulf said...

"Mammals have specialized blood vessels in their palms and other hairless skin surfaces—ears, nose, cheeks and soles of the feet—that are designed to dissipate heat. (These radiator-like structures—venous plexuses and arteriovenous anastomoses—were described as early as 1858 in Gray’s Anatomy.) By redirecting blood away from the capillaries and into these blood vessels, the body can shed heat quickly."
http://tinyurl.com/84adp

Anonymous said...

his problem seems to be that he thinks that the lack of validity for IQ tests for comparing across generations renders them invalid for making comparisons (e.g., between blacks and whites) within a given generation.

He has a point here. The Flynn effect is indicative of the numerous problems with IQ as an attempt to operationalize the notion of "intelligence".

MQ

Mthson said...

The secret about the Flynn effect is that it's entirely unsurprising.

Studies suggest it has predominately occurred in the lower half of the population, fading from low to high.

In other words: yes, children going to school instead of working in coal mines improves their abstract cognitive ability.

Anonymous said...

Gorillas are dark-skinned and their palms are dark too. Both sides of their hands are identical.

I suspect early humans were light-skinned (like most chimps) and dark-skin is a later adaptation, perhaps to the sunny savannah after leaving the shady jungle.

Ben Capoeman said...

According to Jane Goodall, the chimpanzees she studied at Gombe are born light skinned, but turn dark skinned after puberty. I had the good fortune to take a primatology course taught by Birute Galdikas, another Leakey protege, who noted that orangutans have dark skin but are born with very light colored patches around their eyes and mouths which remain until adolescence.

Okay, I broke down and dug up an old text book, Great Ape Odyssey, by Dr. Galdikas. Orangutans and gorillas do not have noticably lighter skin on their palms or soles, with the exception of one photograph in which an adult female orangutan has mottled light and dark skin with a larger percentage of light on a palm than on her face. The chimpanzees pictured are split, some with light palms and/or soles, and some with uniform coloration. These chimpanzees are from different areas of Africa, and not always with notation saying which pictures are from where. The bonobos are identified as separate from the eastern chimpanzees.

If you've been reading John Hawks you'll know there's a bit of a kerfuffle concerning the dates of our assumed Last Common Ancestors, but in most current assumptions it's about 17 million years for orangutans, 9 for gorillas and 5 for chimpanzees.

Neither here nor there, but I think it interesting that Louis Leakey chose three women to run longitudinal studies of primates who so closely matched their subjects in personality. Goodall is curious and inquisitive and can be playful; Galdikas is quiet and solitary, with her first student of each class who assumes she's a pushover learning that she suffers fools not at all; and while I never had the opportunity to meet Diane Fossey everything I've been told of her enforces the image that she was direct and forceful, and would completely ignore people around her when her attention was engaged elsewhere - you didn't want to be the one to interrupt her train of thought, or to have her attention directed upon you were she to be disturbed.

Iosue Andreas said...

If I remember correctly, the Nuer people of Sudan, some of whom I worked with at a Chrsitian refugee resettlent agency, had plams the same color as the rest of their skin. And they were the darkest people I've ever encountered.

PatrickH said...

He has a point here. The Flynn effect is indicative of the numerous problems with IQ as an attempt to operationalize the notion of "intelligence".

No, he doesn't. And no it isn't. Not about the black-white IQ gap at any given time.

Lindsay's comparison of black IQs today with white IQs of 1945 is ridiculous. Why didn't he compare white IQs of today with black IQs of 1945? The difference would then have been enormous, and would have justified his article being titled The Skyrocketing White IQ.

Bill said...

You know, the funny thing is this seems like a childish question on the face of it, but it's actually a very good question. This is the case with a lot of mysteries.

This fact of pigmentation difference between palm and other skin leads to a lot of hypotheses in my mind.

Could it be, for example, that humans were originally light skinned, and that their skin darkened after they lost body hair?

Perhaps Eurasian light pigmentation is actually older than sub-Saharan hyper-melanism.

The most recent anthropological suggestion is that humans' and great apes' ancestors were bipedal, but some apes (gorillas, chimps, orangs) re-adapted to knuckle walking when they came out of the trees.

Couldn't it be possible that humans' ancestors were also fair-skinned, and then some of them developed darker skin as a result of emergence from the forest canopy and loss of hair?

Anonymous said...

Kind of a related question:
How come yellow labrador retrievers' noses turn from black as puppies to pink or reddish as adult dogs?

Anonymous said...

"Couldn't it be possible that humans' ancestors were also fair-skinned, and then some of them developed darker skin as a result of emergence from the forest canopy and loss of hair?"

Could be, bill. I can also guess where you are going with this. The idea has been put forward before but Afro-centrists seem to prefer the narrative that African's are the ancestors of all the other races. Still, following this logic, why don't light-skinned people from cold climates have a nice covering of warm fur?

CJ said...

I've seen lots of Melanesians -- in New Guinea, New Britain, and the Solomon Islands. Of course they have light-colored palms. Here's a pictorial example you can cut and paste into your location bar:

http://www.orders.anglican.org/mbh/Chapel.jpg

Bill said...

Still, following this logic, why don't light-skinned people from cold climates have a nice covering of warm fur?

-Anon


Well, we do have a bit more fur, actually. Maybe that would make another good question:

Why are white folks hairier?

Whites have plenty of archaic traits. Isn't it possible that our skin color is one of them?

Speaking of archaic, has anyone here a picture of that Russian boxer?

Nikolai Valuev

The above has to be one of the funniest boxing pics ever taken.

Thomas said...

Palms and soles are communication devices. Light skin flashes brighter than dark, particularly in dim light.

Follow a person walking or running barefoot. You can see the alternating flashes.

Virtually the entire human body is adapted in one way or another for communication.

Ben Capoeman said...

Thomas said "Virtually the entire human body is adapted in one way or another for communication."

That's true for all primate bodies. One species of baboon has moved into the savanna and adopted the practice of sitting down. This hides the color changes and swelling of the female genitalia during her periods of sexual receptiveness. So the females of this species lose the hair from their chests and the skin over their breastbones swells and discolors, allowing the males to be aware of their state of sexual receptiveness.

Study said...

On a different note about interesting observations- I don't know if its confirmed or not, but there seems to me to be an extraordinary high level of "alternate sexual lifestyles" in higher population areas such as big cities around the world. This isn't a judgment about it, just what I have observed. Is it that big cities are places where alternate lifestyle people can reach a "critical mass" of a community to publicly express their views, or is it that high population densities lead to more alternate individuals? Or an effect of both factors?

I do remember reading somewhere about a study with mice that showed that as significantly increasing population density in a mouse colony led to a sharp increase in mouse homosexuality, and agression. Something to think about in regards to ramping up our city populations.