Palm and Sole coloration on Africans...why?

First, I posted this message already, but imbedded in the “Races” thread, which doesn’t seem to be read very much, so there’s not much chance of it getting answered there:
Why are the palms and soles of Africans colored like the skin of Caucasians? At first I figured it had to do with the sun and melanin and everything, but then I realised that Africans’ armpits and nether-regions aren’t colored in this way. That kind of eliminates the sun theory, in my mind, because these areas don’t get much daylight, either. So, why are their palms and soles colored like that?

The same phenom. exists in white people. The contrast in darker skinned people is greater, is all. Look at someone who is tanned.
I assume that it has something to do with the lack of melanin in these areas.

Probably related, though I’m not sure how: The soles of your feet and the palms of your hands are the two parts of your body which have the most physical contact with the rest of the world. Maybe excessive contact isn’t conducive to melanin, somehow? (surely it doesn’t just “rub off”?) These are also, so far as I know, the only spots on the body which are completely devoid of all hair.

Because when God spray painted them he had them spread out on a wall (like cops doing a bust). :smiley:

This joke courtesy of Eddie Murphy.

I’m afraid I can’t figure out why I think this, but I believe it’s partly due to the fact that the skin on our palms and soles is very thin. (Obviously, foot skin thickens up, but that’s due to callouses, which don’t have any pigmentation) This, combined with the huge number of nerve cells in these areas, means there’s just not a lot of room for pigment-producing cells.

I may be wrong, in which case someone will correct me.

the eyelids of black people are black.

i was talking to my friend ken (kemijo on this very board), and his theory was that it comes from the fact that we used to walk on our hands and feet.

it was mentioned by someone before that white people have the same thing, but for obvious reasons you don’t see it.

Common though, it’s not like that’s the only different thing about those parts of your body. Where else on your body does your skin make unique spirals? Where else do you have permanent folds in your skin? Besides, what animal has hair on their palms or feet? I say pigment-producing cells were an advancement we just didn’t need everywhere.

Another point is that the coloring between the races is the same; it’s just the amount of pigment that varies.

From Integumentary System
"1. Cells of the epidermis (Fig.5.2) :
(a). keratinocyte (90%): synthesizes the protein ‘keratin’ for water-proofing
(i). arises in deep epidermis
(ii). takes 28-40 days to mature, then dies and appears scale-like at outer surface of skin
(b). melanocyte (8%): synthesize the pigment 'melanin’® absorbs UV light and is responsible for skin color
(i). found at the base of the epidermis
(ii). transfers melanin onto the free surface of the keratinocyte
©. remaining 2%:
(i). Langerhan cell- macrophage
(ii). Merkel cell- associated with sensory nerves, specifically touch

2.Five Layers of the Epidermis (Fig.s 51; 2) (from superficial® deep) :
(a). Stratum Corneum- 25-30 layers of dead, flat, anuclear, keratinized epithelial cells
(b). Stratum Lucidum- 3-5 layers of dead, flat, transparent epithelium;
ONLY found in the palms and soles
©. Stratum Granulosum- 3-5 layers of flat, granular cells; keratin is hardening;
nuclei/cells are dying
(d). Stratum Spinosum- 8-10 layers of round/cuboidal-like cells with a central nucleus; cells are living; keratin is being synthesized
(e). Stratum Basale (basal cell layer)- a single row of cuboidal/columnar cells
undergoing mitosis"

And finally and MOST importantly check out Carotene…

"E. Skin Color- a result of 3 pigments:

  1. Melanin- pigment derived from the amino acid tyrosine (albinos lack tyrosine)
    (a).all races have an equal # of melanocytes
    (b).variations in color are due to the differences in the amount of melanin produced
    ©.protects skin from UV light
  2. Carotene- yellow pigment
    (a). increased concentrations of carotene found in the palms and soles
    (b). Asian skin color due to variations of melanin, NOT carotene
  3. Hemoglobin- O2-carrying pigment in bl. vessels; reflected through the avascular epidermis"

It looks like it is a result of the increased concentrations of carotene in the palms and soles though it could also be affected by the Stratum Lucidem

Related question: is it possible for naturally pigmented persons to lose pigmentation in a body part. The reason I ask is that I dated for years a Filipino woman. While she wasn’t extremely dark, and her coloration changed somewhat depending on whether she was spending much time in the sun, she alway had a good amount of pigmentation.
Except for her, ahem, breasts. They were white as the driven snow. And very … oops, we’re in GD.
We joked about it a lot, but we never really tried to uncover the answer. Any thoughts?