Gene Expression

As you mentioned in your previous post on this topic, there were agricultural areas in the Americas, agricultural areas responsible for much of the food we eat today. You wondered in the last post if maybe Native Americans remained dark skinned because they didn't move as exclusively to a plant-based diet as Europeans presumably did. I know that in the main centers of American plant domestication, Mesoamerica and the Andes, a vast array of plant types were grown, a variety of plants which I suspect dwarfs that of the Fertile Crescent and Europe. This could have contributed to better nutrition. Outside of those areas, there was not a clear switch to exclusive reliance on agriculture. In almost all regions of the Americas where there was agriculture, it was supplemental, with wild plant gathering and hunting continuing even in the Mesoamerican and Andean cradles of American plant husbandry, even when populations were large. This is partly because of cultural differences from Indoeuropeans that resulted in preservation of much of the natural environment (I realize that Native Americans didn't leave their environment undisturbed, but we can't ignore that a great deal more of the natural environment was preserved by them than by Europeans in their home territory, even where population sizes were equivalent).

What about high latitudes of Australia? They are equivalent to southern Europe, where people are typically of a European lightness, yet aboriginal Australians are as dark as Africans and they've been there for 40,000+ years. And what about high altitudes throughout the world, many of whose indigenous populations remained dark skinned? Are issues of altitude similar to issues of latitude on this topic?

The timing-of-human-hair-loss post you linked to in a recent post also raises an issue. The human populations with the most body hair are Europeans/Indoeuropeans/Semitic peoples and Japan's indigenous Ainu, yet Europeans are some of the lightest-skinned people of all. Are there theories about this?

I'm not a geneticist so my thoughts may not be worth much here, but I always think that light skins developed in Europeans/Indoeuropeans and some East Asians as aberrations, with little relation to latitude or diet. They survived because they weren't harmful (and in the case of Europeans/Indoeuropeans, because their bearers were quite aggressive) but otherwise they're merely limited regional variations. I'm hoping to learn more, though.

Posted by: deang | January 25, 2008 2:04 AM

Interesting you lead with a picture of bread made from wheat. Northern Europeans may have been eating cereals, but not wheat. Even now wheat is not much grown in the more northerly areas of Europe. Rye and oats and barley were the main cereal crops, being more resistant to wet and cold.

In the Americas agriculture was confined to the south until fairly recently, meaning hundreds, not thousands of years ago. The strong sunlight would have prevented any pressure towards lighter skin. In the north agriculture was more limited. I have read that the Mississipian cultures were heavily dependant on corn, but they were wiped out by disease soon after Europeans appeared, so we know little about them, and nothing about their skin color.

As for the first comment, that Europeans were more aggressive than others. Well, look at history. Only in the last few centuries have Europeans been pushing east. The push was mainly from the East to the West in most of known history, Alexander the Great excepted, and he managed only one short-lived invasian of India. Think Huns, Turks etc. Indo-European-speaking peoples were present in China at one time, but disappeared.

All human groups seem aggressive when given the opportunity.

Posted by: tom bri | January 26, 2008 3:31 AM

the only comment I have to make,
a clarification really, is that it does seem to me that neanderthals and homosapiens interbred. It is more likely that the MC1R gene was passed rather then evolved over such a short duration in homosapiens. It is too cooincidental that a gene that is so very advantageous and necessary just spontaneously appeared during a period that both lived simultaneously in the same geographic area. You add this to the fact that MC1R is nearly identical to that of Neanderthals and...I think you gete my point

Posted by: Mikie | January 29, 2008 9:07 PM

Hey Razib, a lot of the studies are about development of light skin, but I am yet to find out anything about the development of dark skin amongst us. When did the gene for melanin production evolve? Did our pre-homo-sapien-sapien hominid ancestors already have the melanin, and is that why we always presume a journey of dark to light in terms of evolution? To me it seems like the jet-black skin of the sub-Saharan Africans and many throughout the Indian subcontinent happened later from an originally lighter/brownish stock.

Posted by: U Saxena | February 24, 2009 12:13 PM