I've seen some mtDNA studies I'd like to believe, mostly tracing isolated populations of Jews (Ethopian, Indian, etc.) back to ancient Israel, but I don't think I've ever seen a study that didn't prove what the investigator was hoping to prove, so I'm somewhat skeptical.

I understood that the explanation for increasingly pale northern peoples lay in the body's need for Vitamin D (or whichever vitamin it is that the body needs sunlight to synthesize). The farther north early humans got, the more oblique the sun's rays became, and thus the solar radiation they were exposed to becamse less intense. In the weaker sunlight, paleness helps the body manufacture the vitamin D it needs by allowing deeper penetration by the neccessary part of sunlight's spectrum.

The Inuits, I guess, got up north much later than the Scandanavians. Etc., etc.

Twn:
The body requires sunlight to produce vitamin D. However, the obliqueness of the sun's rays is only part of the equation.

Cloud cover is the rest. Northern Europe is probably the cloudiest area on the planet.

Jeff:

That makes sense, but do you believe black-skinned Africans migrated to Scandinavia and developed white skin to get more vitamin D? If so, why the blue eyes? If not, what other explanations can you think of?

Peter:

Well, they didn't get there overnight. They didn't "develop" white skin to get more Vitamin-D. Rather, there was some distribution of skin color across the population, and as people gradually moved into those areas, those on the lighter end of the bell curve were less likely to develop Vitamin-D deficiency. Therefore, they were statistically slightly more likely to leave offspring.

Heck, I don't have a clue about the why behind blue eyes.

BTW--how was your skiing holiday?

Jeff:

Great, thanks, but frigid. No cold gene in this Canadian!

I know you think I am baiting you, but I'm just trying to find a story that makes sense. Are you saying blacks and whites both used to roam Scandinavia but the blacks all died off because it was too cloudy?

Also, why did everybody migrate from East Africa to such awful climes? Why didn't anybody migrate back, especially if they were all dying off in Northern Europe?

Peter:

I'm saying "blacks" never made it to Scandinavia. It took a long time to make the move from Africa into Northern Europe. By the time people made it to Scandinavia, there were no blacks, but there was a climatalogical correlation between melanin concentration and climate.

People then, I am guessing, found it easier to migrate to where people arent, then to where they are. Also, any given generation was likely to migrate just far enough to find a suitable empty territory, which probably wouldn't look very much different than what they were already used to. I can't remember for sure, but I think archeologists believe it took roughly 5,000 years for people to migrate from Alaska to Tierra del Fuego. That is only about 40 miles per generation.

Jeff:

Have you ever considered how implausible is the idea that a given people would stay on the move in the same direction for forty generations? That trumps Exodus and no one ever suggested that was plausible or common or natural. How come pre-history is full of people migrating fantastic distances (often away from temperate and into hostile climates) but then they generally start to settle down when recorded history starts? (And if you say scarce game, you are making huge leaps of faith about relative human/animal populations, are you not?)

You know, like others, I am often struck by the general chronological accuracy from an evolutionary point of view of the story of Creation in Genecis. Quite unlike any other mythical cosmological history I have ever heard. The more I get into this with you, the more I see suspicious parallels with the whole Pentateuch.

mtDNA studies tell us, surprisingly, that Africans did not just walk north. They came out via the Red Sea and marched coastwise. Some ended in Australia, others in east Asia. Europe appears to have been people from the east not the south, and comparatively late. (There were, of course, premoderns humans there earlier, but we cannot do mtDNA traces to recreate their wanderings.)

If you look at a map of blondness frequencies, it is obvious where the mutation occurred -- Lithuania. The frequency diminishes uniformly in all directions from there.

Peter's question about wanderings is a good one, but there was still a lot of wandering going on in historic times. In N. America, the moves of the Tuscarora were epic.

Peter:

How do ripples move?

Put differently, nature abhors a vacuum. Think about how the US evolved: essentially uniform direction in the direction of the remaining vacuum--the Native Americans failed to exert enough counterpressure.

People didn't move from temperate to harsh climates. They followed the path of least resistance from where ever they were to someplace very much like it. 40 miles/generation scarcely covers the distance from my house to my office.

Harry/Jeff:

Look, the problem is your quantum jumps from general observations to full-blown detailed history. Obviously there are connections between climate and skin-colour, but there are a lot of exceptions too (Why do Middle-Easterners have lighter skins than African jungle dwellers? They suffer a lot more direct sun). Ditto for nomadic movements, which obviously occurred. But you guys seem to have everybody in perpetual long distance travel to set up the mutations. Does this mean man is now going to stop mutating if we all stay close to home? Are you really confident you are playing skeptical scientist here and not sqeezing the evidence into the theory?

Harry, how does one take a coastal route from the Red Sea to Lithuania for the gene makeover? Via Spain? Everybody passed through Lithuania? It must be a paleontologist's heaven. (Is it?) North American Indians may have ranged far and wide, but Alaska to Tierra del Fuego? I know precious little about this, but I have seen Inuit migration patterns and they seem to have spent a lot of time travelling in circles and never left the Arctic.

Europe was settled from the east. The mutation arose in Lithuania. What is so difficult to understand about that?

In the US westward movement, people strongly tended to move on along the same latitude they started from -- Tennesseans went to Texas, Ohioans to Iowa. We don't expect a genetic or darwinian explanation for that. People behave like people.

Europe was settled from the east. The mutation arose in Lithuania. What is so difficult to understand about that?

In the US westward movement, people strongly tended to move on along the same latitude they started from -- Tennesseans went to Texas, Ohioans to Iowa. We don't expect a genetic or darwinian explanation for that. People behave like people.

Harry:

Tennesseans went to Texas as individuals in response to conscious desires, not collectively to survive. Did they mutate as they passed through Arkansas?

Peter:

Your exceptions aren't really exceptions, but rather variations within a type.

Finding light skinned, blue-eyed, blond natives in equatorial regions would be an exception. There aren't any of those.

I'll bet if you looked at bacterial migration patterns in agar, and human migration patterns on a map, a great many similarities would arise. Among them that migration tends to be radial--as Harry noted--rather than lateral. Radial is the path of least resistance.

And not all members of a population migrate. Of the first inhabitants of Alaska who remained behind, what reason was there to go anywhere?

Jeff:

What is the difference between an exception and a variation?

Bingo, Peter. Only occasionally do whole populations move. Individuals or families go to Texas. If Texas is empty, they multiply greatly.

So, for example, there are more English speakers in America than in England. David Hackett Fischer has a great deal about the tremendous population explosion of the early English colonists in, say, Delaware in "Albion's Seed.'

Peter:

In general, at any given latitude, people have darker skins than at a more northerly latitude. Skin color is not identical at any given latitude; Yemenis are lighter skinned than Africans. But all Yeminis and all Africans are darker skinned than Italians.

That is variation.

An exception would be a discontinuity in the variation. Finding very dark skinned people in a northerly latitude, in contrast to the otherwise observed variation, is an exception. Finding dark skinned people in an area with limited sunlight, or light skinned people in an area with extensive sunlight, would also be an exception.

There may very well be some of those, but none to my very limited knowledge.