I found this to be a fascinating question, but Cecil’s response…excuse the blasphemy, wasn’t great.
The reasoning seems to be: in Brazil people find lighter skin more attractive. Therefore “some people” think that eventually there’ll be some pink people, lots of coffee-coloured and few dark-skinned people.
There are a few problems with this analysis:
The question was about all humans. In the world as a whole different skin colours are still largely geographically clustered.
How can the average skin lightness of a population go up just from mating choice? For the average to go up surely you would also need more reproduction to be happening among the lighter-skinned people.
When is “eventually”? And is this the equilibrium state or with further lightening occur?
I’m not a population biologist, and I find it difficult to predict what will happen to the “races” long-term. I can’t help naively looking at the picture as like two tins of paint, one black, one white. No matter how little mixing of the two tins occurs, eventually two tins of grey paint will result. Somehow I suspect this analogy may be over-simplifying a tad…
I suppose we could also discuss the different birth rates in different parts of the world. It used to be a “well-known fact” that whites will become increasingly rare because they are more common in the lower birth-rate developed world. I’d love to see a full analysis of how this would play out though versus this possible human bias for lighter skin.
Finally, my own theory: short term there will be a continuing increase in the proportion of coffee-coloured people, and probably a decrease in the proportion of skin colours at the two extremes. Long term, I suspect genetic engineering of skin colour will become socially acceptable, and all bets are off.
I will point out that if people, as a whole, value one coloration over another, that in itself will lead to a difference in mating frequency. All those white guys will suddenly have more partners available (assuming they’re interested), and all the dark guys will be left out.
Okay, maybe not that dramatically, but the point is that the choice of what is attractive will drive where the blend ends up.
In fairness to Irishman, he was just leading on from Cecil’s assertion, the same as I did.
I agree with you that it’s not at all obvious that there is a worldwide preference for lighter skin.
And also the image of white people getting all the action even now seems absurd, let alone if supposedly black skin becomes increasingly rare (and therefore novel).
I guess all this answers my OP. Cecil’s answer to the question was a little simplistic, but it’s as good as any analysis is likely to be, because the real social dynamics are complex and fluid. We can’t really project into the future by the kind of timespans required.
As anyone who has read “Ringworld” by Larry Niven, once we get transfer booths, we will shortly all look sort of Asian. Although I think that the A380 will probably suffice.
And I think it will be a shame when it happens in about the next hundred years. The variety of humanity is a wonder. When everyone looks alike, we will have lost something.
Of course, populations can migrate and intermarry much faster now than they could for the majority of human history, but those descendants of mixed parentage will probably adapt to their exposure to UV light. In several centuries Lithuanians may be somewhat darker and Eritreans somewhat lighter than today, and the tendency to stay indoors much more than our ancestors will probably lighten much of the earth’s population also. But I doubt that our descendents will ever all be the same color.
In his excellent The Forever War, set partly a few thousand years hence, Joe Haldeman suggests that we’ll all look vaguely like Pacific Islanders by then due to interbreeding among humanity’s various distinct racial groups.
Well, that’s the usual assumption, but it seems that the facts are different.
It is true, though, that many non-white cultures prefer light skin. There is also a strong preference for blonde women, at least among white men. I am personally an exception to that rule, perhaps because I was annoyed by Clairol commercials as a tween/teen, but there is both historic and genetic evidence for it.
(Interestingly, though, the cultural expression of the preference for blondes has varied. In novels written before divorce was readily accepted, blondes are faithful fiancées and wives, while brunettes are temptresses, or, at best, tragic figures like Rebecca of York; now it’s the other way around.)