Really not utter nonsense, though. Although 'extinct' is a headline term, because 'statistically negligible' doesn't sell papers, the basic idea is true. As we function more and more as a planet, and less and less as isolated groups, all phenotypical extremes, especially the recessives (and particularly recessives that already are only carried by a very small proportion of the planet) are going to become radically less common, especially in terms of the constellations of traits that we tend to identify as the notable physical traits of particular ethnic groups (although obviously traits that are carried close together on the same chromosome will take longer to dissociate from each other). Whether the original cause was simple genetic drift or evolutionary pressures of a particular environment, either way those we're going to see radically fewer of the extremes. Of course we'll always see variation, but it's not going to be at all in the way that we currently think about ethnicity, and people with vivid red hair (recessive trait), or deep black skin (which requires inheriting alleles for dark skin on all or almost all of the requisite genes), or body morphology extremes such as the Masai or Inuit, will become very, very rare.
To use an artificially induced example, any "purebreed" dog has a specific constellation of traits that we identify as that breed. Mixed-breeds have a much more random assortment of those traits, and they tend much less toward the extremes. I think this is generally a good thing, given all the health problems that often accompany those extremes, either as a direct result of the extreme itself (stomach torsion in large breeds, for example), or as an unfortune side-effect of in-breeding. However, it doesn't change the fact that two thoroughly Heinz 57 mixed-breeds don't produce chihuahas or Great Danes.
I love the current phenotypic variety among humans on our planet on a purely aesthetic level, but it's impossible not to be aware that the variety itself is fundamentally a result of isolation that is becoming less and less common.
As for mutations, yes, of course. However, the way mutations successfully spread is either through evolutionary pressure, or through genetic drift. In either case, small population size makes it a lot more likely, and a lot faster.
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Date: 2007-08-31 11:02 pm (UTC)To use an artificially induced example, any "purebreed" dog has a specific constellation of traits that we identify as that breed. Mixed-breeds have a much more random assortment of those traits, and they tend much less toward the extremes. I think this is generally a good thing, given all the health problems that often accompany those extremes, either as a direct result of the extreme itself (stomach torsion in large breeds, for example), or as an unfortune side-effect of in-breeding. However, it doesn't change the fact that two thoroughly Heinz 57 mixed-breeds don't produce chihuahas or Great Danes.
I love the current phenotypic variety among humans on our planet on a purely aesthetic level, but it's impossible not to be aware that the variety itself is fundamentally a result of isolation that is becoming less and less common.
As for mutations, yes, of course. However, the way mutations successfully spread is either through evolutionary pressure, or through genetic drift. In either case, small population size makes it a lot more likely, and a lot faster.
*off to read the snopes article now*