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Are we still evolving....

Gene ExpressionBy Razib KhanMarch 2, 2011 12:23 AM


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The question whether humans are still evolving is something that crops up now and then. If the story is British you know that the evolutionary geneticist Steve Jones will be approached for his obligatory quote. There's apparently going to be a program today in Britain about continuing human evolution. You can already watch it online if you are British. In any case, there's at least going to be some balanced treatment if this BBC story is representative. Two quick points which I think need to be emphasized: - When we talk about natural selection there's too often a focus on nature. Exogenous shocks. A lot of intra-specific competition occurs between individuals, without nature intervening. Jacob Zuma has 20 children. Barack Obama has 2. If there are some differences in inherited trait values, then there's some selection going on right there. - Steve Jones likes to point out that death rates are low today compared to the historic average. But we're ignoring that ~2/3 of fertilized eggs are subject to spontaneous abortion. There's probably natural selection going on at this stage, and it may be that as more and more genetic load accumulates in human populations due to lack of death and, later conception and gestation, the miscarriage rate will increase concomitantly in a classic pattern of mutation-selection balance. A major difference between classical physics and biology is that because of evolutionary adaptive processes biology's parameters are protean. We may talk today about the end of natural selection, but the specter of infectious disease looms larger and larger with every coming year due to the rise of resistant bacteria. The Red Queen's race is still on.

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