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yesh omrim

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Think of it as evolution inaction

27 October 2009

Stephen Stearns, an evolutionary biologist at Yale, believes that human evolution is still happening because, after all, some couples have more children than others, thereby changing the frequency distribution of alleles in the gene pool. So he and his colleagues went over some statistics from the Framingham Heart Study (going back to 1948) and discovered a few heritable traits that were associated with higher fertility [PDF]. From this, they vaulted into the pages of Time magazine with this stunning extrapolation:

If these trends were to continue with no cultural changes in the town for the next 10 generations, by 2409 the average Framingham woman would be 2 cm (0.8 in) shorter, 1 kg (2.2 lb.) heavier, have a healthier heart, have her first child five months earlier and enter menopause 10 months later than a woman today, the study found.

Why yes. And if human cultures had remained static for the past four centuries, we would also expect that the average Framingham woman of 1609 was 2 cm taller than her 21st-century counterpart, 1 kg lighter,…

I looked at the actual paper (which as of this writing is not yet behind a paywall) to see if this was dumb science or just dumb science journalism, and as far as I can tell, the fault is in the science. For instance, the authors, in their conclusions, speculate that “we might have found larger effects of evolution on the levels of sex hormones and related traits had they been measured”… as if human beings have done nothing since 1948 to affect the levels of their own sex hormones.

The process of natural selection pushes a species toward a local maximum of fitness relative to its environment. (When you speak of an organism’s “fitness” in an evolutionary sense, you always have to speak of its fitness relative to some environment, just as if you talk about the dollar “declining” in value, that decline is always relative to some other commodity.) If the environment is changing more rapidly then the evolutionary effects that adapt an organism to it, then the evolutionary effect might as well be noise.

Do these guys have an insight too subtle for me to appreciate, or are they just thick?

via Hacker News