By 2409 women should be a lot squatter than they are now

Josh Clark

Thanks a bunch to Mr. Rob Sheppe for sending along a link to a recent article in New Scientist about a prediction that in the future women will be shorter, plumper and have better tickers than they do now. The prediction was made by a Yale evolutionary biologist named Stephen Stearns, who looked at medical histories from what is arguably the most intensive and sweeping study every carried out in the history of the whole wide world, the Framingham Heart Study.

Back in 1948, a very clever person named Dr. Thomas Dawber thought it might be a good idea to begin a study that followed the residents of a single town in Massachusetts called Framingham. The extensive longitudinal study has been ongoing since then and it's yielded a wealth of information about things like cardiovascular disease, smoking habits, dementia, hearing disorders and, now, a snapshot of evolution at work.

As the New Scientist article points out, there's an established camp in the scientific community that believes we humans have effectively removed ourselves from the grip of natural selection thanks to medical interventions. It makes sense; back in the days of yore if you died young from a genetically-dictated disease, your genes were taken out of the natural selection race since you hadn't had time to reproduce. After this happens to enough people who shared that same genetic defect, say so long to the gene that killed you. With advances in the field of medicine, however, we can prolong the lives of people who would have otherwise died before passing along their mutation. Natural selection no longer has a chance to play its biggest card: death before reproduction.

The Yale researcher makes the point that this same type of advance hasn't been sufficiently applied enough to natural selection's other card, reproduction itself, to remove the evolutionary mechanism completely from our species. So he pored over the medical histories of 2238 women in the Framingham study who'd completed their reproductive years and entered menopause to see if there were any commonalities among them. He found that women who are shorter, plumper, have lower blood pressure and cholesterol levels and entered menopause later in life had more kids than their leaner, taller, less heart-healthy counterparts.

What makes this snapshot evidence of natural selection is that the women in the survey had daughters who shared the same traits and had more kids themselves. Anyone who's seen "Idiocracy" can do the math.

I've seen other suggestions that evolution may be influencing the life span of another group of women, this one members of the tribe of Ashkenazi Jews. Women in the group often live into their 100s (in far larger frequency than the population at large), and in 2008, an American researcher studying the population concluded that a mutation of the gene that controls production of insulin growth-like factor (IGF-1) is responsible for the longevity among the women in the group. But why not the men, too? If they all hail from one of the more racially isolated groups of humans in the world, shouldn't Ashkenazi men live long lives too? Here's where it gets interesting (finally). The researcher reasoned that the mutation was selective among women because greater longevity can lead to a longer reproductive age, which leads to more children and, hence, a greater chance of advancing the species.

Which puts any short, portly, highly fertile Ashkenazi woman with a good heart at the cutting edge of human evolution.

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More on HowStuffWorks.com: How can the world's oldest people also lead unhealthy lives? How Evolution Works How Natural Selection Works