From The Scientist:
...Ever since Charles Darwin, a prevailing attitude among medical practitioners has been that evolution does not operate in humans because modern medicine and culture have greatly leveled the playing field by homogenizing survival rates...
Not so, says Yale University's Stephen Stearns, who specializes in life history evolution. Survival rates have indeed evened out, particularly among children, yet human birth rates remain highly variable. Some people simply have more children than others. And if there's variation in lifetime reproductive success, and if some heritable trait is associated with that variation, then natural selection must be acting. To demonstrate natural selection in humans, however, requires a multitude of data collected over successive generations. Enter Framingham.
....
Early results show that women with lower cholesterol, lower blood pressure, lower blood glucose, and women who conceive earlier in life and reached menopause at a later age, all had more offspring. As a result, a model based on the data (that also controlled for social factors that influence fertility) predicts that levels of all these genetically based traits will change over the next generation. "People, myself included, may have written off evolution in humans," says Ewbank. "But it's still there. It's still happening." But the same response won't continue indefinitely. Obviously, says Stearns, "if selection continued to reduce cholesterol, we couldn't build a brain."
The researchers also plan to study several other traits of medical interest, including high-density lipoproteins, triglycerides, and bilirubin levels. The researchers have not yet looked at the genetics behind the trend, but neither did Darwin when he was studying natural selection, which can be demonstrated solely by showing statistically that a trait can be heritable and lead to larger family sizes. ...
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