If you thought that humans as a species were finished evolving, Yale University researchers have proven you wrong. The New Scientist reports that tomorrow's women "are likely to be shorter and plumper, have healthier hearts and longer reproductive windows." In an age where medical interventions can prolong life and help just about anyone deliver a baby, many people assumed humans were beyond natural selection. Evolutionary biologist Stephen Stearns says this isn't entirely true, pointing not to natural selection but to reproductive choices as the driving force behind our changing statures.
Stearns and his team used data from the Framingham (Mass.) Heart Study which tracked data from over 14,000 people spanning several generations. They charted over 2,200 post-menopausal women to take note if height, weight, blood pressure, cholesterol, and other traits correlated with their rate of childbirth. They found that the shorter, heavier women bore more children on average. According to the New Scientist, "Women with lower blood pressure and lower cholesterol levels likewise reared more children and -- not surprisingly -- so did women who had their first child at a younger age or who entered menopause later." Stearns noticed that these traits were passed on to the women's daughters and again to their daughters.
Should this pattern continue for the next 10 generations, researchers estimate the woman of 2049 to be two centimeters shorter and one kilogram heavier than her current female counterpart. In addition, these future women will bear children earlier and enter menopause later, leaving a longer fertility period. Stearns and his researchers feel that this trend indicates a genetic or evolutionary and not a cultural trend, though he does add that "analyses of other long-term medical data sets could shed more light on the interplay between genetics and culture."