from the short-but-neither-brutish-nor-nasty dept.
Hugh Pickens writes "Yale University researchers believe that if evolutionary pressures of sexual selection and reproductive fitness continue for another 10 generations, the trends detected in their study may mean that the average woman in 2409 AD will be 2 cm shorter, 1 kg heavier, will bear her first child five months earlier, and enter menopause 10 months later. 'There is this idea that because medicine has been so good at reducing mortality rates, that means that natural selection is no longer operating in humans,' says Stephen Stearns of Yale University. 'That's just plain false.' Stearns and his team studied the medical histories of 14,000 residents of the Massachusetts town of Framingham, using medical data from a study going back to 1948 spanning three generations, and found that shorter, heavier women had more children than lighter, taller ones. Women with lower blood pressure and cholesterol were also more likely to have large families as were women who gave birth early or had a late menopause. More importantly, these traits are then passed on to their daughters, who also, on average, had more children. The study has not determined why these factors are linked to reproductive success, but it is likely that they indicate genetic, rather than environmental, effects. 'The evolution that's going on in the Framingham women is like average rates of evolution measured in other plants and animals,' says Stearns. 'These results place humans in the medium-to-slow end of the range of rates observed for other living things.'"
Time is nature's way of making sure that everything doesn't happen at once.
Space is nature's way of making sure that everything doesn't happen to you.