Tuesday, October 20, 2009

Echidne The Girl Detective

Found out something odd. A story at New Scientist, about possible evolution of humans today, goes like this:

Women of the future are likely to be slightly shorter and plumper, have healthier hearts and longer reproductive windows. These changes are predicted by the strongest proof to date that humans are still evolving.

Medical advances mean that many people who once would have died young now live to a ripe old age. This has led to a belief that natural selection no longer affects humans and, therefore, that we have stopped evolving.

"That's just plain false," says Stephen Stearns, an evolutionary biologist at Yale University. He says although differences in survival may no longer select "fitter" humans and their genes, differences in reproduction still can. The question is whether women who have more children have distinguishing traits which they pass on to their offspring.

To find out, Stearns and his colleagues turned to data from the Framingham Heart Study, which has tracked the medical histories of more than 14,000 residents of the town of Framingham, Massachusetts, since 1948 – spanning three generations in some families.
Pass it on

The team studied 2238 women who had passed menopause and so completed their reproductive lives. For this group, Stearns's team tested whether a woman's height, weight, blood pressure, cholesterol or other traits correlated with the number of children she had borne. They controlled for changes due to social and cultural factors to calculate how strongly natural selection is shaping these traits.

Quite a lot, it turns out. Shorter, heavier women tended to have more children, on average, than taller, lighter ones. 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. Strikingly, these traits were passed on to their daughters, who in turn also had more children.

Then have a look at the picture they are using next to the story to show the kind of slim and tall woman who is going to go extinct:

A bit biased, eh? Note the suit and the briefcase.