Evolution and birth

Interesting connection between fat and newborns. I am on vacation catching up on my significant stack of unread New Yorkers and in the July 20th issue Elizabeth Kolbert has an interesting piece on the many books out there postulating on why we as a society are fat. In it, she discusses "The Evolution of Obesity" (Johns Hopkins), written by researchers at the American College of Obstetricians and Gynecologists. The authors argue that a person with a genetic knack for storing fat would have a competitive advantage in life because fat is energy rich and lightweight (surprisingly) and it helps our big brains run. "Human infants," Kolbert writes, "are unusually portly; among mammals, only hooded seals have a higher percentage of body fat at birth....Tellingly, humans, unlike most other animals, have no set season of fertility. Instead, ovulation is tied to a woman's fat stores: Those who are very thin simply fail to menstruate."