This is Dr. Sarah Blaffer Hrdy's (stet) new work. She's my favorite evolutionary biologist. If you've read Mother Nature: A History of Mothers, Infants and Natural Selection, you know why.
About the new work, from today's NY Times Science section:
[ Our capacity to cooperate in groups, to empathize with others and to wonder what others are thinking and feeling — all these traits, Dr. Hrdy argues, probably arose in response to the selective pressures of being in a cooperatively breeding social group, and the need to trust and rely on others and be deemed trustworthy and reliable in turn. Babies became adorable and keen to make connections with every passing adult gaze. Mothers became willing to play pass the baby. Dr. Hrdy points out that mother chimpanzees and gorillas jealously hold on to their infants for the first six months or more of life. Other females may express real interest in the newborn, but the mother does not let go: you never know when one of those females will turn infanticidal, or be unwilling or unable to defend the young ape against an infanticidal male.
By contrast, human mothers in virtually every culture studied allow others to hold their babies from birth onward, to a greater or lesser extent depending on tradition. Among the !Kung foragers of the Kalahari, babies are held by a father, grandmother, older sibling or some other allomother maybe 25 percent of the time. Among the Efe foragers of Central Africa, babies spend 60 percent of their daylight hours being toted around by somebody other than their mother. In 87 percent of foraging societies, mothers sometimes suckle each other’s children, another remarkable display of social trust.
Dr. Hrdy wrote her book in part to counter what she sees as the reigning dogma among evolutionary scholars that humans evolved their extreme sociality and cooperative behavior to better compete with other humans. “I’m not comfortable accepting this idea that the origins of hypersociality can be found in warfare, or that in-group amity arose in the interest of out-group enmity,” she said in a telephone interview. Sure, humans have been notably violent and militaristic for the last 12,000 or so years, she said, when hunter-gatherers started settling down and defending territories, and populations started getting seriously dense. But before then? There weren’t enough people around to wage wars. By the latest estimates, the average population size during the hundreds of thousands of years of human evolution that preceded the Neolithic Age may have been around 2,000 breeding adults. “What would humans have been fighting over?” Dr. Hrdy said. “They were too busy trying to keep themselves and their children alive.” ]
Full article here.