Steven Pinker -- How the Mind Works - Hampshire High Italian ...

Family Values 443children. The mother is a conservationist, trying to keep her body inreserve for posterity. The human placenta is a tissue of the fetus thatinvades the mother's body and taps into her bloodstream. Through it thefetus secretes a hormone that ties up maternal insulin, increasing thelevels of blood sugar which it can then skim off. But the resulting diabetescompromises the mother's health, and over evolutionary time shehas fought back by secreting more insulin, which prompted the fetus tosecrete more of the hormone that ties up insulin, and so on, until thehormones reached a thousand times their usual concentration. The biologistDavid Haig, who first noticed prenatal parent-offspring conflict,remarks that the raised hormone levels are like raised voices: a sign ofconflict. In a similar tug-of-war, the fetus increases the mother's bloodpressure, forcing more nutrients its way at the expense of her health.The battle continues once the baby is born. The first decision ofmotherhood is whether to let the newborn die. Infanticide has beenpracticed in all the world's cultures. In ours, "killing babies" is a synonymfor depravity, one of the most shocking crimes imaginable. One mightthink it is a form of Darwinian suicide and proof that other cultures' valuesare incommensurable with ours. Daly and Wilson show that it is neither.Parents of all species face the choice of whether to continue to investin a newborn. Parental investment is a precious resource, and if a newbornis likely to die there is no point in throwing good money after bad byfledging or suckling it. The time and calories would be better spent onits littermates or clutchmates, in starting over with new offspring, or inwaiting until the circumstances are better. Thus most animals let theirruntish or sickly offspring die. Similar calculations enter into humaninfanticide. In foraging peoples, women have their first child in their lateteens, nurse them on demand for four infertile years, and see many diebefore adulthood. If a woman is lucky, she might raise two or three childrento maturity. (The large broods of our grandparents are historicalaberrations resulting from agriculture, which provided substitutes formother's milk.) To raise even a small number of children to adulthood, awoman has to make hard choices. Women in the world's cultures letinfants die in circumstances in which the odds of survival are low: whenthe infant is deformed, a twin, fatherless, or fathered by a man who isn'tthe woman's husband, and when the mother is young (and so has opportunitiesto try again), lacks social support, had the infant soon afteranother child, is overburdened with older offspring, or is otherwise in