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

466 J HOW THE MIND WORKSany other male, so his sperm do not have to compete. Gibbons, who aremonogamous, have small testicles, too.In almost all primates (indeed, in almost all mammals), the males aredeadbeat dads, contributing nothing to their offspring but DNA. Otherspecies are more fatherly. Most birds, many fishes and insects, andsocial carnivores such as wolves have males that protect or feed theiroffspring. The evolution of male parental investment is helped along byseveral things. One is external fertilization, found in most fishes, wherethe female drops her eggs and the male fertilizes them in the water. Themale is guaranteed that the fertilized eggs carry his genes, and sincethey have been released while the young are undeveloped, he has anopportunity to help. But in most mammals the cards are stacked againstdoting fatherhood. The egg is tucked away inside the mother, wheresome other male can fertilize it, so a male is never certain an offspring ishis. He faces the danger of wasting his investment on another male'sgenes. Also, the embryo does most of its growing inside the mother,where the father can't get at it to help directly. And a father can easilydesert and try to mate with another female, whereas the female is leftholding the bag and cannot get rid of the fetus or offspring without havingto go through the long process of nurturing an embryo all over againto get back to where she started. Fatherhood is also promoted when aspecies' lifestyle makes the benefits exceed the costs: when the offspringwould be vulnerable without him, when he can easily provisionthem with concentrated food like meat, and when the young are easy todefend.When males become devoted fathers, the rules of the mating gamechange. A female may choose a mate based on his ability and his willingnessto invest in their offspring, insofar as she can judge. Females, notjust males, compete for mates, though the prizes are different: malescompete for fertile females willing to copulate, females compete forflush males willing to invest. Polygamy is no longer a matter of one malebeating up all the others, or the females all wanting to be inseminated bythe fiercest or prettiest male. When males invest more than females, aswe have seen, the species may be polyandrous, with tough females keepingharems of males. (The mammals' body plan has foreclosed thatoption.) When one male has much more to invest than others (because,say, he controls a better territory), females may be better off sharinghim—polygyny—than each having her own mate, because a fraction of abig resource may be better than the entirety of a small one. When males'