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

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464 J HOW THE MIND WORKS<strong>the</strong> female's contribution is <strong>the</strong> limiting step on how many offspring canbe produced: at most, one offspring for each egg she creates and nurtures.Two cascades of consequences flow from this difference.First, a single male can fertilize several females, which forces o<strong>the</strong>rmales to go mateless. That sets up a competition among males for accessto females. A male may beat up o<strong>the</strong>r males to prevent <strong>the</strong>m from gettingto a female, or compete for <strong>the</strong> resources necessary to mate, or court afemale to get her to choose him. Males <strong>the</strong>refore vary in reproductivesuccess. A winner can beget many offspring, a loser will beget none.Second, <strong>the</strong> reproductive success of males depends on how manyfemales <strong>the</strong>y mate with, but <strong>the</strong> reproductive success of females doesnot depend on how many males <strong>the</strong>y mate with. That makes femalesmore discriminating. Males woo females and mate with any femalethat lets <strong>the</strong>m. Females scrutinize males and mate only with <strong>the</strong> bestones: <strong>the</strong> ones with <strong>the</strong> best genes, <strong>the</strong> ones most willing and able tofeed and protect her offspring, or <strong>the</strong> ones that <strong>the</strong> o<strong>the</strong>r females tendto prefer.Male competition and female choice are ubiquitous in <strong>the</strong> animalkingdom. Darwin called attention to <strong>the</strong>se two spectacles, which hedubbed sexual selection, but was puzzled as to why it should be malesthat compete and females that choose ra<strong>the</strong>r than <strong>the</strong> o<strong>the</strong>r way around.The <strong>the</strong>ory of parental investment solves <strong>the</strong> puzzle. The greater-investingsex chooses, <strong>the</strong> lesser-investing sex competes. Relative investment,<strong>the</strong>n, is <strong>the</strong> cause of sex differences. Everything else—testosterone,estrogen, penises, vaginas, Y chromosomes, X chromosomes—is secondary.Males compete and females choose only because <strong>the</strong> slightly biggerinvestment in an egg that defines being female tends to get multipliedby <strong>the</strong> rest of <strong>the</strong> animal's reproductive habits. In a few species, <strong>the</strong>whole animal reverses <strong>the</strong> initial difference in investment between eggand sperm, and in those cases females should compete and males shouldchoose. Sure enough, <strong>the</strong>se exceptions prove <strong>the</strong> rule. In some fishes,<strong>the</strong> male broods <strong>the</strong> young in a pouch. In some birds, <strong>the</strong> male sits on<strong>the</strong> egg and feeds <strong>the</strong> young. In those species, <strong>the</strong> females are aggressiveand try to court <strong>the</strong> males, who select partners carefully.In a typical mammal, though, <strong>the</strong> female does almost all <strong>the</strong> investing.Mammals have opted for a body plan in which <strong>the</strong> female carries <strong>the</strong>fetus inside her, nourishes it with her blood, and nurses and protects itafter it is born until <strong>the</strong> offspring has grown big enough to fend for itself.The male contributes a few seconds of copulation and a sperm cell

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