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her chimps at Gombe. | think I have seen it among the pack of dogs, led by my father’s favorite “Sean”, at Sutton Place. That would count as one of the practical constraints. Too little support for family over equally deserving others is seenasa fault, and too much as another. The reason is obvious. Jack’s ambitions for kin will eventually conflict with Zack’s, just as with ambitions for food and nest sites and mating opportunities. Not everyone's firstborn can be king of the hill. Social creatures evolve agonistic rules to settle such conflicts peacefully. Losers in mating tournaments, or in contests where males display and females choose, usually survive to compete again next year. The contest is in the group interest because the traits of strength and skill proved in the winner will be those passed on. Our genes tell us to compete as best we can for the sake of a fair test, and to stop when the verdict seems clear. And soon enough it does. The quarterback tries his best for three downs to move the yardsticks, but trots to the sidelines on fourth down for the sake of another chance later. If genes can encode this farsighted strategy for those other kinds of competition, why not for nepotistic competition too? For decades, biologists wondered why genes need so much selecting in species long established. Shouldn’t earlier contests have selected the fittest genes once and for all, with no need for further ones but to screen out recent and harmful mutations? Shouldn't the best traits have become clear millennia ago? Why need males contest in tournaments or beauty contests every breeding season, with mostly the same contestants, when best genes ought to have proved themselves soon after the species began? Then there would be no genetic diversity except for recent mutations not yet screened out. Population genetists such as Fisher, J. B.S. Haldane and Sewall Wright had written mathematical models showing that even the slightest selection pressures should drive a gene to fixity, and its rivals to extinction, within a few generations if selection favored it consistently. Their argument was Malthus’ insight: breeding success is geometric. Yet there is rich allelic diversity wherever we look. There are some gene sites in some species where the most common allele Chapter 7 Petty’s Idea 2/3/16 6 HOUSE_OVERSIGHT_011065