Evolutionary Theory Discussion on Gene Diversity and Selection Pressures

holds frequencies under ten percent, and those frequencies are constantly shifting. The flux proves that losers are allowed mating opportunities too, though not as much, and leave young to compete in the next generation. Hamilton explained why that could make sense in a paper published with Marlene Zuk in 1982. George Williams in 1976 and John Tooby in 1980 had argued that fittest genes in one generation might not be fittest in the next if niche pressures varied to counter current gene choices. Tooby had pointed to parasites and pathogens, particularly single-cell ones whose life cycle runs less than an hour. They could evolve new strains to outflank our old defenses and call for new ones. Hamilton and Zuk continued this theme. They suggested that genes might have long memories, put in human terms, and might have seen the same parasites and pathogens pull such tricks before. If some individuals in the host population still carried the antidote gene that worked the last time the same unexpected strain arose, or something close enough to it, hosts collectively could weather the threat if that antidote gene could be identified and spread fast enough. Then how? Hamilton and Zuk proposed that what winning males display in contests of singing or croaking or agility or symmetry, or bright colors in the right places, was possession of the genes needed to counter the current strains of pathogens and parasites. Losers in the same contests carried genes that had proved best against strains of the past and might come back in the future. Nepotism practiced by winners would speed up the spread of the current antidote. But losers carried genes that had worked against other strains that might recur. A way had to be found to keep all those potential antidotes somewhere in the medicine cabinet. Current losers had to be saved for later. Gene diversity was the key to group survival in the long run. The quarterback trots to the bench on fourth down because that is better for himself and the team than being carried to the hospital. He realizes that other players are best for punts or field goals or defense until he gets the ball again. Selection pressures do not favor the same traits and genes every time. Chapter 7 Petty’s Idea 2/3/16 7 HOUSE_OVERSIGHT_011066