Well - unrealistic but affecting only the numerical details and not the logic of the argument If there is not enough food or some other limiting

Well, population growth is function of individual reproduction; so this really means individuals would have to evolve mechanisms to produce fewer offspring than they could currently support so that in the long run resources weren't overexploited Suppose we start with a population composed of such reproductively-restrained types, comfortably below the long-term sustainable population size (Starting here of course begs the question of how the population evolved to be composed of restrained types; but since such a starting point is adaptive for the population, it makes the subsequent story even more convincing in exposing the weakness of simple group-benefit arguments) Then allow a mutant to arise that raises 3 offspring instead of just the replacement number of 2 (note: 2 offspring = "replacement" if each offspring has 2 parents, as in any sexually- reproducing species, and if there is no mortality before reproduction -- the last assumption being

This is the end of the preview. Sign up to access the rest of the document.

Unformatted text preview: unrealistic, but affecting only the numerical details and not the logic of the argument) If there is not enough food or some other limiting resource to successfully raise all 3 offspring, then natural selection will not favor the higher (mutant) reproductive rate; but if 3 offspring can be successfully raised, and this mutant prolific strategy is heritable (think of some behaviorally stereotyped organism like an insect, not humans!), then it will begin to increase in the population Similarly, the prolific strategy can spread by gene flow from adjacent populations Even though in long run the prolific strategy may doom the population to overexploit its resource base and crash, it is still favored by individual-level selection; and this will overwhelm group-level selection in all but exceptional circumstances (involving frequent group extinction, extremely low rates of gene flow between groups, etc.)...
View Full Document