It's like the foxes that over-populate, eat all the rabbits and then all die. The foxes would be better not to reproduce past the limits of their environment, b

It's like the foxes that over-populate, eat all the rabbits and then all die. The foxes would be better not to reproduce past the limits of their environment, but each individual fox passes on more of it's genes if it doesn't restrain it's own breeding. And so those genes propagate to the detriment of the community. You need very strong group selection to restrain breeding, and this becomes less and less likely as the population size increases (so each individual has less and less affect.) See The Tradgedy of Group Selectionism: http://lesswrong.com/lw/kw/the_tragedy_of_group_selectionism/ http://lesswrong.com/lw/kw/the_tragedy_of_group_selectionism... Even when organisms are selectively breed by scientists with group selection to limit their population size, they often just become cannibalistic rather than restrain their own reproduction. Killing someone else's kids is better than killing your own. Essentially the same thing happens with viruses, where over reproduction means killing all the hosts cells.