For instance, a highland New Guinea tribe decided to raid a nearby tribe after convening a meeting of all former and current members of a society for adult males. Several leaders solicited the candid views of everyone present and withheld their own opinions early on. Dissenters then experienced considerable social pressure to take part in the raid, since the tribe's survival was at stake. This type of egalitarian decision making, practiced by nomadic groups that keep their leaders on a short leash, has predominated for at least the past 50,000 to 100,000 years, Boehm contends. These groups vigilantly monitor and control their leaders' access to big game meat and reproductive partners, he contends.
Collective decision making further restrains leaders' personal ambitions.
Moreover, differences in the ways groups deal with climate change, competition for food sources, and other threats can dramatically alter their reproductive fortunes. Thus, repeated confrontations with crisis decisions may have magnified the effects of group selection on Stone Age humans. Advocating group selection as a force in human evolution has become like violating the incest taboo. Determined researchers can find ways to attribute cooperation, morality, and other group-oriented traits to the myriad deceptions of ultimately selfish individuals, Wilson responds. It will take decades for a full consensus to emerge.