Critics assert that many hypotheses put forward to explain the adaptive nature of human behavioural traits are "Just-so stories"; neat adaptive explanations for the evolution of given traits that do not rest on any evidence beyond their own internal logic. They allege that evolutionary psychology can predict many, or even all, behaviours for a given situation, including contradictory ones. Therefore many human behaviours will always fit some hypotheses. Noam Chomsky noted:
"You find that people cooperate, you say, ‘Yeah, that contributes to their genes' perpetuating.’ You find that they fight, you say, ‘Sure, that’s obvious, because it means that their genes perpetuate and not somebody else's. In fact, just about anything you find, you can make up some story for it."[2][3]
For example, kin selection predicts that humans will be altruistic toward relatives in proportion to their relatedness, while reciprocal altruism predicts that we will be altruistic toward people from whom we can expect altruism in the future (but not strangers). A story of any complexity can be constructed to fit any behaviour, but, critics assert, nothing distinguishes one story from another experimentally
