Behavioral economists have revolutionized the standard view of human nature. No longer are people presumed to be purely selfish, only acting in their own interest. Hundreds of experiments appear to show that most people are pro-social, preferring to sacrifice their own success in order to benefit others. That's altruism. If the interpretations of these experiments are true, then we have to rip up the textbooks for both economics and evolutionary biology! Economic and evolutionary models assume that individuals only act unselfishly when they stand to benefit some way. Yet humans appear to be unique in the animal kingdom as experiments suggest they willingly sacrifice their own success on behalf of strangers they will never meet. These results have led researchers to look for the evolutionary precursors of such exceptional altruism by also running these kinds of experiments with non-human primates. But are these altruism experiments really evidence of humans being special? Our new study says probably not.