Human behaviors are often explained as hard-wired evolutionary leftovers of life on the savannah or during the Stone Age. But a study of one very modern behavior, fairness toward total strangers one will never meet again, suggests it evolved recently, and is rooted in culture rather than biology. In a series of behavioral tests given to 2,100 people in societies around the world (from hunter-gatherers to wage laborers), an innate sense of fairness dovetailed with participation in markets and major religions. "You can't get the effects we're seeing from genes," notes evolutionary psychologist Joe Henrich. "These are things you learn as a consequence of growing up in a particular place."
