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"The argument goes that in the highest primates, 99% of DNA is the same as human DNA," says Lawrence Cunningham, a theologian at the University of Notre Dame. "But what's significant is that 1% difference. It is a kind of moral evolution that takes place within humans."
Surprisingly, many scientists agree. "There's a history in primatology of looking at primate species as if they were models for humans," says evolutionary psychologist Leda Cosmides of the University of California at Santa Barbara. "But that's not really the way to do it, because humans are not baboons or chimps, just as baboons are not chimps or humans."
Just what distinguishes the higher species of primates from the very highest one is not always clear, but one of the most important differences seems to be the delight humans take in challenging their primitive urges--and even flat-out defying them. Hrdy writes that when her children were babies, she often cooed to them nonsensical endearments that were oddly evocative of food. "Sweet potato," "muffin," "cutie-pie," she would call them. "I could eat you up," she'd gush. Why she chose those words to babble, she couldn't say, but after a period of what she calls "Darwinian self-analysis," she realized that she might actually be hearing the echo of some genetic programming buried deep within the carnivorous parts of her brain.
Hrdy, of course, never had any real inclination to consume her children with anything other than affection. In fact, she became consumed by them--by their needs, by their demands, by her own impulse to protect them. In human mothers--indeed, in all animal mothers--there has always been tension between much that is sublimely good and at least a few things that aren't so good. It is humans alone, however, who have the ability to contemplate those choices--and then know which ones to make.
--Reported by Dan Cray/Los Angeles, Unmesh Kher/New York and Maggie Sieger/Chicago