PRIVATES FIRST CLASS

Baboons Obviously can't make verbal promises," Dartmouth anthropologist John Watanabe says with a straight face. Instead, he reports, they form alliances by "literally putting their reproductive success in the hands of rivals." Watanabe, along with U-Michigan primatologist Barbara Smuts, has observed that one of the few friendly interactions between male baboons consists of patting each other on the testicles.

Could our ancestors have greeted this way? Watanabe notes that Australian aborigines and Old Testament prophets have used a similar ritual.