SuperFreakonomics

The authorities who oversaw the monkey lab feared that introducing money to the capuchins would irreparably damage their social structure.

They were probably right.

If the capuchins were so quick to turn to prostitution as soon as they got hold of some money, just imagine how quickly the world would be overrun with monkey murderers and monkey terrorists, with monkey polluters who contribute to global warming and monkey doctors who fail to wash their hands. Future generations of monkeys, of course, would come along and

solve these problems. But there would always be something to fix—like the monkeys’ pigheaded insistence that all their children ride in car seats

What Chen had seen wasn’t altruism at all, but rather the first instance of monkey prostitution in the recorded history of science

Chen saw something remarkable. One monkey, rather than handing his coin over to the humans for a grape or a slice of apple, instead approached a second monkey and gave it to her. Chen had done earlier research in which monkeys were found to be altruistic. Had he just witnessed an unprompted act of monkey altruism?

After a few seconds of grooming— bam! —the two capuchins were having sex