A new study of birds concludes that parents get more help when they are sexually faithful to each other and "leaves little doubt that promiscuity corrupts social life in birds." Michael Balter reports on research that set out to test a monogamy hypothesis in birds. He says the researchers found a strong negative correlation between promiscuity rates and cooperative breeding. But ecologist Kathryn Arnold says its really life history factors, such as low adult mortality rates, which in turn lead to greater levels of care for the offspring. Balter notes that cooperative breeding is relatively rare. Among the apes, only humans are cooperative breeders.