One prominent scientist calls another "a man whose ideas are so confusedas to be hardly worth bothering about." That eminent figure retorts that the first is guilty of "apocalyptic ultra-Darwinian fervor." In the halls of academe, such exchanges are equivalent to neighbors swapping obscenities over the back fence. Rancorous arguments about evolution are common, and evolution's role in human behavior is a favorite topic of debate. Richard Morris, a science writer with a doctorate in physics, brilliantly explains why such disputes are an integral part of good science.