Ideas about sexual selection have come a long way since Darwin, says Judy Stamps, UC Davis professor of biology, but you might not know it. More than 100 years ago, Darwin proposed two evolutionary explanations for conspicuous differences between males and females of the same species, such as peacock tails or deer antlers. He suggested that some of these traits help males win fights with other males, while others evolved because they are preferred by females. Until a few years ago, explanations based on male combat eclipsed those based on female aesthetics. "This lopsided view of sexual selection is still reflected in introductory biology textbooks, wildlife programs on TV and popular articles on the 'biology' of sex differences between males and females," Stamps says. In a recent meeting of the American Association for the Advancement of Science, she noted that female preferences for attractive male traits have now been documented in many animals. For example, when researchers clipped as few as 20 eye-spots from male peacock tails, female peacocks avoided the males. Other recent advances have led to new and unexpected hypotheses for gender differences in behavior and physical traits, she says, with an emphasis on behavior that is frequently more subtle to human observers than the male-male contests and on gender-neutral ideas about sexual selection that apply to females as well as males.