In a particularly stimulating study, researchers have found that lap dancers–women who work in strip joints and, for cash, gyrate in the laps of seated men–earn more when they are in the fertile phase of their menstrual cycle. The finding suggests that women subtly signal when they are most fertile, although just how they do it is not clear.
Women, unlike many mammals, don’t come into heat or estrus, a state of obvious fertility that attracts potential mates. Common wisdom has it that estrus was lost as humans evolved. The notion is that women evolved “concealed ovulation” along with around-the-month sexual receptivity the better to manipulate males by keeping them in the dark, says Geoffrey Miller, an evolutionary psychologist at the University of New Mexico in Albuquerque. But now Miller and colleagues have found evidence that a woman’s state of fertility may not be so secret after all.