Male perception of cycle-related fluctuations in women's attractiveness

First paragraph: Women lack the conspicuous morphological and behavioral changes related to their menstrual cycle that are seen during estrus in some old-world monkeys, such as baboons, or in some apes, such as chimpanzees. In these species, changes in morphology and behavior — including genital swelling and active sexual solicitation — tend to peak in the fertile phase of the cycle and elicit elevated interest and sexual activity in their male conspecifics. Although they are not as conspicuous, some cyclic fluctuations in physical appearance and behavior can nonetheless be observed in women