Human estrus: implications for relationship science

• Primate females, and especially women, are unusually sexually active during non-fertile phases.
• But women's sexual interests are evoked by particular male features during the fertile phase.
• Two frameworks proposed to explain patterns are the graded sexuality and dual sexuality models.
• Women's attractiveness covaries with estradiol (positively) and progesterone (negatively).
• Multiple theoretical issues call for resolution.

Most mammalian females possess classic estrus, a discrete phase of the ovulatory cycle during which females engage in sex and undergo dramatic physical changes that make them attractive to males. By contrast, humans engage in sexual activity throughout the ovulatory cycle. But is it the case that humans possess no estrous-like changes across the cycle? Research over the past three decades has shown that, in fact, women's sexual desires change across the cycle, as do men's responses to women. Research over the last few years has sharpened scientific understanding of the precise nature of these changes. Nevertheless, many intriguing questions remain. We highlight recent work in this area and identify key opportunities for research in the future.