The team interviewed 66 heterosexual couples in which women’s ages ranged from 18 to 44. Their relationships ranged from one month to 20 years in length. Nine couples were married.

A host of studies has shown that women’s interest in men with masculine features peaks during ovulation. But this study is the first to confirm that the effect occurs in real couples.

“The effects of facial masculinity and attractiveness fit in a larger picture that has emerged,” says Garver-Apgar.

The prevailing wisdom during much of the last half-century was that women did not experience estrus, the period in which other primates signal their fertility with swollen genitals. But newer research suggests that women may not have lost all remnants of estrus.