Researchers from University of Gottingen in Germany found that women in the fertile phase of their menstrual cycle are judged as more attractive dancers by men than are women in a less-fertile phase.
The research suggested that ovulation is not as hidden in humans as scientists had once suspected.
"These changes are subtle, and women may not always be consciously aware of them. However, men seem to derive information on women's fertility status from these cues," Bernhard Fink, lead researcher told LiveScience.
The study asked 48 women aged 19 to 33 to dance to an identical drumbeat during both the late follicular, or fertile phase, of their cycles and the nonfertile mid-luteal phase.
Fertility was gauged by counting back from the woman's last period. Two hundred men, mostly undergraduate and graduate students, were then shown silhouettes of the women dancing. Hair was pulled back and the women wore identical form-fitting outfits to reduce the differences between them.
The results revealed that though the men had no idea fertility was even being studied, they judged fertile women as more attractive dancers than women in their nonfertile phase.
The researchers also captured video of the women's silhouettes walking and found that fertile women's gait was also judged more attractive than nonfertile women's.
Fink and his colleagues suspect that fluctuations in the hormone estrogen