Understanding olfactory fertility cues in humans: chemical analysis of women's vulvar odour and perceptual detection of these cues by men

By conveying cues of their current fertility, females can provide valuable reproductive information to conspecifics. Our closest relatives, non-human primates, employ diverse strategies, including olfactory cues from the anogenital region, to communicate information about female fertility. While their shared phylogeny with humans suggests that analogous olfactory cues may have been preserved in modern women, empirical evidence is lacking. In a comprehensive two-fold approach, we investigated fertility-related shifts in the chemical composition of women's vulvar volatiles as well as men's ability to perceive them. We collected vulvar odour from 28 naturally cycling women (students, academic staff members, and citizen of Göttingen) on up to ten days of their menstrual cycle, focusing on fertile days. For 146 vulvar samples (subsample of n = 16 women), we assessed whether their volatile profiles varied in relation to female fertility using gas chromatography–mass spectrometry. Simulating a first encounter, 139 men evaluated a total of 274 vulvar odour samples from 28 women, collected on different cycle days. We used hormonal analyses to confirm women's fertile days. We assessed variation in chemical composition and male odour ratings in relation to women's conception probability, temporal distance to ovulation, and ovarian hormone levels. We found no evidence for chemical changes allowing tracking of fertility across the cycle. However, in the immediate assessment (i.e., without tracking), no significant effects were found for any predictors except conception risk. Notably, the significance of the conception risk effect varied depending on the model specification. Further, men's attraction to vulvar odour was not significantly predicted by female fertility. Overall, our data suggests a relatively low retention of chemical fertility cues in vulvar odour of modern women.