Research published in the recent issue of Ethology has discovered that men are able to potentially use smell as a mechanism to establish when their current or prospective sexual partners are at their most fertile.

Females of a number of primate species display their fertile period by behavioural and/or morphological changes. The prevalent opinion was that there are no noticeable changes in humans across the cycle. Havl’k et al, however, have found that women’s axillary odour is assessed most attractive in the follicular phase i.e. in the time when conception is most likely.

One of the possible mechanisms for assessing menstrual cycle phase is by means of smell. Thus the researchers investigated possible changes in odour across the menstrual cycle in a sample of 12 women with regular menstrual cycle, not using hormonal contraception.

To collect their body odour, they wore armpit pads for 24 hours under controlled conditions (food restrictions, no deodorants etc). Body odour was collected repeatedly during the menstrual, follicular and luteal cycle phase. Fresh samples were assessed namely for attractiveness and intensity by 42 men.

Axillary odour from women in the follicular phase was rated as the most attractive and least intense. On the other hand, highest intensity and lowest attractiveness was found during the time of menstrual bleeding.

The results suggest that body odour can be used by men as a cue to the fertile period in current or prospective sexual partners. Therefore, the fertile period in humans should be considered non-advertised, rather than concealed.

http://www.blackwellpublishing.com/eth