A key organ of romance?
Women subconsciously prefer the aroma of dominant men when they are at the most fertile stage of the menstrual cycle, research suggests.
Researchers in Prague asked 48 men to assess how dominant they felt.
The men then wore cotton pads in their armpits for 24 hours, which were
subsequently presented to 65 women.
Those who were ovulating rated the "dominant" men as sexiest, but there was no similar pattern among women at other stages of their menstrual cycle.
The findings, published in Biology Letters, suggest women are evolved to seek out the most virile sexual partner when conception is likely.
But the rest of the time they probably prefer potential social partners.
Each of the women taking part in the experiment rated the odour of 10 pads for their intensity, sexiness and masculinity.
The researchers found women who were ovulating were more likely to rate the odour of dominant men as sexy.
This was particularly the case among women who were in a relationship.
However, women at other stages of their menstrual cycle - single or not - did not pick out dominant men in the same way.
Researcher Dr Craig Roberts told the BBC News website: "There seems to be some sort of physiological mechanism that directs women to indicators of good genes.
"The offspring of such a coupling would therefore be likely to have better genes."
Previous research has shown that emotional state may influence perception of body odour quality.
However, the researchers admit that the exact mechanisms in play are not known.
Dr Nick Neave, of Northumbria University, said human scents, or pheromones, played a complex role in how people interacted with each other.
His work has shown that women were more likely to rate male pheromones as coming from a dominant or assertive individual.