WHAT'S a girl to do when faced with the choice between a powerful action man who has great DNA but is likely to love her and leave her, and a carpet-and-slippers kind of bloke who will hang around and bring up the kids but may not be Mr Right in the genes department? Well, ideally, she should fool the latter into bringing up the former's children. And a piece of evidence that this is exactly what happens emerged this week from a research group led by Jan Havlicek of Charles University, in Prague.

Dr Havlicek and his colleagues were interested in discovering whether women are attracted by the smell of dominant men. A preference for the scent of dominants has been found in the females of other species, and scent is known to be important in attraction between the human sexes in other contexts, such as avoiding inbreeding. The attractiveness of body odour is also correlated with the attractiveness of the body it came from, even when presented separately from that body. But whether the odour of power—or, at least, of powerfulness—is attractive to women had not been established.

Deciding who is and is not a dominant male is the first question, of course. To do this, the researchers turned to one of the world's most widely used experimental animals, the hard-up male student. Their subjects were asked to rate such things as their tendency to correct others, to want to control conversations, and to surpass others' accomplishments, in a questionnaire designed to assess their dominance. In their paper in Biology Letters the researchers laconically observe that dominance in this questionnaire “corresponds to the scale ‘Narcissism' in the widely used California psychological inventory”.

After baring their all in this manner, the volunteers had to wear cotton pads under their armpits for 24 hours to collect the sweat therefrom, and also had to lay off curries, beer, cigarettes and similar delights of student life that might affect the smell of their sweat. Surprisingly, given these constraints, the researchers managed to persuade 48 men to volunteer.

Compared with this, the female volunteers had it easy. They had to smell the pads and rate them for “intensity”, “sexiness” and “masculinity”. Okay, perhaps not that easy. They also had to vouchsafe whether they were single or in an on-going relationship with a man, and to submit to a saliva test that would show the phase of their menstrual cycle.

The upshot of the trial was that women did, indeed, find the odour of dominants sexier than that of wimps—but only in special circumstances. These circumstances were first that the woman was already in a relationship and second that she was in the most fertile phase of her cycle. In other words, dominant males' scent was only more attractive at the point where a woman could both conceive and cuckold her mate. Which, given previous studies that show dominant men are indeed more likely than others to leave a woman holding the baby, makes perfect sense.