The Economist unpacks new research suggesting that humans are not born equally promiscuous:
As with many biological phenomena—height, for example—propensity for promiscuity in either sex might be expected to be normally distributed; that is, to follow what are known colloquially as “bell curves”. The peaks of these curves would have different values between the sexes, just as they do in the case of height. But the curves’ shapes would be similar.
Rafael Wlodarski of Oxford University wondered whether things are a little more complicated than that. Perhaps, he and his colleagues posit in a study just published in Biology Letters, rather than cads, dads and their female equivalents simply being at the extremes of a continuous distribution, individual people are specialised for these roles. If so, the curve for each sex would look less like the cross-section of a bell, and more like that of a Bactrian camel, with two humps instead of one.
They found some evidence to back that theory up:
These results suggest that—probably for men and possibly for women—caddishness, daddishness and so on are indeed discrete behavioural strategies, perhaps underpinned by genetic differences, rather than being extremes of a continuum in the way that tall and short people are. Although there is some overlap between the two strategies, they are, if Dr Wlodarski and his colleagues are correct, what biologists call phenotypes. These are outward manifestations of underlying genes that give natural selection something to get hold of and adapt down the generations.
Intriguingly, the difference in phenotypic mix between the sexes is not huge. Dr Wlodarski and his colleagues calculate that cads outnumber dads by a ratio of 57:43. Loose women, by contrast, are outnumbered by their more constant sisters, but by only 53:47. Each of these ratios tends in the direction of received wisdom. Both, though, are close enough to 50:50 for that fact to need an explanation.
So much more to find out about us as a species. And now, finally, some time …