Odd connections that come up in research in sexual attitudes and behaviours often makes on wonder whether it is a conflation of correlation with causation, that classic pitfall of extremely statistical views of the world.

And so too for this one. The key finding, that the structure of the face predicts attitudes about casual sex, is intriguing, but there is a plausible mechanism of causation that makes the correlations found in the study published in Evolution and Human Behavior very interesting. The plausible mechanism is of course the role that testosterone plays in shaping our features and indeed our views about casual sex.

The technical term for being open to more casual sex is 'unrestricted sociosexuality', while less openness to such sex is 'restricted sociosexuality'.

Broadly, more testosterone predicts more masculine features, and more masculine features have been mapped to unrestricted sociosexuality in this study by Joseph C. Antar and Ian D. Stephen. To a lesser extent, more feminine, attractive faces predict restricted sociosexuality, in the study.

Musing about why it would be so, one goes back, of course, to several millennia ago, when it would help for women to be able to 'pick' a partner who would be more likely to stick around for various roles during pregnancy, instead of, well, going off to seek the next sexual engagement. While these imperatives are not as significant now, with women having more agency, a legal system that would step in, and other societal factors, out instincts often take time to catch up, and attraction is all about instinct.

We shall continue to follow this space, but here's an interesting quiz that helps you index how you are doing on the intimacy front with your partner, in a steady relationship. Takes three minutes, so totally worth a look.