Midnight Sex Talk this week was a feast of information. A big thank you to clinical geneticist Dr Adam Shaw for explaining so much so clearly.

We started off by talking about The Cement Garden by Ian McEwan (1978), which I think, for a lot of people, was a seminal early introduction to incest; in literature and elsewhere. I well remember the smells from that book, and the giggles at school.

You’ll here the word consanguinity a lot. A consanguineous marriage is between any blood-related people, but not necessarily closely; it’s more accepted in some cultures than others. It improves the odds of genetic diseases in children, and the more closely related you are, the worse it gets. The basic medical conclusion is, if you’re going to have an incestuous affair, for god’s sake don’t have children.

The flipside of Genetic Sexual Attraction is called the Westermarck effect. Have a look at the studies of kibbutz children and Chinese arranged marriages, where tiny girls were sent off to the future boy-husband’s family for pre-marital conditioning. The studies tell us that familiarity breeds contempt, and after growing up together as children, most people would rather go and live in a poorly-heated shed at the South Pole than get it together as man and wife.

We also played a clip from Chinatown. If you haven’t seen it, go and get it now.

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