Cousin Marriage And Horndogging

Everyone is descended from royalty, apparently.

This seems trivial when you think of it in terms of exponential powers of two. A thousand years ago, for example, each of us has this many direct living ancestors:

2^50

or

281474976710656

Obviously there weren’t that many people alive then, so there’s been a lot of cousin marriage in everyone’s families. these seems to surprise a lot of people.

Genealogical data is suspect because of its very subjective nature. People always want to find royals, and royals/upper classes are over-represented in historical records. But what’s written down on paper doesn’t always represent sweaty, dripping reality.

Sociology often uses the idea of genetic paternity to trace “human copulatory behaviour”. In anonymous testing, and differentiated according to culture, you regularly find that somewhere between 5-15% of individuals do not in fact share genetics with their assumed birth fathers. This is per generation. Extrapolate this over a few centuries and you find that horndogging humans have made a mockery of even the most carefully recorded genealogies.

Baker and Bellis are convinced that sperm competition “has been the main force to shape the genetic programme that drives human sexuality”. But their nationwide survey, they estimate that in the late 1980’s about 4% of children were conceived while their mother contained within her reproductive tract sperm from two or more men.

This is from the charmingly titled Human Sperm Competition: Copulation, Masturbation, and Infidelity. I also recommend Promiscuity : An Evolutionary History of Sperm Competition.