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Sunday, May 22, 2005

Cuckoldry not that common after all?

Claims that covert non-paternity (the putative father not being the actual father of a child) is as high as 10% in human populations have been common in recent years. Some time ago, I noticed that there was a discrepancy between this claim and studies done on the inheritance of surnames, which seemed to imply a much lower rate of non-paternity. If 10% of births in the typical family in the past were not actually the children of the father, it is easy to see that, after several generations, the relationship between a surname and the y-chromosome (that is, the actual paternal line) will become rapidly more tenuous. If 10% of "sons" of fathers, taking their father's surname, are actually another man's (the result of adultery), after seven generations less than half the surnames will accurately reflect the true male line [0.9 x 0.9 x 0.9 x 0.9 x 0.9 x 0.9 x 0.9 = 0.48 = 48 percent]. And yet there are studies, such as the Sykes surname study (cited here), extending over many past generations (700 years), which imply much lower rates of non-paternity (1.3% per generation in the Sykes case).

This recent study by Kermyt G. Anderson of the Department of Anthropology, University of Oklahoma, seems to imply that the lower figures for non-paternity are more probable:

" The results suggest that men with high paternity confidence are generally correct in their paternity assessment; these men overwhelmingly tend to be the actual genetic fathers of their putative children, with a median nonpaternity rate of only 1.9%. If men with high and unknown levels of paternity confidence are combined, the median nonpaternity increases to only 3.9%. These figures are dramatically less than the “typical” nonpaternity rate of 10% or higher cited by many authors (e.g., Alfred 2002, Cervino and Hill 2000, MacIntyre and Sooman 1991, Stewart 1989), or the median worldwide nonpaternity of 9% reported by Baker and Bellis (1995). These results presented here suggest that men who think they are the fathers of their children actually are the fathers between 96.1 - 98.1% of the time. "

The Sykes surname study has always seemed like powerful supporting evidence for a low rate of human cuckoldry. I have discussed this with various evolutionary psychologists on the Internet, and some have suggested that morals and behaviour have changed rapidly in recent years. That is, they have suggested that, whereas the Sykes study reflects stricter past behaviour, modern cultures around the world are more "free and easy" and 10% non-paternity is likely in their case. However, this new study from the University of Oklahoma implies that modern cultures are not more "free and easy".

To my mind, surname studies like the Sykes study have all along been very hard to explain if one believes in high (10%, for example) rates of cuckoldry (non-paternity) among humans. It is increasingly likely that what the Sykes study implies is accurate: that ordinary Englishmen and Englishwomen were, on the whole, remarkably well-behaved over a remarkably long time: "When all is said and done, there is more said than done." Despite the occasional shenanigans that undoubtedly went on, and that gave us so many colourful English expressions (like "cuckoldry"), the general picture is of a remarkably high standard of behaviour in an ordinary English population.

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