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How many children are the mailman’s? Checking paternity.

Photo: Stefano Ricciardi. Creative Commons.

If you ever hear or read that about 10% of all assumed biological children are really the result of an infidelity, don’t believe it.

If you ever hear or read that about 10% of all assumed biological children are really the result of an infidelity, don’t believe it. Reliable studies of paternity in recent years show that this assertion is based on an urban myth, which seems to have originated at a medical convention in England in the 1950s. The myth has kept on being asserted in reports in the popular media and in the scientific literature as well.

DNA testing of paternity became popular at the turn of the century. Usually it is the supposed but disbelieving father who goes to paternity testing, but very often he is prodded by his new partner, obviously to avoid child support to the man’s ex-partner. When I checked the records of a German company offering paternity tests, I found that at the turn of this century three out of four men who had their paternity tested turned out to be the biological father after all! All or most of these men had doubts about their true paternity serious enough that they were willing to spend more than 1000 dollars for the test.

There are now scientific reports from several European countries (England, Switzerland, Germany) that show these days the actual prevalence of paternity discrepancy lies below 3%, most probably around a mere 1%, a figure that probably can be generalized to Western, educated, industrialized, rich, democratic (WEIRD) countries. A meta-analysis of all non-paternity reports revealed that since the 1960s, when the birth-control pill became widely available, the prevalence seems to have dropped from a higher rate to the current 1%.

Why are men’s fears of being cuckolded so high when such fears are mostly unfounded? The reason, I believe, lies in our history. We can roughly estimate what the prevalence of non-paternity was in earlier, ancestral times, by comparing the time and emotional closeness aunts and uncles invest in the offspring of their sisters compared to their brothers. The paternity uncertainty for nephews and nieces through a brother are higher than those through a sister because the sister but not the brother can be certain about biological relatedness to the child. From this asymmetry we estimate that in ancient times the prevalence of non-paternity was more than 10%. This probability is high enough to have made men wary about being cuckolded. If they were dumb enough to get cuckolded they would have invested their paternal effort into the progeny of another man (and they would not belong to our male ancestors). This may be one reason why men have wanted to guard their wives by various means and have often taken oppressive measures, believing that it is better to jump up because of burned toast than to have the house burn down. In this age of increasingly widespread birth control, the fear of raising another man’s child is increasingly becoming misplaced.

Harald A. Euler

Harald A. Euler

Professorial Research Fellow for Evolutionary Developmental Psychology, Dept. of Developmental Psychology, University of Vienna, Austria

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