In the United States, men confident about their paternity are almost always right, but those who insist that children are not their own are correct only 30 percent of the time, a new study finds.
A review of more than 65 studies of paternity has concluded that actual rates of nonpaternity — cases in which a man incorrectly believes he is biologically related to a child — are much lower than the widely cited 10 percent.
"Many of our beliefs about nonpaternity are based on anecdotes or hearsay," said Kermyt G. Anderson, the lead author of the study and a professor of anthropology at the University of Oklahoma. "We don't know exactly how many men think they're the father and how many don't. But the 10 percent figure is almost certainly inflated."
Using the most extensive data on nonpaternity rates assembled to date, the researchers tentatively concluded that men confident about their paternity are usually right: they are biologically unrelated only 1.7 percent to 3.7 percent of the time.
Those who insist they are not the fathers, on the other hand, are in fact the biological fathers in more than 70 percent of cases, a figure derived from data released by paternity testing laboratories.
The researchers found that figures varied widely depending on the group examined, and they cited published studies that included a range of nonpaternity rates from four-tenths of 1 percent in Sephardic Kohanim, or Jewish priests; 3.7 percent in Britain; 9.1 percent among the Yanomamo of Brazil; and up to 11.8 percent in some parts of Mexico. The review will appear in June in Current Anthropology.
"There's a daytime talk show aspect to this that people are always interested in," Dr. Anderson said, but, he added, "This clearly has important implications for child well-being and family dynamics."