Ever heard the statistic that 10% of children are being raised by the wrong father? Allegedly, one in ten children was fathered through cuckoldry, and millions of men nationwide are helping to raise children who (biologically) aren't theirs. The existence of the "Who's Your Daddy?" DNA-testing truck and the recurrence of paternity disputes on drama-filled TV shows suggest that this is a worry for a significant number of men.
But the commonly cited statistic, the origin of which is unclear, has long since been proven erroneous. According to one analysis of dozens of relevant studies, the actual number is more like 2 to 4%, depending on the family's culture and socioeconomic level. Men who have reason to suspect that their children are not biologically theirs and who seek out DNA testing are, unsurprisingly, significantly less likely to be biological fathers. But even in this sample, about seven in ten men are the fathers of the children whose origin they doubted. So men with little reason to doubt their paternity can rest assured that the children they're raising are almost certainly theirs.
This fact matters on a societal level as well as a personal one, for men are more apt to be actively involved dads when they feel confident that children are biologically theirs. David Popenoe summarizes the relevant research in Families Without Fathers:
From an evolutionary viewpoint, if a man is to stay with one woman rather than pursue many, he will desire a very high degree of "paternity confidence," the belief that offspring are really his. There is no genetic advantage to him for investing in another man's child. For this reason, some evolutionists believe that monogamy arose first and that high paternal investments evolved only after monogamy had produced increased paternity confidence.
The paternity-confidence phenomenon has been clearly discerned in today's premodern societies. Anthropologists Steven Gaulin and Alice Schlegel carefully analyzed and compared the sexual norms and practices in 186 preindustrial societies for which adequate data are available, concluding that a male tends to invest in his mate's children only when his paternity confidence is high. . . . Other studies have shown that mating systems in which paternity is relatively unacknowledged and downplayed and paternal investments are minimal are those in which confidence of paternity is low.
That paternity confidence should in fact be high in the contemporary U.S. is good news not just for doubting fathers, then, but for the kids who benefit from dads' involvement in their lives.