After reviewing dozens of studies that examined men who are unknowingly raising the children of another man as his own, the University of Oklahoma and a group of British researchers have both determined that the rate of such men among the population is much higher than I think anyone would expect. The Oklahoma team determined that the rate is about 3.85 percent. The British researchers determined it to be 3.7 percent. Either way, there are well over a million fathers in the United States who think their children are biologically related to them, when in fact the are the product of infidelity. So this isn't just about the gap-toothed freaks that are the staples of daytime television talk shows: this is a problem that reaches into all economic strata.

Patrick Connaro, a 42-year-old robotics engineer living in Colorado Springs, realized his son's real father was someone else when he saw another man---with his son's features---cherring for him at a little league game (the suspicion was confirmed by a paternity test). Morgan Wise of Big Spring, Texas learned similar news when his fourth child was diagnosed with cystic fibrosis (CF). As the father, he was presumed to be a carrier of the CF gene, and Wise had his own DNA tested to identify which of the genetic mutations of the disease the boy had inherited. The test showed Wise did not carry any trace of CF in his DNA, which meant he was not the child's father.

This is a really tragic situation, because when men learn the truth---either through suspicion or accident---everyone is hurt. The men in these situations do not lose the love they have for their children, but they do lose something, and none of it is the child's fault. Obviously, many of these men continue to love and cherish their non-biological children, but oftentimes not with psychological difficulties due to the sense of betrayal. There are very deep cultural and evolutionary reasons why men care deeply about whether a child is their own. "It's not reproductively beneficial to invest all your resources in a child who is not carrying on your genetic line," says study author Rebecca Burch, Ph.D. "Men throughout the history of the species who have invested all their time and energy in children who weren't theirs no longer have genes in the population."