Marlene Zuk on the truth about misassigned paternity

"Father's Day inspires sentimental cards, tacky neckties, cheap aftershave and, at least in some circles, suspicion and doubt. What if the child you think is the fruit of your loins actually sprang from someone else's seed?

With DNA tests now widely available, so-called paternity fraud has become a staple of talk shows and TV crime series. Aggrieved men accuse tearful wives who profess their fidelity, only to have their extramarital affairs brought to light. Billboards in Chicago and other cities provocatively ask, "Paternity questions?" and advise that the answers are for sale at your local pharmacy in the form of at-home DNA paternity tests. Some fathers'-rights groups in Australia have called for mandatory paternity testing of all children at birth, with or without the mother's consent or even her knowledge.

And people are pretty well convinced there is a need for all this vigilance. When asked to estimate the frequency of misassigned paternity in the general population, most people hazard a guess of 10%, 20% or even 30%, with the last number coming from a class of biology undergraduates in a South Carolina university that I polled last year. I pointed out that this would mean that nearly 20 people in the class of 60-some students had lived their lives calling the wrong man Dad, at least biologically. They just nodded cynically, undaunted. Even scientists will quickly respond with the 10% figure, as a geneticist colleague of mine who studies the male sex chromosome found when he queried fellow biologists at conferences.  ..."