Mommy’s Little Secret

From the Globe and Mail:

As we gather to mark the festive season, here’s one juicy morsel mom won’t be dishing up: that guy you call your dad may not be. DNA testing has revolutionized medical science, CAROLYN ABRAHAM reports, but it also has uncovered the myth of female monogamy. Now doctors are wondering how to break the news to men

By CAROLYN ABRAHAM, Saturday, December 14, 2002 – Print Edition, Page F1

They came to the hospital together, a husband, a wife and the little daughter they feared had been cursed by inheritance. Since birth, she had struggled to breathe, and all the signs pointed to cystic fibrosis.

If the girl truly had the incurable disease that clogs the lungs, she had to have received two copies of a CF gene, one from each parent. Tests at the Hospital for Sick Children in Toronto confirmed the family’s worst fears — and then some.

The girl was indeed afflicted. Her mom carried one of the culprit genes. But her dad, the doctors discovered, was quite a different story. His DNA showed no sign of a CF gene, which means he is not a carrier and he is not her dad.

Hospital staff have felt bound to keep the secret from him. But when they told the mom, it came as no surprise; it rarely does.

"It is probably true in a lot of families, that daddy is not who you think it is," says Steve Scherer, a senior scientist in department of genetics at the Hospital for Sick Children.

As families gather this festive season, here is a spicy fact that mothers might be loath to dish out at the holiday table: It’s now widely accepted among those who work in genetics that roughly 10 per cent of us are not fathered by the man we believe to be dad.

Geneticists have stumbled upon this phenomenon in the course of conducting large population studies and hunting for genes that cause diseases such as cystic fibrosis. They find full siblings to be half-siblings, fathers who are genetic strangers to more than one of their children and uncles who are much closer to their nieces and nephews than anyone might guess. Lumped under the heading of "pedigree errors," these so-called mis-paternities, false paternities and non-paternities are all science jargon for the unwitting number of us who are chips off someone else’s block.

The proverbial postman seems to be ringing twice in everyone’s neighbourhood. Non-paternity is believed to cut across all socio-economic classes and many cultures. Factor it into genealogical attempts to trace ancestry and it can snap entire branches from a family tree. Considered in light of long-held views about sexual behaviour, it exposes the myth of female monogamy and utterly shakes the assumption that women are biologically driven to single-mate bliss.