New British research is rattling the roots of the family tree, citing paternity "discrepancy" in perhaps 4 percent of fathers studied.
"Paternal discrepancy" is a delicate term for a loaded subject. It refers to a man who wrongly thinks he's a child's biological father.
Paternal discrepancy was studied by researchers including Professor Mark Bellis, director of the Centre for Public Health at Liverpool John Moores University in England. Their findings appear in the Journal of Epidemiology and Community Health.
Bellis and colleagues checked studies from the 1950s through 2002 that mentioned paternal discrepancy. The studies came from the U.K., U.S., Europe, Russia, Canada, South Africa, South America, New Zealand, and Mexico.
Over the years, few studies directly tackled the topic. For instance, some researchers set out to screen for multiple sclerosis or cystic fibrosis, noting paternal discrepancies along the way.
Some studies were large; others included a handful of people. Paternal-discrepancy estimates varied wildly, from less than 1 percent to more than 30 percent.
But those numbers don't tell the whole story.
Some research centered on paternity disputes. Daddy discrepancies were probably overrepresented in those studies, writes Bellis.
Setting those studies aside, the remaining research showed an average paternal discrepancy of 3.7 percent, or a little less than one in 25 dads, write the researchers.
Don't Jump to Conclusions
That number doesn't necessarily mean that out of 25 dads at the ballpark, one isn't really his child's biological father.
Because the researchers extrapolated some information from studies involving topics other than paternity, they say that the percentage is not a true indication of paternal discrepancies in the general population. However, "it does suggest the widely used (but unsubstantiated) figure of 10 percent paternal discrepancy may be an overestimate for most populations," write the researchers.
In other words, paternal discrepancy might be rarer than commonly thought.
Rates were higher for disadvantaged people, for those with more than one sex partner at a time, and for younger women, write the researchers. "No clear population measures of paternal discrepancy are currently available," they note.
Infidelity? Maybe Not
Paternal discrepancy could stem from infidelity. But it can also happen if a woman changes partners and quickly gets pregnant. She and her partner might honestly (but mistakenly) think the baby was fathered by her current partner, not her ex.
Those issues are nothing new. But no matter how it happens, the "who's your daddy" question is being dragged into the spotlight by genetic screening -- with few resources for people caught in the glare, the researchers note.
'Pandora's Box' of Issues
"Modern genetic techniques continue to open a Pandora's box on hitherto hidden aspects of human sexual behavior," write the researchers.
Beyond the parents and child, there are often layers of other relatives on both sides of the family that could be affected by a sudden daddy disclosure. "Suspected infidelity is also a trigger for domestic violence against women," the researchers point out.
"In a society where services and life decisions are increasingly influenced by genetics, our approach to paternal discrepancy cannot be simply to ignore this difficult issue but must be informed by what best protects the health of those affected," state Bellis and colleagues.
SOURCES: Bellis, M. Journal of Epidemiology and Community Health, Sept. 2005; vol 59: pp 749-754. News release, BMJ.