I'm not your father, Luc

March 19, 2025 3:22 PM

Maarten Larmuseau of the Laboratory of Human Genetic Genealogy at K.U. Leuven in Belgium traces family trees from archival sources and then invites living members of the family to swab out their mouths to see if their Y-chromosome matches their surname. His research suggests 1% extra-pair paternity (EPP) [leaky paywall Science] aka paternal discrepancy . . . in Flanders. Same story same author Trends in Ecology & Evolution PDF 2016. Rates differ in other cultures.
posted by BobTheScientist (6 comments total)

There is a potentially faulty assumption here; children born to unwed mothers legally had no father and were usually baptised with the mother's surname. In many of these cases the individual with a Y-chromosome discrepancy will still be a descendant of the progenitor of that surname, just not in the male line.
posted by Pseudonymous Cognomen at 3:31 PM on March 19 [3 favorites]

There is a potentially faulty assumption here; children born to unwed mothers legally had no father and were usually baptised with the mother's surname. In many of these cases the individual with a Y-chromosome discrepancy will still be a descendant of the progenitor of that surname, just not in the male line.

As tends to be the case, the researchers very much did consider and account for this: e.g.

"We always verified in the genealogical records that the birth of each child in the patrilineages happened within wedlock and was declared officially by the father himself (for children born after the start of the civil records; after 1800) or that there was clear genealogical evidence that the father was alive when the child was baptized (for children born between 1600 and 1800, when only church records were available)."

posted by kickingtheground at 4:26 PM on March 19 [3 favorites]

"Your mother's your mother, your father maybe."
posted by larrybob at 4:43 PM on March 19

Even in Europe, people regularly make decisions that belie the view that paternity and parenting is primarily a biological investment, including caring for stepchildren, adoption, and fostering. “There’s no genetic kinship there, and people are investing resources in children who are not related to them at all,” Jobling says. “I’m a bit skeptical of applying these sociobiological ideas to human behavior. I think it’s a bit more complicated than that.”

More complicated, indeed. No mention that "paternity" doesn't automatically equate to "parenting" and that throughout history plenty of men who contribute a Y chromosome don't invest resources in children who are related to them.

The researcher estimates 1-2% of EPP in cases of children born to married couples where the husband affirms paternity, historically in Europe...

This 2019 study in the US shows 20% of fathers are "absent", which is to say, not living with any of their children.
posted by Sublimity at 8:13 AM on March 20

I am really surprised at how low that percentage is.
posted by LarryC at 3:09 PM on March 20

Stupid discrepancy Flanders
posted by Ranucci at 5:05 PM on March 20