“Media and popular scientific literature often claim that many alleged fathers are being cuckolded into raising children who biologically are not their own,” says Maarten Larmuseau of the KU Leuven Laboratory of Biodiversity and Evolutionary Genomics. “Surprisingly, the estimated rates within human populations are quite low—around 1 or 2 percent.”

Those rates apparently haven’t changed much either, despite the fact that people in the past didn’t have access to modern contraceptives.

When Larmuseau and his colleagues first got started exploring questions of extra-pair paternity (EPP), they were surprised to discover how little hard evidence there was. Nonetheless, the scientific literature frequently suggested that about 10 percent of all children have a biological father different from the alleged one.

But reliable data on contemporary populations that have become available over the last decade, mainly as supplementary results of medical studies, don’t support the notion that 1 in 10 people don’t know who their ‘real’ fathers are. By combining genetics and in-depth genealogies, Larmuseau adds, it’s now even possible to look back at the EPP rates in the historical past. Those data suggest that the rates of EPP haven’t changed much over time.

In 2013, Larmuseau and his colleagues published a report showing low EPP rates within people living in Belgium. However, it wasn’t clear whether those rates were specific to people in that particular part of the world.

“For us, it came as a surprise that several recent studies also estimated historical rates of cuckoldry in other human populations, and came up with equally low estimates in South Africa, Italy, Spain, and Mali,” Larmuseau says.

The findings suggest that any potential advantage of cheating in order to have children who are perhaps better endowed is offset for the majority of women by the potential costs. Those costs likely include spousal aggression, divorce, or reduced paternal investment by the social partner or his relatives.

“The observed low cuckoldry rates in contemporary and past human populations clearly challenge the well-known idea that women routinely ‘shop around’ for good genes by engaging in extra-pair copulations to obtain genetic benefits for their children,” Larmuseau said.

The researchers say that there is likely to be variation in the EPP rate among different groups of people based on various social factors. They plan to conduct future studies to estimate historical EPP rates in human populations with an eye toward factors that shape this limited variation.

Click here to read the study in Trends in Ecology and Evolution. Copies can also be obtained from the authors.

Adapted from the press release issued by Cell Press