Historically, cuckoldry rates have been remarkably low in many societies around the world.
Though popular belief holds that 10-30% of children are the product of female infidelity, recent genetic research shows the rate is actually around 1-2%.
This challenges the notion that women frequently have affairs to obtain “good genes” for their offspring.
Key Facts:
- Contemporary estimates of 10-30% cuckoldry are likely biased by reliance on disputed paternity cases. Studies of general populations find rates of 1-2%.
- Genetic research on historical cuckoldry rates also point to 1-2% across several societies over the past 300-500 years.
- Low rates held even before modern contraceptives, countering the belief that contraceptives enabled more adultery without as much cuckoldry.
- Mostly steady rates over centuries suggest genetic benefits of affairs seldom outweigh costs like potential invested partner disinvestment in offspring.
Quantifying Cuckoldry Rates with Genetic Testing
For years, many accepted unsupported high estimates of cuckoldry due to female affairs.
These came from sources like paternity test labs and evolutionary theory about genetic benefits of affairs.
However, it was challenging to estimate rates accurately before genetic paternity testing.
Now researchers can compare ancestry-informative gene variants, like those on the Y chromosome, between supposed male family members.
Mismatched variants reveal cases of cuckoldry.
Several studies have done this using genealogical records to identify related men and test their Y chromosomes.
The Seminal Dogon Village Study
A pioneering study analyzed Y chromosomes of Dogon villagers in Mali with known family relationships per oral histories.
This found a cuckoldry rate of 1.8%, lower than expected.
The oral genealogies may even have exaggerated mismatches between “relatives.”
Still, this study demonstrated the potential of genetics to illuminate historical cuckoldry.
Expanding the Methodology in Belgium
Follow-up European research refined the methodology by utilizing extensive written genealogical records.
Studying Flanders, Belgium this way yielded an estimated cuckoldry rate of 0.9% over the past 500 years.
The researchers also developed an independent estimate of 0.9% using surnames as ancestry markers.
Consistent Low Rates Across Cultures
Other groups extended genetic genealogy techniques to additional populations.
Rates remained low, including:
- 0.9% over 300 years in Afrikaners in South Africa
- 1.2% over 400 years in Northern Italians
- 0.6-1.7% over centuries in Catalonia, Spain
Rates climbed above 10% only in specific cases like lower socioeconomic status families or cultures with partible paternity beliefs.
But overall, low 1-2% rates persisted across divergent human societies for hundreds of years.
Stability Through the Ages
Low rates staying steady for centuries fly against the belief that cuckoldry would have been rampant without modern contraceptives.
Surprisingly, the ability to conceal affairs did not translate to high cuckoldry when looking back genetically.
This contrasts with evolutionary hypotheses that females frequently “shop around” for better genes.
The rare examples of higher cuckoldry also argue against the notion that women evolved to commonly employ it to diversify offspring genetics.
Reconsidering the Costs and Benefits of Affairs
The lack of change over time implies the costs of cuckoldry typically outweighed potential genetic benefits for offspring.
Costs may include:
- Sexually transmitted infection risk
- Loss of paternal care if discovered
- Partner aggression over infidelity
Long human child dependency and paternal investment mean one man’s support matters greatly.
Even occasional cuckoldry could endanger this if revealed.
Genetic advantages for a minority of offspring may simply be insufficient to offset massive costs.
This fits with evidence that extra-pair mating lowers offspring fitness in some monogamous species too.
And various cultural practices like sexual jealousy or stigmatizing female adultery may have adapted to deter cuckoldry.
Overall, the risks seem to curtail its regular use for genetic “shopping” among women.
Cuckoldry in Specific Populations
That said, some populations depart from 1-2% norms. Higher cuckoldry associates with:
- Poverty – some evidence suggests over 20% more cuckoldry in lower socioeconomic status Mexican families
- Belief in partible paternity – rates near 10% in some Amazonian societies where children can have multiple social fathers
So culture and environment may modulate cuckoldry frequency, but a low baseline rate perseveres across most environments.
This contrasts with birds, where around 10% of offspring come from extra-pair mating.
Future Research Directions
More studies of historical cuckoldry rates will clarify the evolutionary and cultural factors that affect its prevalence across different groups.
This can aid other fields like medicine and forensics that rely on accurate pedigrees.
It also will enable population genetic modeling of how sexually transmitted infections spread.
In particular, comparing contexts that raise or lower cuckoldry will shed light on why it remains rare.
If certain practices successfully reduced its occurrence, they may explain thepersistence of low rates.
Ultimately, cuckoldry frequency represents an evolutionary balance of costs versus benefits that varies across settings.
Conclusion: Low rates of cuckolding
While cuckoldry captures popular imagination, genetic testing reveals it was evolutionarily uncommon for women to employ it for genetic benefits.
Centuries-long consistency in rates argues against high cuckoldry without modern contraceptives.
Cuckoldry’s rarity despite women’s ability for surreptitious affairs highlights underestimated costs outweighing genetic incentives.
Going forward, pinpointing factors that alter cuckoldry rates will elucidate the evolutionary logic behind its judicious use in our ancestry.
References
- Study: Cuckolded fathers rare in human populations
- Authors: Maarten H.D. Larmuseau et al. (2016)
