A new paper in Current Biology reiterates what we know, A Historical-Genetic Reconstruction of Human Extra-Pair Paternity:
Paternity testing using genetic markers has shown that extra-pair paternity (EPP) is common in many pair-bonded species…Here, we use a population-level genetic genealogy approach [6, 8] to reconstruct spatiotemporal patterns in human EPP rates. Using patrilineal genealogies from the Low Countries spanning a period of over 500 years and Y chromosome genotyping of living descendants, our analysis reveals that historical EPP rates, while low overall, were strongly impacted by socioeconomic and demographic factors. Specifically, we observe that estimated EPP rates among married couples varied by more than an order of magnitude, from 0.4% to 5.9%, and peaked among families with a low socioeconomic background living in densely populated cities of the late 19th century. Our results support theoretical predictions that social context can strongly affect the outcomes of sexual conflict in human populations by modulating the incentives and opportunities for engaging in extra-pair relationships [9, 10, 11]. These findings show how contemporary genetic data combined with in-depth genealogies open up a new window on the sexual behavior of our ancestors.
The key thing to note that the 5.9% EPP rate is lower than the urban myth often promoted that 10% of children don’t realize the father raising them is not their biological father. The figure at the top illustrates the differences. You see that EPP is higher in low socioeconomic instances. The authors also found that higher density and urban areas were correlated with EPP.
Basically, prosperous farmers in less dense areas are the least likely to exhibit EPP. I think the Dutch study probably generalizes to most Eurasian societies. In particular, the male-dominated peasant societies that emerged in the last 10,000 years have likely been characterized by low EPP. Of course, there are societies with higher rates in the anthropological literature, but as noted in this paper those are societies characterized by more polyandry.