1 Kempenaers B.

Verheyen G.R.

Van den Broeck M.

Burke T.

Van Broeckhoven C.

Dhondt A. Extra-pair paternity results from female preference for high-quality males in the blue tit.

2 Gray P.B.

Anderson K.G. Fatherhood: Evolution and Human Paternal Behavior.

3 Kempenaers B.

Schlicht E. Extra-pair behaviour.

4 Griffith S.C.

Owens I.P.F.

Thuman K.A. Extra pair paternity in birds: a review of interspecific variation and adaptive function.

5 Platek S.M.

Shackelford T.K. Female Infidelity and Paternal Uncertainty: Evolutionary Perspectives on Male Anti-Cuckoldry Tactics.

2 Gray P.B.

Anderson K.G. Fatherhood: Evolution and Human Paternal Behavior.

6 Larmuseau M.H.D.

Matthijs K.

Wenseleers T. Cuckolded fathers rare in human populations.

7 Larmuseau M.H.D.

Matthijs K.

Wenseleers T. Long-term trends in human extra-pair paternity: increased infidelity or adaptive strategy? A reply to Harris (2016).

6 Larmuseau M.H.D.

Matthijs K.

Wenseleers T. Cuckolded fathers rare in human populations.

8 Larmuseau M.H.

Vanoverbeke J.

Van Geystelen A.

Defraene G.

Vanderheyden N.

Matthys K.

Wenseleers T.

Decorte R. Low historical rates of cuckoldry in a Western European human population traced by Y-chromosome and genealogical data.

9 Scelza B.A. Choosy but not chaste: multiple mating in human females.

10 Hrdy S.B. The optimal number of fathers. Evolution, demography, and history in the shaping of female mate preferences.

11 Gangestad S.W.

Simpson J.A. The evolution of human mating: trade-offs and strategic pluralism.

Paternity testing using genetic markers has shown that extra-pair paternity (EPP) is common in many pair-bonded species []. Evolutionary theory and empirical data show that extra-pair copulations can increase the fitness of males as well as females []. This can carry a significant fitness cost for the social father, who then invests in rearing offspring that biologically are not his own []. Inextra-pair paternity remain highly contentious []. Here, we use a population-level genetic genealogy approach [] 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 19century. 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 []. These findings show how contemporary genetic data combined with in-depth genealogies open up a new window on the sexual behavior of our ancestors.