Insights in the adaptive character of extra-pair paternity behaviour across human Western populations

When the caring and official father is not the biological one, a so-called extra-pair paternity (EPP) event occurs. After decades of speculation and many false or highly biased claims, data on EPP frequencies within contemporary human populations became available in the last decade. Although highly relevant for biologists, social scientists and forensic geneticists, estimations of EPP frequencies in past populations still remain controversial due to the lack of valid data, conceptual clarity, and interdisciplinary collaboration. Recently, an innovative pilot study was able to calculate past EPP frequencies by comparing Y-chromosomal variation between assumed patrilineally related men. The estimated frequency was a mean value for a single population in the last 400 years which, however, can differ across other (Western) populations due to evolutionary, cultural and sociodemographic factors. Therefore, the main aim of this project is to get insights into the range of historical EPP frequencies in Western societies by enlarging the recently developed approach to calculate and interpret past EPP rates with samples from the Netherlands, UK, Spain, Italy and Australia. The combination of concepts and state-of-the-art methodologies from three disciplines, namely human behavioural ecology, historical demography and forensic genetics, will lead to the realisation of this objective as well as provide new insights into each discipline.