Population Research Institute

Whether and how Darwinian selection has influenced human evolution after the agricultural revolution remains controversial. A key stumbling block to the study of evolution in more modern human populations has been the limited availability of suitable datasets. A new result from the research project “Reproductive behavior in contemporary societies” by Alexandre Courtiol et al. used church records of nearly 6000 Finnish people born from 1760-1849 to determine whether the demographic, cultural and technological changes of the agricultural revolution curtailed natural and sexual selection in our species. With information on individuals’ wealth status, births, deaths, and marriages, the researchers studied the contributions of four episodes of selection during the life cycle: survival to adulthood, mate access, mating success, and fertility per mate. The researchers found that the intensity of Darwinian selection in the farming and fishing-based populations was on par with the opportunity for selection in other species. The analysis suggested that differences in early survival and fertility were responsible for most variation in fitness, even among wealthy individuals. Although monogamy limited the potential for selection, all requirements for sexual selection to operate were still met, the researchers found. The results suggest that researchers can no longer assume that all human populations have remained unaffected by selection for the last millennia, according to the authors. PNAS Article #11-18174: “Natural and sexual selection in a monogamous historical human population," by Alexandre Courtiol, Jenni Pettay, Markus Jokela, Anna Rotkirch, and Virpi Lummaa