A team of researchers traces the contributions of females and males to reproduction
Have females and males contributed equally to the hominid lineage of contemporary populations? Did the ancestors of modern man (Homo sapiens) lean more toward polygamy or monogamy? To answer these questions, Dr. Damian Labuda, an investigator at the CHU Sainte-Justine Research Center and a professor at the Department of Pediatrics of the University of Montreal, and his colleagues have analyzed genomic data from three population samples of African, Asian and European origin. The study’s findings were published in the most recent issue of The American Journal of Human Genetics. Genetic Population History In a strictly monogamous population, one would expect to have an equal number of breeding females and males and, therefore, a breeding sex ratio of 1 female: 1 male. In a population where males tend to have more than one female mate, more females than males contribute to reproduction and, for this reason, the breeding ratio exceeds 1. The authors of this study estimated that the breeding ratio varies between 1.1 and 1.4 according to population: 1.1 in Asia, 1.3 in Europe and 1.4 in Africa. Modern man (Homo sapiens) would, therefore, usually have been monogamous while exhibiting tendencies toward polygamy over the course of evolutionary history. These findings are consistent with studies in evolutionary psychology and anthropology that describe contemporary human populations. An innovative method of analysis To estimate the breeding sex ratio based on genomic data, the authors developed a novel method that makes use of the fact that females carry two X chromosomes, whereas males carry only one. Consequently, during the recombination process, X chromosomes can only exchange their genetic information with females. An excess of breeding women causes an excess of recombination signals in terms of quantifiable X chromosomes. This new method is more reliable than the previous approaches that quantified the breeding ratio using another method. It may be applied to any species for which data on genomic diversity are available.
“ Our results allow better understanding of the genetic population structure, demonstrating once more the importance of population genomics in genetic epidemiology. Being able to analyze the female-male ratio in the history of humans provides new insights into the evolution of our species, which, in turn, leads to better understanding of ourselves through the knowledge of our past,” explains Dr. Damian Labuda.
About the study The article « Female to male breeding ratio in modern humans – an analysis based on historical recombinations» published in the American Journal of Human Genetics was authored by Damian Labuda, Jean-François Lefebvre, Philippe Nadeau et Marie-Hélène Roy-Gagnon, Sainte-Justine University Hospital Research Center, Department of Pediatrics, Department of Social and Preventive Medicine of University of Montreal.
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