Runs of homozygosity suggest a reduction in inbreeding through the Holocene

Gürün K., Altınışık N. E., Gemici H. C., Karamurat C., Koptekin D., Vural K. B., ...More

9th International Symposium on Biomolecular Archaeology (ISBA9), Toulouse, France, 1 - 04 June 2021, pp.96-97

  • Publication Type: Conference Paper / Summary Text
  • City: Toulouse
  • Country: France
  • Page Numbers: pp.96-97
  • Middle East Technical University Affiliated: Yes


How the advent of agriculture and social complexity changed human inbreeding patterns is unclear. Ethnographic work suggests low levels of consanguinity in modern-day foragers compared to farmer communities. Meanwhile, the larger population sizes of farmer societies may have lowered the frequency of panmictic (i.e. drift-driven) inbreeding in these groups. Hence, the net impact of food production on autozygosity levels remains unknown. Here we show that runs of homozygosity (ROH) >1 Mb can be reliably estimated in genomes with ≥3x mean coverage per SNP. We thus calculate the ROH-based inbreeding coefficient estimate, or FROH, in 411 published ancient Eurasian genomes from the last 15,000 years. We find that FROH has significantly decreased over time, in both West and Central Eurasia. The most dramatic reduction appears associated with the Neolithic Transition. Our results hence suggest that population growth caused by food production, along with increased rates of human mobility, reduced the frequency of panmictic inbreeding and led to a reduction in overall autozygosity. We find that cases of high consanguinity are rare in our sample and are restricted to individuals from farmer communities. Finally, we note that the high consanguinity levels observed in presentday Central Eurasia are not observed in ancient genomes, and this may therefore be a recent phenomenon.