Identical by Descent (IBD): Investigation of the Genetic Ties between Africans, Denisovans, and Neandertals

Abstract

Interbreeding between human ancestors and other hominins has been extensively studied outside of Africa, but their shared history within Africa has received less study. However, comprehending subsequent events outside of Africa requires shining light on human evolution during this period, about which little is known. We investigate the genetic relationships of humans. By finding relatively short DNA sequences that these hominins share in the 1000 Genomes Phase 3 data, researchers were able to distinguish between African, Neandertals, and Denisovans descent by identical (IBD). It was confidently detected very short IBD segments by focusing on low frequency and uncommon variations. These segments reflect occurrences from the distant past because small IBD segments are likely older than larger ones. There have been two types of very old IBD segments found that are shared by humans, Neandertals, and/or Denisovans. Longer segments are more common in Asians and Europeans, with more segments in the South. Asians exceed East Asians in both Neandertal and Denisovan cultures. These longer portions indicate complex admixture occurring outside of the admixture events. Africa, the second category comprises shorter pieces that are largely shared among Africans and hence may depict African-related events.