In 2012, an archaeological team funded by the National Science Foundation and led by Kathryn and John Arthur (both of the University of South Florida St. Petersburg) and Matthew Curtis (Ventura College and UCLA Extension), excavated Mota Cave in the Gamo Highlands of Southwestern Ethiopia and recovered a 4,500-year-old male human skeleton that has provided the first complete ancient human (Homo sapiens) genome sequenced from the African continent. Jay Stock (University of Cambridge) conducted the skeletal morphological analysis and Andrea Manica (University of Cambridge) and Ron Pinhasi (University College Dublin) headed a team responsible for the DNA sequencing and analysis. The results of this research were recently published in Science.
The archaeologists have given the ancient man of Mota Cave the name Bayira, meaning “first born” in the Gamo language. Bayira’s skeleton and the archaeological record associated with him provide an opportunity to examine ancient regional and inter-regional population dynamics. Bayira predates a Eurasian gene flow into parts of north-eastern Africa that seems to have occurred after 3,000 years BP, and provides a relatively unadmixed African genomic reference for exploring issues related to the initial movement of Homo sapiens “out-of-Africa” and much more recent demographic events.
By analyzing Bayira as an unadmixed reference, the Cambridge geneticists have demonstrated a significant level of western Eurasian admixture in genomes throughout the African continent, which is similar to Neolithic (LBK) genomes in Europe. The mechanisms by which this happened are unclear, but may have been due to gene flow related to specific population interactions in the Southern Red Sea area or elsewhere in Northeastern Africa followed by gene flow among African populations across the continent. Archaeological and epigraphic evidence does suggest that beginning about 3000 years BP interaction between polities in the northern Horn of Africa and the Southern Arabian Peninsula intensified and new forms of sociopolitical and economic organization appeared, perhaps as a consequence of this interaction.
The DNA of Bayira also offers insights into prehistoric adaptation to life in the Ethiopian highlands. Bayira’s genotype contained three genetic variants, common among modern highland people in Ethiopia today, which provide adaptation to the low oxygen conditions of high altitude. Bayira also helps us begin to piece together the population history of Southwestern Ethiopia. Bayira is genetically closest to the Ari ethnic group, an Omotic-speaking society living in Southwestern Ethiopia today. Currently, no living people from the Gamo Highlands (where Bayira lived) have been genetically sequenced for comparison, so future research will be required to fully understand the genetic relationships between Bayira and people living in the Gamo Highlands today. The Omotic languages are linguistically the most divergent of the Afroasiatic language phylum, suggesting that Omotic speakers may have lived in Southwestern Ethiopia for a long and sustained period of time. The 4,500-year-old Bayira and his connection to living Omotic-speaking peoples may lend support to this view.
Kathryn W. Arthur, John W. Arthur, Matthew C. Curtis, Jay T. Stock