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New insights into earlier waves of Back-to-Africa migrations

Published online 30 June 2014

Pakinam Amer

Some recent genomic studies suggest that non-African admixture in the Horn of Africa (HOA) region occurred primarily about 3,000 years ago, but new research suggests the move might have come much earlier1

Scientists generated new genome-wide short nucleotide polymorphism data from 61 Yemenis, representing all geographic regions of the country, and merged them with published data from the HOA, the Middle East, North Africa, Qatar, southern and western Africa in addition to the HapMap3 project and the Human Genome Diversity Project. Their analysis of these data indicates the majority of admixture in the HOA (mainly Ethiopia, Eritrea, Djibouti and Somalia) probably occurred before the advent of agriculture. 

The scientists were able to investigate the discrepancy among the archaeological, historical, mitochondrial, Y chromosome and genome-wide data for recent evidence of ancient evidence of admixture in the HOA. 

They determined, according to lead author Ryan Raaum, Assistant Professor in the Department of Anthropology at Lehman College & the Graduate Center, City University of New York, that there were probably multiple migrations — with the largest coming from an ancient population that separated from all other non-African populations by as early as 23,000 years ago. 

The last few hundred years are believed to be exclusively marked by heavy migration and admixture because of increasing international trade, but “these results contribute to a growing body of work showing that prehistoric hunter-gatherer populations were much more dynamic than usually assumed,” according to the study, which was co-authored by Ali Al-Meeri from Sana'a University, Yemen, and published in PLOS Genetics


  1. Hodgson, J. A., Mulligan, C. J., Al-Meeri, A. & Raaum, R. L. Early Back-to-Africa migration into the Horn of Africa. PLoS Genet. 10, e1004393 (2014).