Tracing the ancestry of Middle East populations

A new study of the genetic make-up of the Levant shows that many inhabitants can trace their ancestry back to an African male and a European mother.

The Middle East was a gateway through which humans not only funneled out from Africa, but which witnessed multiple back and forth migrations over more recent millennia: in and out of Africa, as well as through to Europe and the Arabian Gulf.

According to a recent study published in PLoS One, the complex genetic structure of the region suggests that modern day inhabitants of the Levant have African male ancestors and Europeans female ancestors¹.

During migrations out of Africa about 20 millennia ago, females didn't always migrate with their male partners into North Africa. However, most males accompanied their female partners during their exodus to Europe.

The researchers discovered these peculiar aspects of prehistoric human migration by studying Y-chromosome and mitochondrial DNA (mtDNA) isolated from the blood samples of modern humans living in the Middle East, Africa and Europe.

The genes on both Y-chromosomes and mtDNA rarely accumulate mutations over thousands of generations and carry intact clues to prehistoric human activities such as migrations. The Y-chromosome genes are inherited from fathers and can trace back to our prehistoric fathers. Likewise, mothers pass on mtDNA to their offspring, leading us to our single prehistoric mother.

The Y-chromosome analysis results suggest that Middle Easterners harbour a gene pool with greater affinity to African fathers. The mtDNA of the Middle Eastern population, however, did not show affinity to Africa. This suggests that when males migrated into North Africa, they left their female companions behind.

The mtDNA analyses of individuals from modern day Lebanon, Syria, Jordan, and some regions of Iraq and the Sinai Peninsula in Egypt revealed stronger affinities to Europeans with little influence from the Arabian Peninsula.

Migration patterns

"This is the strongest point of the research," says Pierre Zalloua, a geneticist at the American University in Beirut and a senior co-author of the study. It shows that current day inhabitants of the Levant share "an African father and a European mother."

Zalloua adds that migration direction " is from Africa to the Levant and then to Europe with many male migrations in between. The maternal European affinity is the best example of female migration from the Levant to Europe during the New Stone age."

The study provides the broadest survey of Y-chromosome and mtDNA contrast in North and sub-Saharan Africa, Europe and Middle Eastern populations. Contrasting the findings from the various regions suggested the difference in migration patterns of humans going to North African and to Europe.

"It is a very impressive sample and a rather complex dataset," says Peter Underhill from the Stanford University School of Medicine, Stanford, US.

The study results, he adds, befit the complex history associated with the Middle East, which is challenging to disentangle.

While Lebanon's mtDNA shows a very strong association with Europe, Yemenis mtDNA showed close affinity to Egypt and North and East Africa.

This relation dates back to the 7th millennium B.C. when empire expansions and trade, including the slave trade, heavily influenced genetic migration between Yemen and East Africa. The expansion of trade through the Red Sea and into the Indian Ocean basin starting also provided the largest opportunities for genetic transfers from Africa into Yemen.

Peter Forster from the University of Cambridge says, "The unsolved challenge is to apply a molecular clock to the genetic data, especially the Y-chromosome data, to calculate when men and women from the Middle East migrated in prehistory to North Africa and Europe and reveal the culture of these migrants."

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