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Genome Sequencing Of 4,500-Year-Old African DNA Helps Solve Mystery Of Ancient Mass Migration

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A DNA analysis of an ancient skull retrieved from Ethiopia has allowed scientists to uncover information regarding a large migration of West Eurasians into the African continent some 3,000 years ago.

In a study featured in the journal Science, researchers from the University of Cambridge conducted the first ever genome sequencing of a 4,500-year-old DNA. The sample was taken from the skeletal remains of an individual found in the Mota cave located in Ethiopia's highlands, where the conditions were dry and cool enough to preserve the genome for thousands of years.

Genome Sequencing

According to the researchers, the ancient DNA sample predates an event known as the Eurasian backflow occurred around 3,000 years ago wherein a large number of people from Western Eurasia, including those living in Anatolia and the Near East, migrated back into the Horn of Africa.

The sequencing of the genome allowed the Cambridge scientists to carry out a genetic comparison spanning thousands of years and find out that these Western Eurasians were a close relative of the famers in the Early Neolithic era responsible for bringing agriculture to the European continent 4,000 years ago.

Comparisons of the prehistoric genome to those of present-day Africans showed that people living in East Africa today are up to 25 percent Eurasian in their ancestry as a result of the Eurasian backflow event, while African populations located in different parts of the continent have at least five percent of their DNA traceable to this ancient migration of Eurasians.

Eurasian Backflow

The recent findings offer evidence that the Eurasian backflow event had a far larger extent and more influence to the people of Africa than what was initially thought. The researchers believe that this massive movement was likely the equivalent of more than a quarter of the total population in the Horn of Africa at the time, which reached the region and eventually dispersed across the entire continent genetically.

Dr. Andrea Manica, a researcher at Cambridge's zoology department and senior author of the study, explained that the number of people involved in the Eurasian backflow is roughly about 30 percent of the then population of the region. She said that the question that needs to be answered now is what caused these people to suddenly migrate.

Earlier studies on prehistoric genetics in Africa have tried to sift through the genomes of modern populations and eliminate present-day influences.

Manica said that the ancient genome provides them with a window into history, where a singular DNA from an individual can help them create a picture of an entire race of people.

Scientists have attempted to identify the cause of the Eurasian backflow event, including studying potential climatic factors, but it continues to be a scientific mystery.

Evidence taken from archeological finds, however, suggests that the migration of the Western Eurasians coincided with the introduction of Near Eastern crops, such as barley and wheat, into the East African region. This shows that migrants from other areas could have aided the development of new agricultural practices in the area.

The Cambridge scientists note that the migrants from Western Eurasia were either close relatives or direct descendants of Neolithic farmers that had introduced the concept of agriculture to West Eurasia some 7,000 years ago. These ancient farmers then moved back into the Horn of Africa around 4,000 years afterward.

Trinity College Dublin geneticist Eppie Jones, who led the team in carrying out the genome sequencing of the ancient DNA, said that while the Near East underwent a change in its genetic makeup throughout the course of thousands of years, the scientists believe that the closest present-day equivalents to these Neolithic farmers are the Sardinians. This is likely because the island of Sardinia has been isolated from other continents.

Jones said that the ancient migrants found their way to the island and created some sort of time capsule, which caused the ancestry of Sardinians to become the closest to that of populations in prehistoric Near East.

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