In a paper published on Thursday, researchers have documented the genetic code of a man who died 4,500 years ago in the place that is presently in Ethiopia, the Washington Post reports.

Earlier studies have mostly been on ancient genomes from Europe, Asia, and the Americas, since Africa's climate is not suited for DNA preservation.

The paper was published in the journal Science.

Scientists say that after the great migration from Africa about 60,000 years ago, some of the Eurasians who had developed agriculture migrated back to Africa. 

Scientists say that the newly sequenced man, named Mota by scientists, lived in Africa before the backwards migration. Therefore, he lacked the Eurasian DNA that seems to have spread across the region about 1,500 years after his death.

"Roughly speaking, the wave of West Eurasian migration back into the Horn of Africa could have been as much as 30% of the population that already lived there - and that, to me, is mind-blowing. The question is: what got them moving all of a sudden?" Andrea Manica , senior author of the study from the University of Cambridge's Department of Zoology, said in a statement.

Scientists compared his DNA to that of modern Africans to predict how large the Eurasian influx had been. 

Manica and his colleagues reported that East Africans owe around 25 percent of their DNA to this Eurasian back flow.  In far Western and Southern Africa, around 5 percent of the genome is Eurasian in origin.