Human ancestors went from Africa to the world

Modern humans first appeared in sub-Saharan Africa about 200,000 years ago. For a long time, there has been much controversy about the timing and process by which modern humans crossed the Sahara and made their way out of Africa. Previous studies have suggested that modern humans moved out of Africa on a large scale between 70,000 and 40,000 years ago. However, a recent study suggests that modern humans may have started their journey to the world as early as 130,000 years ago, and subsequently expanded out of Africa several times.

Scientists used to believe that modern humans had two routes out of Africa. One, known as the northern route, saw humans leave Africa through what is now Egypt and the Sinai Peninsula; the other, known as the southern route, saw humans leave from what is now Ethiopia and the Arabian Peninsula. Both migratory routes lack adequate and reliable evidence.

To figure out which route modern human ancestors might have taken when they left Africa, the researchers sequenced the genomes of 225 people (Including 100 Egyptians and 125 Ethiopians) in northeastern Africa. They then matched these data with East Asians (Specifically Han Chinese), South Asians (Gujaratis in India), and Europeans (Tuscans in Italy), respectively. In addition, they matched the data with modern sub-Saharan West Africans whose genes can broadly reflect the gene pool of ancient sub-Saharan humans. 

The scientists noted that modern Egyptians and Ethiopians have recently experienced a history of migration from outside Africa, and the resulting mixing may have increased the genetic similarity between them and those who moved to Africa. With this in mind, the researchers eliminated all genetic sequences that could have come from recent immigrants.