All Humans Originated From a Single Population from Africa, DNA Study Suggests

A new study, led by researchers at Harvard Medical School, involving modern DNA collected around the world revealed that the genetic ancestry living outside Africa came from a single population that migrated out of the continent.

The study, published in the journal Nature, suggests that genetic ancestry of all non-Africans can be traced back to a single population emerging from the continent between 50,000 and 80,000 years ago. However, another study, published simultaneously in the journal Nature, suggests that a small percent of the DNA in modern non-Africans came from a population in Africa that left the continent about 120,000 years ago.

"Our best estimate for the proportion of ancestry from an early-exit population is zero," said professor of genetics at HMS and senior author of the study, in a press release. "Taken together, all three studies leave wiggle room for, at most, around two percent."

For the HMS study, the researchers analyzed the genomes of 300 people from 91 indigenous groups that include diverse Native American, South Asian and African populations. They then compared the genomes to two other genomes selected from 51 populations represented in a collection called the Human Genome Diversity Project.

The researchers found out that the vast majority of modern human ancestry in non-Africans derives from a single population that migrated out of Africa. This conclusion is supported by two other studies. One of the studies, led by an Estonian group, focused on 379 whole genome sequences, while the other, led by a Danish group, concentrated on 108 genomes from Australia and New Guinea.

Furthermore, the HMS researchers discovered that the common ancestors of modern humans began to differentiate about 200,000 years ago, long before the migration out of Africa occurred.

The study, however, did not provide conclusive evidence to determine if the group that left Africa represented a large subset of the populations within the continent, suggesting that there is a lot of substructure within the population in Africa prior to the expansion.