In the 1980s, a group of scientists put forth a hypothesis stating that around 50,000 years ago, a single exodus from Africa resulted in modern man populating the whole world. Scientists led by Harvard Medical School geneticists analyzed DNA cultures from around the world and concluded that the hypothesis stands true.
The modern Homo sapiens evolved in Africa nearly 200,000 years ago. How they populated the rest of the world had always intrigued scientists. A series of studies published Wednesday in the journal Nature analyzed hundreds of DNA samples and found that though the genetic ancestry of people living outside Africa was a result of the one exodus that occurred 40,000 to 80,000 years ago, some native islanders in the southwestern Pacific Ocean can be traced to an earlier exodus.
“I think all three studies are basically saying the same thing,” Joshua M. Akey from the University of Washington, who co-wrote a commentary accompanying the findings, said. “We know there were multiple dispersals out of Africa, but we can trace our ancestry back to a single one.”
The three studies by three different international teams sequenced the genomes of nearly 787 people from hundreds of indigenous populations including Basques, African pygmies, Mayans, Bedouins, Sherpas and Cree Indians.
The human DNA undergoes changes over time and analyzing these changes can give an estimate of when two populations split from each other.
One of the studies found that the ancestry of the natives of Papua New Guinea, north of Australia, could be traced back to an earlier migration that occurred 120,000 years ago. The study analyzed DNA samples of 483 people belonging to 148 populations from around the world.
The researchers from the Estonian Biocenter concluded that all people in Papua New Guinea carry a trace of DNA from the earlier exodus. However, the researchers found that when the last wave of humans emerged from Africa, the descendants from the first had vanished. The other two papers found that the genetic contribution of early migrations would be tiny.
“They may have not been technologically advanced, living in small groups,” Luca Pagani, co-author of one of the studies from the University of Cambridge and the Estonian Biocenter, reportedly said. “Maybe it was easy for a major later wave that was more successful to wipe them out.”