All humans came from Africa in a single wave

Dispersal Took Place 50k-80k Years Ago

Modern humans evolved in Africa roughly 2,00,000 years ago. But how did our species go on to populate the rest of the globe?

In a series of genetic analyses published on Wednesday in journal Nature, researchers believe they have found an answer to the question that has intrigued scientists for decades. Three separate teams of geneticists surveyed DNA collected from cultures around the globe, and concluded that all non-Africans today trace their ancestry to a single population emerging from Africa between 50,000 and 80,000 years ago.

“We know there were multiple dispersals out of Africa, but we can trace our ancestry back to a single one,“ said Joshua Akey of University of Washington. The three teams sequenced the genomes of 787 people, drawn from people in hundreds of indigenous populations: Basques, African pygmies, Mayans, Bedouins, Sherpas and Cree Indians.

The DNA of indigenous populations is essential to understand human history , many geneticists believe. The new data has altered scientific understanding of what human DNA looks like, experts said.

In the 1980s, a group of paleoanthropologists began championing a hypothesis that modern humans emerged only once from Africa, roughly 50,000 years ago. Skeletons and tools discovered indicated that modern humans lived after that time in Europe, Asia and Australia. Yet there are also clues that some humans may have departed Africa well before 50,000 years ago.

In Israel, for example, researchers found a few distinctive ly human skeletons that are between 1,20,000 and 90,000 years old. In Saudi Arabia and India, sophisticated tools date back as far as 1,00,000 years. Last October, Chinese scientists found tooth belonging to Homo sapiens that were 80,000 years old.

In 2011, Eske Willerslev, a renowned geneticist, reconstructed the genome of an aboriginal Australian for the first time from a century-old lock of hair. The DNA held a number of peculiar variants not found in Europeans or Asians, raising questions about the origins of the people who first came to Australia and when they arrived.Meanwhile, Mait Metspalu of the Estonian Biocentre picked out 148 populations to sample, mostly in Europe and Asia, with a few genomes from Africa and Australia.They , too, sequenced 483 genomes. David Reich, a geneticist at Harvard Medical School, and his colleagues assembled a third database of genomes from all six inhabited continents.

All three groups came to the same conclusion: People everywhere descended from a single migration of early humans from Africa. But they found no genetic evidence that there was an earlier migration giving rise to people in Australia and Papua New Guinea.

(TOI)