Curious

Ancient boy’s DNA Pushes Back Date of Earliest Humans

Nearly 2.000 years ago, a boy who lived on what is now South Africa, has lend a helping genome to science. Using this child’s genetic instruction book, it was estimated that human race emerged as a distinct population much earlier than previously thought.

Scientist retrieved a complete version of the ancient’s boy DNA from his skeleton and compared it to DNA from people today, also from the Stone Age Neanderthals and Denisovans.

Researchers published a report not long ago that documented migrations of West African farmers to East Africa, which reshaped Africans’ genetics more than it has been known.

“Unexpectedly the boy’s DNA was not affected by these migrations, and this discovery provided the best benchmark so far for gauging when Homo sapiens originated in Africa”, evolutionary geneticist Carina Schlebusch of Uppsala University in Sweden and her colleagues conclude.

Some researchers proposed a theory that 300,000-year-old fossils found in northwestern Africa belonged to H. Sapiens.They suspect that a skull from South Africa’s Florisbad site, dated to around 260,000 years ago, qualifies as H. sapiens. However, our species’ origin is usually placed close to 200,000 years ago.

The boy’s remains came from previous shoreline excavations near the town of Ballito Bay, but the debate over the timing of our ancestors will not stop, despite the new evidence.

ANCIENT SPLITS

In the diagram above, based on this new DNA study, H. Sapiens originates between 350,000 and 260,000 years ago. African populations shown on the chart divide in two separate directions and then around 200,000 years ago further subdivide. Non-African populations, bottom left, appeared shortly after 100,000 years ago.

Further mixing of populations had a big genetic impact. Harvard Medical School evolutionary geneticist, Pontus Skoglund, says that DNA evidence from more recent fossils, suggest that Stone Age human groups migrated from one part of Africa to another and mated with each other along the way.

A few months ago, DNA from sixteen Africans whose remains date to between 8,100 and 400 years ago, revealed a shared ancestry among hunter-gatherers from East Africa to South Africa who first arrived 2,000 years ago.

Skoglund’s group found out that the ancient set of common genes still comprises a big, varying chunk of the DNA of present-day Khoisan people in the southern parts of Africa. Previous studies discovered that the Khoisan show more genetic diversity than any other human population.

It’s estimated that a genetic split between the Khoisan and other Africans occurred around 260,000 years ago, shortly after humankind’s Khoisan people, then diverged into two genetically distinct populations.

These comparisons indicate that 9 to 30 percent of today’s Khoisan DNA comes from an East African population that had already interbred with Eurasian people. These people were likely the farmers who started out in West Africa and reached southern Africa around 1,500 years ago, the researchers propose.

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