DNA sequencing reveals how early humans spread in Africa

The khoisan people, who live in southern Africa, have long been isolated from other African populations, but carry DNA from the herdsmen of eastern Africa.

The study of ancient human DNA is not an equal opportunity effort.

In the past 10 years, parts of the genome of early europeans and asians have been sequenced hundreds of times, and the history of Eurasia has been rewritten in the process.

However, because genetic material decays very rapidly in warm, humid climates, scientists have today only sequenced the DNA of an ancient African human.

Recently, Austin, Texas in the United States at the annual meeting of the molecular biology and into the chemical society, scientists announced that they have been part of the genome sequencing 15 ancient africans, samples from sub-saharan Africa as a whole.

At the same time, another group sequenced seven ancient humans from South Africa, although the research has yet to be published.

"Finding an ancient genome from Africa is a remarkable thing."

"Anna Sapfo Malaspinas, a population geneticist at the university of Bern in Switzerland, who was not involved in any of the studies.

Africa has long been called the cradle of mankind.

About 50,000 years ago, early human ancestors spread from Africa to other parts of the world.

Africa is also the most diverse place for ancient and modern genes.

But how the ancient population, from the hazaza people of East Africa to the southern African community of khoisan, formed, has been a mystery.

That is partly because the early agricultural adopters, known as Bantu, spread across the continent about 2,000 years ago, wiping out the genetic footprints of other africans.

The ancient African genome, which had been sequenced, came from an Ethiopian living about 4,500 years ago, but it could not solve the puzzle.

Pontus Skoglund knows there's more to this story.

To that end, the evolutionary geneticist and colleague from Harvard University has captured the DNA of 15 ancient africans who lived between 6,000 and 500 years ago, some of them before the Bantu expansion.

In addition, Skoglund team also obtained from Africa 19 modern human DNA data for comparison, including large crowds and like Bantu people like him, the same as the khoisan a smaller population.

In most cases, Skoglund reported, ancient DNA was most similar to human DNA in the same places where bones were found.

However, some interesting exceptions show the mixing of different groups.

"It's nice to see this mix of ancient people in Africa."

"There must have been a movement of people in early Africa," says Simon Aeschbacher, a population geneticist at the university of Bern who was not involved in the study.

Ancient genome shows that people living in South Africa in the crowd out of thousands of years ago from west Africa, and then evolved in the hone their taste buds and the key to protect them from sun damage ability to adapt.

About 3,000 years ago, it was possible that the herders in Tanzania had spread and had arrived in southern Africa hundreds of years before the earliest farmers appeared.

However, Skoglund argues that modern malawians living in southern Tanzania may be farmers living in western Africa rather than local hunter-gatherers.

Indeed, analysis shows that western africans are early contributors to DNA from sub-saharan African populations.

But even the "donors" of the DNA are now a "hodgepodge" of two modern groups, the mendi and the yorubba.

At the same time, an ancient African herdsman showed his influence from farther afield.

Research shows that 38% of its DNA comes from outside Africa.

Another study focused on southern African populations.

Researchers believe that modern homo sapiens evolved there.

Carina Schlebusch, an evolutionary geneticist at uppsala university in Sweden, and colleagues sequenced seven ancient genomes: three hunter-gatherers from 2000 years ago, and four farmers from 500 to 300 years ago.

The researchers also included modern DNA in their analysis.

Although the more modern farmer's genome has a Bantu DNA, ancient hunter-gatherers existed earlier than Bantu's expansion.

Last month, Schlebusch and colleagues reported the results on bioRxiv, a life science pre-print site.

Their findings are similar to those of Skoglund: the farmers' modern descendants (including those in the southern africana) 9% to 22% of their DNA from eastern African and Eurasian herders.

Schlebusch analysis compared with those of Skoglund research more deeply explores the human history, because she's team used the ancient and modern genome estimates, the research of hunting - gatherer - the equivalent of about 260000 years ago the oldest fossil homo sapiens "age", was isolated from the rest of the population.

Harvard evolutionary geneticists Iain Mathieson said, get this date "let's start thinking like in May be called the modern human anatomy and behavior where and how people evolved".

It remains to be seen whether this date can withstand peer review after the paper is published.

Aeaschbacher has a simple solution to this uncertainty: sequencing the older African genome.

How ancient africans were divided into different groups and when and how they moved "will have a powerful influence on what modern humans are."

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