One of the main pillars of the “outside Africa” ​​model of human origin is the events that took place outside the African continent. According to this model, about 60,000 years ago, our species left Africa and through an epic cleansing populated Eurasia.

But the “cracks” in this model, have become bigger and bigger with the passage of time. For example, human skulls discovered in two areas in Israel are 120,000 years old. They are often cited as evidence that before the mass exodus, mankind made several brief but failed attempts to establish itself in West Asia.

But developments over the years suggest that there were in fact more than just sporadic efforts. For example, a 177,000-year-old jaw found in the Mislija Cave in Israel suggests that there was a much older human presence in the Middle East that lasted longer.

But the most surprising discovery came last year, when two skulls discovered in Greece in 1978 finally revealed some of their secrets. They were found in the Apidima coastal cave, glued to each other from behind, through an amalgam of frozen volcanic lava.

It was originally thought that both skulls belonged to the Neanderthals and were about 150,000 years old. But a re-analysis showed the opposite. One of them really belonged to a 170,000-year-old Neanderthal. But the other was 210,000 years old and came from a Homo sapiens, albeit with a mix of modern and archaic features.

The skulls had somehow ended up in the same part of the cave, and had clung to each other some time later. The only conclusion is that the first modern humans to live in Africa more than 200,000 years ago were successfully distributed in Southern Europe.

This long journey was made on foot, or perhaps more widely around the Eastern Mediterranean, which probably lasted for thousands of years. “This is a very surprising discovery,” said Kris Stringer, an expert at the Natural History Museum in London who was part of the team that performed the analysis.

Evidence of earlier human distribution has been found even further away from Africa. In 2015, researchers in China announced the discovery of modern human teeth in a cave in the south of the country, dating back at least 80,000 years. Several other fossils dating to almost the same period have been found in China.

They are conventionally classified as Homo erectus, the first member of our genus to walk upright, but now it seems more likely that they belong to Homo sapiens, says Maria Martinon-Torres of the National Research Center. of the Human Evolution (CENIEH) in the Prison of Spain. “They were there!” She says. Stringer also agrees: “If they came to Europe, I see no reason why they didn’t go to China.”

These new discoveries of early distributions of modern humans are very intriguing. But the main picture remains essentially unchanged. Today’s prevailing view is that modern humans began migrating en masse from Africa 100,000 years ago, probably through the Arabian Peninsula, the Levant, or both.

They were brought across Europe and along the southern coast of Eurasia, and it is very likely that

have found high quality food sources. Then they went and populated Central Asia, where China today lies. About 65,000 years ago, some people arrived in Sahul, an ancient continent now home to Australia and New Guinea, almost certainly by ship. The last famous migration took humanity beyond the Bering Strait to America about 15,000 years ago.

But what happened to other human species?

According to the standard ‘outside Africa’ model, when our species first spread across Eurasia, they were completely replaced by the more archaic humans they encountered. Undoubtedly, we are the last human species to walk on foot.

But if Homo sapiens was responsible for the extinction of other species, this still remains part of a major debate. What has become clear in recent years is that these meetings were not entirely violent and destructive. At least in some cases, our ancestors made love, not war.

Neanderthals and Denisovans, two of our closest relatives, became extinct tens of thousands of years ago. However, most people around the world have small amounts of DNA inherited from one or both species in their genomes.

This is evidence that Homo sapiens was mated with them, and at least some of these mates produced fertile offspring. Some people in the Middle East still carry the ‘ghost’ DNA today from another species called ‘hominin X’, whose fossils have not yet been found.

Our ancestors may have encountered other hominins as they spread around the world, including the enigmatic ‘hobbit’, Homo floresiensis, which lived on the Indonesian island of Flores until about 50,000 years ago. Last year, it was discovered that a similar species lived at the same time 3,000 miles [3,000 km] south of the Philippine island of Luzon.

However, there is no genetic evidence of mating with any of these species, and the role of Homo sapiens in eradicating them, if any, remains unknown. It was once assumed that the mating between early humans and other hominins took place exclusively outside Africa.

A small amount of Neanderthal DNA has been found in the genomes of people living in Africa, but since Neanderthals do not seem to have ever lived on that continent, it has certainly arrived there as a result of early humans migrating again. in Africa from Eurasia.

However, the latest analysis suggests that there has been a pairing with other hominins on the continent.

In fact, the genomes of some people in Africa are 19 percent “ancient,” a rate that significantly exceeds any contribution of Neanderthals or Denisovans to Eurasian genomes. The first evidence of this pairing was found in 2012, when a team led by Sarah Tishkof of the University of Pennsylvania in the US, discovered ancient DNA in the genomes of modern hunter-gatherer hunters living in Cameroon and Tanzania.

It showed that no more than 30,000 years ago, their ancestors had mated with an unidentified hominin species. Then, in 2018, Arun Durvasula of the University of California, Los Angeles, scanned all human genomes from 4 sub-Saharan populations, and found evidence of an early mating with another unknown archaic hominin.

It appears to have split from our line of descent about 625,000 years ago, and then mated again with humans until 124,000 years ago. This happened before the mass exodus outside Africa, which explains why European genomes carry the same unknown DNA.

Earlier this year, analysis of 4 fossil skeletons from Cameroon found traces of other unidentified DNA from a encounter that occurred about 250,000 years ago. But who could these mysterious relatives of modern man be?

One of the candidates is Homo naledi, a primitive-looking hominin that was discovered in South Africa in 2013, and who lived up to 250,000 years ago. Another is the ancestor of Homo sapiens, who lived about 900,000 years ago, and is now thought to be our direct ancestor.

And this despite the fact that we have no evidence that he lived in Africa. A more likely scenario is that fossils of unknown species have not yet been discovered, and this may never happen. Moreover, there is little doubt that new studies will reveal in our DNA other ancestral ‘ghosts’ ./ NS – Bota.al

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