Today, the Sahara desert is one of the least popular places on our planet. But that wasn’t always the case.
Returning the clock to 7,000 years, the Sahara is a lush green savanna filled with wildlife and dotted with lakes containing one of the sizes of modern Germany. In other words, it was the perfect place for our ancient ancestors to settle down.
But who were they? We may finally know.
Scientists analyzed the DNA of two naturally occurring mummy individuals from a shelter in Takalkori rock in what is now southwestern Libya. Their discoveries reveal something extraordinary. These ancient people belonged to previously unknown branches of human family trees.
The two women belonged to the so-called “ghost population.” This is something that modern humans have only seen glimpses of as faint genetic echoes, but they have not been seen in the body.
“These samples come from some of the oldest mummies in the world.” Professor Johannes Krause senior author of the new study said BBC Science Focus. He explained that it is surprising that genomic sequencing is absolutely possible because high-temperature conditions tend to decompose such information.
Genomic sequencing is the process of reading a complete set of genetic instructions found in the DNA of an organism, a type of biological blueprint.
Previous studies have examined mitochondrial DNA in mummies, which is much more limited. It is passed only through the maternal line and is much shorter than the complete genome found in the cell nucleus.
“There are about 16,000 base pairs in mitochondrial DNA,” Klaus said. “It may sound a lot, but compared to the entire 3.2 billion genome, it’s just a small portion.”
So what have the team discovered from this new, unlocked genetic treasure trove?
First, they discovered that this lost lineage had split from sub-Saharan African ancestors about 50,000 years ago.
Surprisingly, this group remained genetically isolated from other human groups for tens of thousands of years.
“It’s incredible,” Klaus said. “When they were alive, these people were like most fossils, like things they shouldn’t be there. If I had said these genomes were 40,000 years old, I would have believed it.”
This long-term quarantine reveals two key insights. First, the “Green Sahara,” which continued 15,000 to 5,000 years ago, was a lush human habitat, but as many scientists had previously envisioned, it was not useful as a moving corridor between the north and sub-Saharan Africa.
Second, there was genetic mixing with northern populations, including Neanderthals. But it was limited – much less than the non-African population, carrying about 10 times more Neanderthal DNA than the Takalkori people.
We know that these people were idyllics and meant that they kept livestock like cows. But they
Genetic segregation suggests that this lifestyle was adopted by exchanging knowledge and practice with neighbouring groups rather than moving or subsequent genetic mixing. Again, this is a surprise to scientists.
Unsolved puzzles
The whole mummy genome sequence revealed much about this lost human lineage. Still, there are many more mysteries left.
“The Sahara greening only happened 15,000 years ago. Before that, it was once again desert,” Klaus said. “So we don’t really know where they were strolling around 50,000 years ago, when they split from the population of Africa’s southern Africa, and 15,000 years ago.”
Wherever they went, they must have remained isolated for tens of thousands of years. Perhaps the lost Eden? We may never know.
“That’s a real mystery,” Klaus added.
Krause’s research was published in Nature.
About our experts
Johannes Kraus is the director of the Max Planck Institute of Evolutionary Anthropology at the Ministry of Archaeology’s Institute of Evolutionary Anthropology in Leipzig, Germany. He is also a professor of archaeology at the Institute of Zoology and Evolution at Jena, University of Friedrich Schiller, Germany. Krause is a predominantly peer-reviewed journal, with over 250 publications. Nature, Science, Cells, Nature reviews genetics. In 2010 he was awarded the AAAS Newcomb Cleveland Award and the 2017 Thuringian Research Award for Top Performance in Basic Research.
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Source: www.sciencefocus.com