This 7,000-year-old mummy DNA has revealed a ‘ghost’ branch of humanity

Today, the Sahara Desert is one of the most inhospitable places on our planet. But it wasn’t always this way. 

Roll the clock back 7,000 years, and the Sahara was a lush, green savannah, teeming with wildlife, dotted with lakes – including one the size of modern-day Germany. It was, in other words, the perfect place for our ancient ancestors to settle.

But who were they? We might finally know.

Scientists have successfully analysed the DNA of two naturally mummified individuals from the Takarkori rock shelter, in what is now southwestern Libya. Their findings reveal something extraordinary: these ancient people belonged to a previously unknown branch of the human family tree.

The two women belonged to a so-called ‘ghost population’ – one that had only ever been glimpsed as faint genetic echoes in modern humans, but never found in the flesh.

“These samples come from some of the oldest mummies in the world,” Prof Johannes Krause, senior author of the new study, told BBC Science Focus. It is, he explained, remarkable that genome sequencing was possible at all, given hot conditions tend to degrade such information. 

Genome sequencing is the process of reading the complete set of genetic instructions found in an organism’s DNA – a kind of biological blueprint.

Earlier studies had examined the mummies’ mitochondrial DNA, which is much more limited. It’s passed down only through the maternal line, and is far shorter than the full genome found in the cell nucleus.

“There are around 16,000 base pairs in mitochondrial DNA,” Krause said. “That might sound like a lot, but compared to the whole genome, which has 3.2 billion, it’s just a fraction.”

So what did the team discover from this newly unlocked genetic treasure trove?

First, they found that this lost lineage split from the ancestors of sub-Saharan Africans around 50,000 years ago – about the same time other groups were beginning to migrate out of Africa. 

Remarkably, this group then remained genetically isolated from other groups of humans for tens of thousands of years, all the way through to the time when these two women died around 7,000 years ago. 

“It’s incredible,” Krause said. “At the time when they were alive, these people were almost like living fossils – like something that shouldn’t be there. If you’d told me these genomes were 40,000 years old, I would have believed it.” 

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