New study shows 'ghost DNA' in people from modern-day west Africa

Evidence grows that ancient humans mixed with unknown race of people as new study shows ‘ghost DNA’ in samples from modern-day population of west Africa

  • The researchers studied the genetic material of 405 people from West Africa 
  • They discovered mystery genetic material, which they have termed ‘ghost DNA’
  • It suggests that humans mixed with an unknown group about 50,000 years ago 

Researchers have found ‘ghost DNA’ in hundreds of people from modern-day West Africa, suggesting ancient humans mixed with a previously unknown group about 50,000 years ago. 

The stunning find, published in the journal Science Advances, came after the scientists analysed genetic material from 405 people from Nigeria and Sierra Leone. 

They discovered signals of what they have termed ‘ghost DNA’, which they believe comes from a group of humans that were previously unknown. 

Although there are no bones or DNA to prove the theory, the researches say the evidence is clear in the genes of modern day West Africans. 

Study authors Sriram Sankararaman and Arun Durvasula 

It is not the first time ‘ghost DNA’ has been identified in the genes of Africans. 

In Cameroon in January, DNA discovered in four skeletons that belonged to children buried at a rock shelter at an archaeological site called Shum Laka also point to the existence of a long-lost ‘ghost’ branch of the human family tree.

All four skeletons inherited about one-third of their DNA from ancestors similar to the hunter-gatherers of western Central Africa.

The remaining two thirds of their DNA, however, came from an ancient West African source, including a ‘long lost ghost population’ previously unknown to science.  

This, coupled with the most recent discovery, further cimplicates the picture of how modern humans evolved from other, related races. 

Sriram Sankararaman, a computational biologist at UCLA and one of the study’s authors, said: ‘It’s almost certainly the case that the story is incredibly complex and complicated and we have kind of these initial hints about the complexity.’

It is thought that the interbreeding occurred roughly 50,000 years ago, around the same time that Neanderthals were breeding with modern humans elsewhere in the world (stock photo)

He admitted that the mystery DNA didn’t belong to Neanderthals or other known groups, such as Denisovans, and said that he and his co-author Arun Durvasula believe it is from a new group entirely. 

Sankaraman added: ‘We don’t have a clear identity for this archaic group.

‘That’s why we use the term ‘ghost.’ It doesn’t seem to be particularly closely related to the groups from which we have genome sequences from.’ 

In their research, they analysed the genomes of the West Africans and used a statistical model to identify different parts of the DNA. 

They explained the technique ‘pulls out chunks of DNA which we think are likely to have come from a population that is not modern human.’

It is thought that the interbreeding occurred roughly 50,000 years ago, around the same time that Neanderthals were breeding with modern humans elsewhere in the world.  

Sharon Browning, a biostatistics professor at the University of Washington who has studied the mixing of Denisovans and humans told NPR: ‘The scenario that they are discovering here is one that seems realistic.’

Browning adds the ghost DNA appears frequently in the genetic material which suggests that it is ‘useful’ to modern humans. 

However, the study authors admit its unknown what role the ghost genes play in humans who carry them.   

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