Nobody knows who it was, just that it was different: A teenage girl over 50.000 years ago appeared to be a "hybrid" ancestor of modern humans that scientists had never seen before. Only recently, researchers have uncovered evidence that she wasn't alone.
In a 2019 study analyzing the tangled mess of mankind's prehistory, scientists have identified a species of "unknown human ancestor" that modern humans encountered during the long journey out of Africa, some 80.000 years does.
Away from Africa: Migrations and Mixing
"When the so-called Out of Africa occurred, part of the human population, already made up of modern humans, abandoned the African continent and migrated, giving rise to all current populations", explains the biologist Jaume Bertranpetit of the Pompeu Fabra University in Spain.
During this journey, human beings have met (in all senses, including sexual) other ancient (and subsequently extinct) hominids.
Until recently, these "casual sexual partners" were thought to include Neanderthals and Denisovans (the latter unknown until 2010). In the most recent study I'm talking about, published in Nature (I link it here) scientists have isolated a third "ex" in Eurasian DNA. A still unknown ancestor.
A new ancestor in the human genome
Using a statistical technique called Bayesian inference, researchers have found evidence of what they call a "third introgression." An archaic "ghost" population that modern humans interbred with during the African exodus.
It is possible that this third population in the "sexual history of mankind" was possibly a mix of Neanderthals and Denisovans. Or that it was something else. “We looked for these points of high divergence in the genome, to see which ones are Neanderthals and which ones are Denisovans, and to see if they explain the whole picture,” says Bertranpetit.
"If you subtract the Neanderthal and Denisovan parts, there is still something left in the genome that is very divergent."
What else will come out?
Discoveries made in this area of science will come ever more rapidly as research is integrated with new methods led by the deep learning. Applying this type of AI analysis is a very new technique, especially in this field.
Gradually, they will help us reconstruct in as much detail as possible the path that the great human family (and hominids) took to get us to what we are now.
