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An article published in 2013 on SciNews hinted at a third lineage of humans, in addition to Denisovans and Neanderthals, that our ancestors interbred with and whose genetic footprint remains in our genome.
The growing availability of sequenced genomes is allowing scientists to play paleontologists, that is modern ones, not looking at fossils to retrieve the past but looking at the information recorded in the genome. By comparing different genomes it is possible to single out ancestry and correlate with geographical location and migrations that happened tens of thousands of years ago. It has been found out that our ancestors living in South East Asia and Oceania interbred with Denisovans and traces of Denisovans genes, up to 6%!, are still found in today’s homo sapiens living in those areas (that is having ancestry in those areas). Likewise, humans in Europe interbred with Neanderthals -with whom we shared the planet till 40,000 years ago, and up to 2% of Neanderthals genes can be found in humans with a European ancestry.
The article published in 2013 hinted at the existence of other lineages of humans, in addition to our, that still has a record in our present genome.
Now scientists using artificial intelligence algorithms have been able to identify a third lineage (fourth if you include us). The article has been published in Nature Communications on January 19th with the cryptic (for us normal readers) title: “Approximate Bayesian computation with deep learning supports a third archaic introgression in Asia and Oceania”.
The findings are the result of a joint work by a team or researchers in Barcelona (Spain) and Tartu (Estonia) who applied artificial intelligence to the analyses of differences in genomes. The analyses confirmed the contamination (introgression) of Denisovans and Neanderthals present in our genome plus identified a third one that was either directly interbreeding with our ancestors or that bred with Denisovans and Neanderthals. In this latter case our genome acquired this third lineage genes via the interbreeding with Denisovans and Neanderthal.
It is interesting to notice that all human beings living today show a single common forefather going back to some 300,000 years ago, a forefather with an African root. The migration from Africa can be followed by looking at the genomes of people living today and as we trace those migration we trace also the interbreeding that took place with other lineages of humans. Although there have been several migrations out of Africa there is consensus that current humans can be traced back to a migration that took place some 100,000 years ago (relatively recent, if you compare this to life on our planet, 3.5 billion years) and at that time several lineages of humans existed and interbred.
I am amazed of the possibility of reading our genetic history, pinpointing events that occurred tens of thousands years ago. The notion that we have an history book engraved in each our our cells is astonishing, and even more astonishing that we are asking computers to read that book for us.
