Scientists discovered evidence that pointed to a previously unknown ancestor of humans after rinsing the human genome using artificial intelligence.
According to a paper published in nature Communications by a team of researchers in Spain and Estonia, the human ancestor existed about 80,000 years ago. This new evidence could help explain the genetic links between modern humans and our ancestral cousins, Denisovan and Neanderthals.
An abundance of evidence suggests that early Homo sapiens interfered with Neanderthals, who left Africa more than 200,000 years earlier than Homo sapiens did. Denisovans was only added to the human genus in 2008 after the discovery of a pinkie bone and tooth in a Siberian hole, but genetic analysis has shown that interbreeding also occurred between Homo sapiens and Denisovans.
But the study's author's note, Homo sapien's breeding with these other two hominid species alone, could not account for all the inexplicable genetic residues of the modern human genome. A third human ancestral interbreeding with old people seemed likely, but until recently there was no evidence to support the existence of a third ancestor in the mix.
Last summer, a research group found a bone fragment in Russia that belonged to a child who was perceived by a neanderthal and denisovan father. This remarkable conclusion suggested that not only Homo sapien's interbreeding with Neanderthals and Denisovans, but these two species were also interbreeding with each other.
Read more: A Hybrid of Humanity's closest relatives has been identified in 50,000-year-old Bone
This discovery seemed to point to the hypothetical lack of third nature that could account for the inexplicable parts of the modern human genome. The obstacle genetics are faced with mapping not only Neanderthal and Denisovan interbreeding, but also interbreeding between Homo sapiens and a Neanderthal-Denisovan hybrid.
According to a statement by the Barcelona Center for Genomic Regulation, one of the three institutions involved in the research was "mapping these demographics" "much more complex than anything else considered so far" for human development analysis .
The usual statistical tools used by geneticists would simply not cut it and so the researchers turned to deep learning.
Deep learning is a type of machine learning that uses a network architecture that is loosely modeled on the human brain to analyze massive amounts of information into complex patterns. Working backwards with deep learning, the researchers fed the network various demographic models of ancient populations that contained this Neanderthal-Denisovan hybrid until it produced a genome that matched the modern human genome.
This showed that the disappeared ancestor of humans might well be the by-product of Neanderthal-Denisovan interbreeding.
"When we run a simulation, we travel along a possible path in the history of humanity," said Oscar Lao, a population geneticist at the Center for Genomic Regulation and a co-researcher. "Of all the simulations, deep learning allows us to observe what makes the ancestral puzzle fit."
Scientists still need more evidence for the final joining of our ancient history. Mayukh Mondal, an evolutionary biologist at the University of Tartu and a co-author of the study, acknowledged in a statement that "we cannot yet exclude other opportunities".