New research studying human DNA has found that more than 30,000 years ago, the first humans bred with mysterious ‘alien species’.
According to scientists, restructured genome sequences from two relatives of modern man show that these groups reproduced with several hominid species, one of which was “not human”.
These ancient genomes, one from a Neanderthal and one from a Denisovan, were presented at a meeting on ancient DNA at the Royal Society in London.
The results reveal that interbreeding occurred between members of several ancient hominid groups in Europe and Asia over 30,000 years ago, including an unknown human ancestor from Asia.
As explained by Mark Thomas, an evolutionary geneticist at University College London who attended the meeting but wasn’t involved in the research, “What it begins to suggest is that we’re looking at a Lord of the Rings-type world — that there were many hominid populations.”
The first published genomes from Neanderthals and Denisovans have revolutionized the study of ancient human history because they confirmed that these groups interbred with anatomically modern humans thus contributing to the genetic diversity of humans today.
All modern humans whose ancestors derive from Africa owe 2% of their genomes to Neanderthals. Some Oceania populations, including the people of Papua New Guinea and the Australian Aborigines, share 4% of their DNA with the Denisovans, members of a group named after in the Altai Mountains in Siberia, Russia, where they were discovered. The cave contains remains deposited between 30,000 and 50,000 years ago.
David Reich, an evolutionary geneticist at Harvard Medical School in Boston, Massachusetts took part in studies. At the meeting, however, he stated that the conclusions were based on low-quality genome sequences, full of gaps and errors.
Together with collaborator Svante Pääbo at the Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany, his team has now produced a much more complete version of the Neanderthal and Denisovan genome, which matches the quality of modern human genomes. These high-quality Neanderthal and Denisovan genome sequences are based on bones from the Denisova Cave.
Reich also stated at the meeting that along with the interbreeding with the Oceanian ancestors, Denisovans also reproduced with Neanderthals and the ancestors of modern humans in China and other parts of East Asia.
According to him, “Most surprisingly, the genomes indicate that Denisovans interbred with yet another extinct population of archaic humans that lived in Asia more than 30,000 years ago — one that is neither human nor Neanderthal.”
A lot of theories were put forward at the meeting regarding the identity of this unknown human population.
“We don’t have the faintest idea,” explained Chris Stringer, a paleoanthropologist at the Natural History Museum in London, who didn’t take part in the research. According to him, the population is possibly related to Homo heidelbergensis, a species that left Africa around half a million years ago and later gave rise to Neanderthals in Europe. “Perhaps it lived on in Asia as well,” said Stringer.