New evidence in search of the mysterious Denisovans

An international group of researchers led by the University of Adelaide conducted a comprehensive genetic analysis and found no evidence of the cross between modern humans and the ancient humans known from fossil records in Southeast Asia. They did find further DNA evidence of our mysterious ancient cousin, Denisovans, which may mean that there are great discoveries in the region.

In the study published in Natural ecology and evolution , the researchers examined the genomes of more than 400 modern humans to investigate the cross-events between ancient humans and modern human populations that arrived on the island of Southeast Asia 50,000–60,000 years ago.

They particularly focused on tracing signatures indicating that they cross from deeply diverse species known from the area’s fossil record.

The region contains one of the richest fossil recordings (from at least 1.6 million years) documenting the evolution of humans in the world. Currently, there are three different ancient humans recognized from the fossil record in the area: Homo erectus, Homo floresiensis (known as Flores Island hobbits) and Homo luzonensis.

These species are known to have survived until about 50,000 to 60,000 years ago in the cases of Homo floresiensis and Homo luzonensis, and about 108,000 years for Homo erectus, which means that they may have overlapped with the advent of modern human populations. .

The results of the study showed no evidence of breeding. Nevertheless, the team was able to confirm previous results showing high levels of Denisovan descent in the region.

Principal Author and ARC Research Associate of the University of Adelaide, Dr. João Teixeira, said: “Unlike our other cousins, the Neanderthals, who have an extensive fossil record in Europe, the Denisovane is known almost exclusively from the DNA record. The only physical evidence of the existence of Denisovan was a finger bone and other fragments found in a cave in Siberia, and more recently a piece of jaw found on the Tibetan plateau. ‘

‘We know from our own genetic records that the Denisovans mingled with modern humans who came from Africa 50,000–60,000 years ago, both in Asia and while modern humans moved through the island of Southeast Asia on their way to Australia. .

‘The levels of Denisovan DNA in today’s populations indicate that significant cross-breeding took place on the island of Southeast Asia.

“The mystery then remains, why did we not find their fossils next to the other ancient people in the region? Should we re-examine the existing fossil record to consider other possibilities?” says Dr. João Teixeira.

Co-author Chris Stringer of the Natural History Museum in London added: “Although the famous fossils of Homo erectus, Homo floresiensis and Homo luzonensis seem to be in the right place and time to represent the mysterious ‘southern Denisovans’, their ancestors were ‘Probably was on the island of Southeast Asia at least 700,000 years ago. This means that their lineages are too old to represent the Denisovans, who from their DNA were more closely related to the Neanderthals and modern humans.’

Co-author Prof Kris Helgen, lead scientist and director of the Australian Museum Research Institute, said: ‘These analyzes provide an important window for human evolution in a fascinating region and demonstrate the need for more archaeological research in the region between the mainland Asia and Australia. ‘

Helgen added: “This research also illuminates a pattern of ‘megafaunale’ survival that coincides with known areas of pre-modern human occupation in this part of the world. Large animals that survive in the region today include the Komodo. dragon, the Babirusa (a pig with remarkable inverted fangs), and the Tamaraw and Anoas (small wild buffalo).

“This suggests that prolonged exposure to hunting pressure by ancient humans could have facilitated the survival of the megafaunal species in subsequent contact with modern humans. Areas without documented pre-modern human appearance, such as Australia and New Guinea, have completely destroyed the country. extinct. animals that have been larger than humans for the past 50,000 years. ‘

Dr Teixeira said: “The research confirms previous studies that the Denisovans were in the island of Southeast Asia, and that modern humans did not cross with more diverse human groups in the region. This offers two equally exciting possibilities: a great discovery is in that way, or we have to reevaluate the current fossil record of Southeast Asia Island. ‘

“No matter how you look at it, exciting times lie ahead in paleontropology.”