Replica of the Sangiran 17 Homo erectus skull of Java. Credit: Photo provided by the trustees of the Natural History Museum.
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.
An international group of researchers, including experts from the Natural History Museum and led by the University of Adelaide, conducted a comprehensive genetic analysis and found no evidence of interbreeding between modern humans and the ancient humans known from fossil recordings in the Southeast. Asia. The team found further DNA evidence of our mysterious ancient cousins, the 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 people recognized from the fossil record in the area: Homo erectus, Homo floresiensis (known as Flores Island hobbits) and Homo luzonensis.
It is known that these species lived up to about 50,000–60,000 years ago in the cases of Homo floresiensis and Homo luzonensis, and about 108,000 years for Homo erectus, which means that they 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 a high level of Denisovan descent in the region.
A replica of the Homo erectus Sangiran 17 skull found in Java, Indonesia. There are no signs that modern humans with ancient human genera, such as H. erectus, are native to the island of Southeast Asia. Credit: Photo provided by the trustees of the Natural History Museum.
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 Denisovan’s existence was a finger bone and some 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 mixed with modern humans who came from Africa 50,000–60,000 years ago, both in Asia, and that modern humans migrated through the island of Southeast Asia on their way to Australia. . The levels of Denisovan DNA in contemporary populations indicate that significant cross-breeding occurred 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? Do we need to re-examine the existing fossil record to consider other possibilities? ‘
Co-author Prof Chris Stringer of the Natural History Museum added: “While the famous fossils of Homo erectus, Homo floresiensis and Homo luzonensis they seem to be in the right place and time to introduce the mysterious ‘southern Denisovane’, their ancestors were probably 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, chief scientist and director of the Australian Museum Research Institute, said: ‘These analyzes provide an important window for the evolution of people in a fascinating region and demonstrate the need for more archaeological research in the region between the continents. of Asia and Australia. ”
Prof Helgen added: “This research also illuminates a pattern of ‘megafaunal’ survival that coincides with well-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 long-term exposure to hunting pressure by ancient humans could facilitate the survival of the megafaunal species in subsequent contact with modern humans. Areas without documented pre-modern human occurrence, such as Australia and New Guinea, have completely wiped out land animals larger than humans over the past 50,000 years. ”
Dr Teixeira said: “The research corroborates previous studies that the Denisovans were in the island of Southeast Asia, and that modern humans did not breed with more diverse human groups in the region. This offers two equally exciting possibilities: either a great discovery is on its way, or we have to reevaluate the current fossil record of the island of Southeast Asia. ‘
“No matter how you look at it, there are exciting times ahead in paleoanthropology.”
Reference: “Widespread Denisovan Descent in the Island of Southeast Asia, but No Evidence of Substantial Super-Archaic Mixture of Hominins” by João C. Teixeira, Guy S. Jacobs, Chris Stringer, Jonathan Tuke, Georgi Hudjashov, Gludhug A. Purnomo, Herawati Sudoyo, Murray P. Cox, Raymond Tobler, Chris SM Turney, Alan Cooper and Kristofer M. Helgen, 22 March 2021, Natural ecology and evolution.
DOI: 10.1038 / s41559-021-01408-0
Funding: ARC Indigenous Discovery Grant, ARC Laureate Fellowships, Calleva Foundation, Human Origins Research Fund