Muhamad Yehia .. Cairo
A fossilized human jawbone discovered in Taiwan is now thought to belong to a Denisovan, an ancient human relative. Researchers suggest that this mandible, one of the rare specimens identified to date, originated from a mysterious human ancestor believed to have appeared around 370,000 years ago.
Scientists now believe they have unraveled the mystery surrounding an ancient fossil jawbone found in Taiwan, identifying it as Denisovan.
Researchers indicate that at one point, three groups of human ancestors—Denisovans, Neanderthals, and Homo sapiens, the latter being our direct ancestors—coexisted in Eurasia and occasionally interbred.
Takumi Tsutaya, a biological anthropologist from the Graduate University for Advanced Studies in Hayama, Japan, and a co-author of the study, explains, “Denisovans are closely related to Neanderthals, having diverged over 400,000 years ago. Following this split, Homo sapiens evolved from African hominins and migrated to Eurasia.”
Despite the limited knowledge about Denisovans, who are known from very few fossil remains, this particular jawbone is of significant interest to scientists.
In contrast, Neanderthals are better understood, with institutions like the Natural History Museum in London and the Museum of the Krapina Neanderthals in Croatia showcasing detailed representations of early human life.
The Denisovan fossil was initially discovered during a fishing operation that dredged the seabed in the Penghu Channel, located near the Taiwan Strait.
After being sold to an antique shop in Tainan City, a collector recognized its significance, purchased it in 2008, and later donated it to Taiwan’s National Museum of Natural Science.
Marine invertebrates found attached to the fossil allowed researchers to date it to the Pleistocene era, but the specific species of early human ancestor remained uncertain.
The study suggests that the mandible could be between 10,000 to 70,000 years old or possibly 130,000 to 190,000 years old.
Due to the fossil’s condition, ancient DNA analysis was not feasible.
However, recent efforts by scientists in Taiwan, Japan, and Denmark successfully extracted some protein sequences from the partial jawbone.
The researchers concentrated on several existing protein sequences that they claim are similar to those found in the genome of a Denisovan fossil discovered in Siberia.
Tsutaya explains, “We have limited knowledge about the physical characteristics of Denisovans, but we do possess the genomic sequence of a single Denisovan individual. This allows us to analyze their genetic connections with modern humans and Neanderthals.”
A map shared by Tsutaya highlights the locations of sites where fossils identified as Denisovan or believed to be Denisovan have been molecularly confirmed.
The accompanying images depict the coastline of Penghu, Taiwan, near the site of the fossil discovery.
Researchers emphasize that each new find is significant, given the limited information available about Denisovans.
Currently, the only verified Denisovan fossils consist of fragments of jawbones, a few teeth, and a section of a finger bone unearthed in caves located in Siberia and Tibet.
Some scientists speculate that fossils discovered in a cave in Laos might also belong to this group.
“Denisovans are primarily characterized by their genetic data, as their physical form remains largely unknown due to the lack of informative fossils.
Therefore, we rely on genetic analysis for identification. In this instance, we were unable to extract ancient DNA, likely due to its degradation.
Instead, we conducted protein analysis and sequenced around 4,000 amino acid residues, identifying a Denisovan-specific variant.
This variant is not found in the modern humans and Neanderthals sequenced to date, but it is present in the Denisovan genome,” Tsutaya states.
While the findings are encouraging, some scientists are awaiting additional evidence before definitively classifying the Taiwan fossil as Denisovan.
Rick Potts, director of the Smithsonian Institution’s Human Origins Project, who did not participate in the research, commended the study but noted that out of the five protein sequences recovered, only one strongly aligns with previously identified Denisovan fossils, while the others could potentially relate to different hominin groups.