A fossilized human lower jaw found in Taiwan is now considered to be from a Denisovan, an early human relative. Experts propose that this mandible, among the few remains recognized so far, comes from a enigmatic ancestral species that emerged approximately 370,000 years ago.
Scientists currently think they have solved the puzzle of an ancient fossil jaw discovered in Taiwan, recognizing it as belonging to a Denisovan.
Scientists suggest that at some stage, three distinct groups of ancient humans—the Denisovans, Neanderthals, and Homo sapiens, with the last being our direct forebears—lived alongside each other in Eurasia and sometimes intermingled.
Takumi Tsutaya, a biological anthropologist affiliated with the Graduate University for Advanced Studies in Hayama, Japan, who also co-authored the study, clarifies, The Denisovan lineage branched off from the Neanderthal line more than 400,000 years ago. Subsequently, modern humans emerged from African ancestors and moved into Eurasia.
Even with minimal information available on Denisovans, primarily identified through scant fossil records, this specific mandible holds considerable intrigue for researchers.
On the other hand, Neanderthals are more comprehensively documented, with museums such as the Natural History Museum in London and the Museum of the Krapina Neanderthals in Croatia offering extensive exhibits on early human existence.
The Denisovan fossil was first found when a fishing activity scooped up sediment from the seabed of the Penghu Channel, which lies close to 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 research indicates that the jawbone might range from 10,000 to 70,000 years old or potentially from 130,000 to 190,000 years old.
Because of the state of the fossil, conducting an ancient DNA analysis was not possible.
Nevertheless, recent endeavors by researchers in Taiwan, Japan, and Denmark managed to retrieve certain protein sequences from the incomplete 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.
At present, the sole confirmed Denisovan fossils comprise pieces of mandibles, several molars, and a segment of a digit bone discovered within caverns in Siberia and Tibet.
Certain researchers believe that the fossils found in a cave in Laos could potentially be part of this same group.
Denisovans are mainly defined through their genetic information since their physical appearance remains unclear because of the scarcity of well-preserved fossils.
Hence, we depend on genetic analysis for identification. In this case, we could not obtain ancient DNA, probably because of its deterioration.
Rather than doing otherwise, we performed protein analysis and sequenced approximately 4,000 amino acid residues, pinpointing a Denisovan-specific variant.
This variation has not been discovered in modern humans or Neanderthals sequenced so far, yet it exists within the Denisovan genome, according to Tsutaya.
Although the results are promising, certain researchers are holding off on final classification of the Taiwan fossil as Denisovan until more evidence comes to light.
Rick Potts, the director of the Smithsonian Institution’s Human Origins Project—who was not involved in this research—praised the study. However, he pointed out that among the five protein sequences retrieved, just one closely matches those found in known Denisovan remains, whereas the rest might be linked to various other ancient human species.