New clues about the most mysterious human ancestor

BarcelonaThe puzzle of the enigmatic lineage of the Denisovans, an extinct group of hominids that coexisted with Neanderthals over time – they were even related and are considered distant cousins due to their genetic differences – and that has left its mark on the genome of modern humans. The last identified piece of this ancestor is a Pleistocene male jaw fossil that a fisherman rescued from the seabed in what is now Penghu Channel, on the island of Taiwan, 17 years ago. This discovery shows that the Denisovan It managed to survive in the cold mountains of Siberia and Tibet, but also in warm and humid latitudes of East Asia. The study, published in the journal Science, also allows us to delve deeper into the characteristics that these archaic ancestors shared and that differentiate them from Neanderthals.

The story of this fossil is extraordinary for several reasons. To begin with, the way it was found. In 2008, a fisherman who had set out with his nets 25 km off the western coast of Taiwan—an area that was part of the continent during the Pleistocene, when sea levels were lower—made this surprising catch at a depth of a hundred meters and sold it to an antique dealer. Later, a citizen acquired it and gave it to the National Museum of Natural Science in Taiwan, where researchers realized that it was necessary to delve deeper into its morphology and genetic material to identify which evolutionary line it belonged to. In fact, it wasn't until 2019 that people began to suspect that it could belong to the Denisovan group, but rather a new lineage or subspecies ofHomo erectus specific to Asia.

Now, led by physical anthropologist Takumi Tsutaya, a team of researchers from Sokendai Graduate University for Advanced Studies in Japan and the University of Copenhagen have conducted a paleoproteomic analysis of the fossil lower jaw and have concluded that it dates back 0, 00 to 130,000 and 190,000 years. This discipline studies proteins in fossil material to reconstruct amino acids (the "pieces" of proteins) and, unlike paleogenomics, which studies ancient DNA, it allows molecules to be identified further back in time, since the samples are more stable, less fragile and therefore better preserved.

The anthropologists extracted proteins from the bone and tooth enamel of the fossil and recovered more than 4,200 amino acid residues, among which they found two specific Denisovan variants. According to the research, these variants are rare among modern humans, but are more common in regions where there was hybridization with this hominid, which survived for hundreds of thousands of years before becoming extinct.

Very peculiar teeth

The team also found a jaw structure shared with those observed in the confirmed Tibetan Denisovan specimen: the body is thick and low, with large molars and robust, distinctive root structures. "This suggests that these features were characteristic of the lineage and perhaps male-specific," the study's authors explain. But why is this important? According to the researchers, this shows that in Eurasia, during the middle and late Pleistocene, "two groups of hominins coexisted," since, unlike Denisovans, Neanderthals had small teeth with high jaws.

The mysterious subspecies remained completely unknown until 2010, when a fragment of a small finger bone was found in Siberia's Denisovan Cave, the hiding place that eventually gave the group its name. Inside this cave, genetic material dating back 200,000 years was extracted from a few fossil remains and genetic clues in the ground to identify the existence of this hominid. The first first-generation hybrid between a Neanderthal and a Denisovan was also identified there.

However, until now, direct evidence of Denisovans has only been found outside of Siberia on the Tibetan Plateau: a jawbone and a rib dating back 160,000 years, that is, before theHomo sapiens migres from Africa. A tooth attributed to a girl was also identified in a cave in Laos, although its molecular origin has not been confirmed, as have other fossils in China. Thus, the discovery by Tsutaya and his colleagues demonstrates the "wide" geographic distribution of a group that the scientific community has long said was extraordinarily versatile in adapting to different climates and terrain.