Tooth Belonging To Mysterious Human Ancestor Revealed By Experts

What do we know about the Denisovans?

In 2010, it became known that paleogeneticists had read the ancient genome of an individual from Denisova Cave, which turned out to be different from both modern anatomical humans (Homo sapiens) and Neanderthals (H. neanderthalensis).

Scientists made this discovery by examining the nail phalanx of the little finger of Denisov-3, which belonged to a teenager aged 13-16 years, who lived about 76.2-51.6 thousand years ago.

In the 12 years since the publication of this article, scientists have managed to discover less than a dozen fossils that can be reliably considered Denisovan. With the exception of one found in the Tibetan Baishiya Cave, all of them were excavated in the Denisova Cave.

The study of materials from this monument showed that the Denisovans appeared in Altai about 300 thousand years ago and, apparently, disappeared at the beginning of the Upper Paleolithic.

One of the most striking finds made during this time was a small fragment of Denisov-11 bone. DNA analysis showed that it belonged to a girl whose mother was a Neanderthal and her father was a Denisovan.

Although the Denisovans died out a long time ago, they have contributed to many populations of modern humans, such as the indigenous populations of Southeast Asia, Oceania, and Australia.

Denisovan genes

A recent study showed that some tribes of Negritos in the Philippines inherited 34-40 percent more Denisovan genes than indigenous Australians and Papuans, that is, the most in the world. In addition, several studies at once demonstrated that some modern populations received contributions from two different groups of Denisovans.

It seems that these archaic people in ancient times inhabited vast territories from Altai to Southeast Asia. It is possible that some already known ancient finds belonged to this population. So, last year such suspicions fell on a skull from Harbin.

Site stratigraphy and photographs taken during sediment sampling. Credit: Fabrice Demeter et al. / Nature Communications, 2022
Site stratigraphy and photographs taken during sediment sampling. Credit: Fabrice Demeter et al. / Nature Communications, 2022

Archaeologists discovered a tooth of a mysterious human ancestor, possibly Denisovan

An international team of scientists led by Laura Shackelford of the University of Illinois at Urbana-Champaign examined a hominin mandibular molar (TNH2-1).

It was discovered during excavations in the Tam Ngu Hao 2 cave, located in the Annamese Mountains in Laos. The morphology of this tooth demonstrates that it is the first or second lower molar of a child whose age at the current rate of development was about 3.5–8.5 years.

Using uranium-series and electron spin resonance techniques, scientists dated three animal teeth, establishing that the deposits date back to 188,000 to 117,000 years ago. In addition, they carried out optical dating, obtaining two more time intervals: 143±24 and 133±19 thousand years ago.

These dates are consistent with the estimate of the age of the sintered stone (104 ± 27 thousand years ago), which limits the latest time of sediment accumulation. Given these data, the scientists came to the conclusion that the tooth dates back to 164-131 thousand years ago.

Faunal materials from this cave are represented mainly by individual teeth of large mammals. Moreover, most of them were damaged by porcupines, so it was difficult to determine the species identity of these remains due to poor preservation. However, the researchers noted that the fauna of this region was similar to that which existed at the end of the Middle Pleistocene in southern China or northern Indochina.

Morphology of the TNH2-1 tooth, believed to be Denisovan. Credit: Fabrice Demeter et al. / Nature Communications, 2022
Morphology of the TNH2-1 tooth, believed to be Denisovan. Credit: Fabrice Demeter et al. / Nature Communications, 2022

Which species did scientists attribute it to? Is it a Denisovan tooth?

The researchers conducted a proteomic analysis of TNH2-1 tooth enamel but failed to find a single peptide that would reliably attribute these remains to modern anatomical humans, Neanderthals, or Denisovans. However, the protein sequences showed that the sample actually belonged to an individual from the genus Homo, which, apparently, was female.

An analysis of the internal and external structure of the molar showed that this find demonstrates the greatest similarity with the specimen from the Baishiya cave. In absolute size, only the teeth of Middle Pleistocene humans from Asia show larger dental crowns.

In addition, the proportions of the crown tissue coincide with those of the second molar of the jaw from the Baishiya cave, as well as the Denisov-4 upper molar. The complex occlusal surface of a tooth from Laos also distinguished it from Floresian (H. floresiensis), Luzon (H. luzonensis), and anatomically modern humans.

Paleoanthropologists have come to the conclusion that theoretically, this tooth could belong to a Neanderthal. This would have significantly expanded the ecumene of this species of ancient people to the southeast. However, given the similarity to the specimen from the Baishiya cave, they concluded that the molar most likely belonged to a Denisovan.

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The post Tooth Belonging To Mysterious Human Ancestor Revealed By Experts appeared first on Curiosmos.

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