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The research on Denisovan's story is always fascinating. This group of ancient hominines has been a mystery since their discovery in 2010 as a missing sister group of Neanderthals. Pieces of their story unfold slowly and almost everything is a surprise. Take for example the new research on the first example of Denisovan remains found outside their famous Siberian cave; The location shocked the researchers for several reasons.
First, although Denisovan's DNA has been identified in Asian, Australian and Melanesian populations, Science Daily points out that this is the first time researchers have identified the physical remains of a Denisovan outdoors of the cave, which gave it its name, Denisova Cave, in Siberia.
The spread and evolution of Denisovans based on evidence available in 2014. (John D. Croft / CC BY SA 3.0 )
Secondly, the Denisovan mandible fragment was found on the current Tibetan Plateau of Xiahe, China, at an elevation of over 2,838 feet (2438.40 meters) above the cave where all the others remains of Denisovan have been discovered. This has raised questions about when adaptive genes for living in low oxygen environments have emerged in the region.
The Xiahe jaw
According to National Geographic, an anonymous monk discovered the prehistoric fragment of the jaw into hominin in Xiahe's Baishiya Karst Cave in 1980. He donated it to Gung-Thang's 6th Living Buddha who later gave it to the University. from Lanzhou. The jaw had remained in the university collection for over 30 years, before study co-author, Dongju Zhang of Lanzhou University, decided that the hominin mandible was worth the look in 2016.
Baishiya Karst Cave in Xiahe, China. ( Dongju Zhang, Lanzhou University )
And she was lucky. A first examination of the morphology of the mandible showed that it did not have the elongated teeth of Homo erectus or the chin of Homo sapiens – both groups with a large amount of remains throughout mainland Asia. But the size of the teeth suggested something that at first glance might seem a little suspicious: teeth similar to the examples found in Denisova's cavern with Denisovan's DNA.
A heavy carbonate crust was attached to the mandible and a serial U dating revealed to researchers that the jaw was at least 160,000 years old. Another fascinating discovery, because Chuan-Chou Shen of the Department of Geosciences of the National Taiwan University, who directed the dating, states that "this minimum age is equal to that of the oldest specimens of the cave Denisova".
The proof is in the protein?
The researchers did not find any DNA preserved in the fossil so they had to find an alternative method to determine if the remains were actually Denisovan. Frido Welker, MPI-EVA and the University of Copenhagen, explained that an old protein analysis on protein extracted from one of the molars showed that "the Xiahe mandible belonged to a population of hominins closely related to the Denisovans of the cave of Denisova ".
The Xiahe mandible, represented only by its right half, was found in 1980 in the cave Baishiya Karst. ( Dongju Zhang, Lanzhou University )
One of the problems of protein analysis is the depth at which it is possible to determine which group of Denisovan the individual belonged to, or whether he may have been in another hominin group. Earlier this year, Andrew Collins explained that "there may have been three different types of Denisovans at the same time".
The excavators went to Baishiya Karst cave to see what other secrets it might contain. But to date, researchers have found only large animal bones with cutting marks and stone tools. They can not be sure if the Denisovans manipulated these artifacts. No other potential Denisovan vestige has been identified.
Excavations in the cave Baishiya Karst. ( Dongju Zhang, Lanzhou University )
Adapt and spread genes
Denisova Cave has an elevation of 699.82 meters and the Baishiya Karst Cave where the mandible fragment was found is at an altitude of 3279.95 meters. According to a press release from the Max Planck Institute, it is the oldest fossil of hominin discovered so far on the Tibetan plateau, which means that the locals 'inhabitants' Were already adapted to life in this high-altitude, low-oxygen environment. " even before Homo sapiens arrives in the area. "
However, as National Geographic notes, "Even if the jaw has been found where oxygen levels are low, without the DNA itself, scientists can not be sure that the jaw owner has done the same. adaptation necessary to survive in this small air ".
What other questions does this discovery of Denisovan raise?
The Denisovans themselves were only identified as a distinct hominin group in 2010 when a research team sequenced the genome of a fossil finger discovered in Denisova Cave in Russia and was shown that he belonged to a genetically distinct hominin group of Neanderthals.
The results of this study encourage other researchers working in high altitude caves in Asia to question the remains they have discovered or may find in the future. Discoveries that we thought were Neandertal remains could be Denisovan … or another unknown old hominin. The prehistoric family tree of hominins is expanding and diversifying!
Top image: Baishiya Karst Cave in Xiahe, China. Source: (Dongju Zhang, Lanzhou University ) Insert: The Xiahe mandible, only represented by its right half, was found in 1980 in Baishiya Karst cave. ( Dongju Zhang, Lanzhou University )
By Alicia McDermott
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