Denisovans

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Context: Denisovans were living on the Tibetan plateau surprisingly recently, scientists say

Details

• The Denisovans are an extinct relation to modern humans who lived in Siberia and East Asia.

Arguments over interrelation between Neanderthals and even Homo sapiens

• Some experts have argued that Denisovans are an entirely new species of our genus, Homo, but others think that they are merely eastern Neanderthals.
• The fossils indicate they inhabited southern Siberia’s Denisova Cave (hence ‘Denisovans’) 50,000 to 200,000 years ago.
• Denisovan partial mandible discovered in a cave in the Tibetan Plateau indicates that they could be found in the region over 160,000 years ago at least.
• These findings suggest Denisovans were the contemporaries of Neanderthals and even Homo sapiens (who first emerged about 300,000 years ago).
• DNA evidence suggests Neanderthals and Denisovans both lived in Denisova Cave, although probably not at the same time.

Denisovans discovery

• Denisovans were the first group of humans to be discovered based on their DNA alone.
• In 2010, German geneticist Prof Johannes Krause was extracting mitochondrial DNA from what he thought was a Neanderthal finger bone found in Denisova cave. It wasn’t Neanderthal but a new lineage, the Denisovans.
• The entire Denisovan genome sequenced while not having a single significant Denisovan fossil besides some small bone fragments, a few teeth and one pinky bone.
• In 2019, the right half of a mandible found during the 1980s in the Tibetan Plateau’s Baishiya Karst Cave was analysed. While no ancient DNA could be extracted from it, protein analyses indicated that it was
• In 2022, scientists identified a tooth unearthed at a cave in Laos as Denisovan, a clue that placed the species in Southeast Asia for the first time.

Denisovans appearance

• Denisovans had big teeth, a large stocky jaw and possibly a flattened and broad neurocranium (braincase).
• Denisovans wielded a wide pelvis, large ribcage and joint surfaces, low forehead and broader skull.
• Their appearance can be partly recreated through a new technique using DNA methylation.

Denisovans mate with Neanderthals

• One small 2.5cm bone fragment found at Denisova cave in 2012 and in 2018 it was announced that this 90,000-year-old bone belonged to Denny (as she was affectionately known), a girl who had a Neanderthal mother and a Denisovan father.

Crossbreeding benefits seen today

• The EPAS1 gene variant that modern Tibetans and Sherpas inherited from Denisovans makes them better adapted for living at high altitudes, protecting them from hypoxia (a condition where tissues in the body are deprived of oxygen).
• Scientists have even discovered that some modern populations in Oceania have an immune system that’s partly coded (and bolstered) by DNA acquired from Denisovans.

Denisovans Extinction debate

• No evidence of an environmental catastrophe.
• It’s certainly possible that Homo sapiens outcompeted the Denisovans, but there is no proof.
• They may have survived in New Guinea or its surrounding islands until 15,000-30,000 years ago.

Human Origin

Recent finding suggestion

According to scientists unlike Denisova Cave, which was occupied by early modern humans and Neanderthals as well as Denisovans, current evidence suggests that Denisovans were the only group of humans to live at Baishiya Karst Cave. That makes the Tibetan plateau — an area nicknamed “the roof of the world”.

NEANDERTHALS The name Neanderthal (or Neandertal) derives from the Neander Valley  in Germany, where the fossils were first found. Neanderthal member of a group of archaic humans who emerged at least 200,000 years ago during the Pleistocene Epoch. Neanderthals inhabited Eurasia from the Atlantic regions of Europe eastward to Central Asia. Features: Some defining features of their skulls include the large middle part of the face, angled cheek bones, and a huge nose for humidifying and warming cold, dry air. Their bodies were shorter and stockier than modern humans, another adaptation to living in cold environments.

Sources:

CNN,WikiPedia,BBC.

PRACTICE QUESTION Q. Baishiya Karst Cave often mentioned in news is associated with which of the following region? A.Nile River Basin B.Tibetan Region C.Siberian Region D.West Antarctica Answer B.