DENISOVA HOMININ : - AN EXTINCT HUMAN SPECIES

Neanderthals were very early humans who lived in Europe & Western Asia from about 400,000 years ago until they became extinct about 40,000 years ago. 

Denisovans are another population of early humans who lived in Asia & were distantly related to Neanderthals. Much less is known about the Denisovans because scientists have uncovered fewer fossils of these ancient people.

Research has shown that modern humans overlapped with Neanderthal and Denisovan populations for a period, and that they had children together (interbred). 

As a result, many people living today have a small amount of genetic material from these distant ancestors.

Svante Paabo & his team in 2008 in Germany have sequenced nearly all the genome of the Denisovan people, an extinct human-like species contemporary with the Neanderthals. 

The work by the Max Planck Society's Evolutionary Anthropology Institute in Leipzig has been first time obtained full genetic data of any of the archaic hominins. 

The group worked with less than 10 milligrams of DNA from the finger bone of a female. The bone fragment, found in the Denisova Cave in Altai mountain region in Siberia in debris 30,000 to 50,000 years old, was the first evidence of the existence of the vanished species. These were the remains of a hybrid girl of a Neanderthal mother and Denisovan father, named ‘Denny’. 

The 2022 Nobel Prize winner for Physiology or Medicine Swedish geneticist Svante Pääbo for his research in the field of genomes of extinct hominins and human evolution.

He discovered that, the archaic gene sequences from our extinct ancestors influences the physiology of present-day humans. Like the, Neanderthal genes that affect our immune response to different types of infections. 

Dr. Pääbo’s research has resulted in the rise of a new scientific discipline called paleogenomics, which is the study and analysis of genes of ancient or extinct organisms. 

He was  studying mitochondrial DNA from Neanderthals. Mitochondria, popularly called the powerhouse of the cell, is an organelle inside the cell that has its own DNA. 

Comparisons with DNA sequences of contemporary humans from different parts of the world also suggested gene flow between them and Denisovans.  

The analysis of mtDNA  shows that the Denisova Cave individual differed from modern humans much more than what is seen between Neanderthals and modern humans. 

The Denisova individual has about twice the number of mtDNA differences with modern humans compared with that of the Neanderthal and modern human. Neanderthal mtDNA differs from modern humans at an average 202 nucleotide positions; the Denisova individual differs at about 385 positions.

The study has  great evolutionary significance in humans history. mtDNA data clearly shows that the Denisova hominin lineage branched off well before modern human could branch off from Neanderthal. 

Humans diverged from chimpanzee mtDNA about 6 million years ago. Using this data, the most recent date when the Denisova hominin, Neanderthal and modern human shared a common ancestor is about 1 million years ago. 

Hence, the divergence of Denisova hominin should have happened less than 1 million years ago.

According to, stratigraphic & other evidences, the Denisova individual lived between 30,000 & 50,000 years ago. Individuals carrying Neanderthal mtDNA lived at the same time.

 Evidence of Homo floresiensis who lived in Indonesia about 17,000 years ago was shown by an earlier study. The Denisova individual from Siberia appears to have lived about 40,000 years ago. This indicates that several hominin lineages had coexisted for long periods of time.

The hominin migration out of Africa was episodic and not at a single instant. The period when the first hominin, Homo erectus, left Africa was about 1.9 million years ago. Genetic & archaeological data indicates that two other groups of hominin had left Africa after H. erectus .  

These groups are the ancestors of Neanderthal that left between 5,00,000 and 3,00,000 years ago, and the second group being the anatomically modern humans that left about 50,000 years ago.

The group that left Africa between 5,00,000 and 3,00,000 years ago is presumed to be the Homo heidelbergensis or Homo rhodesiensis .

Several fossil remains of Neanderthal have been recovered and extensive mtDNA sequencing done. However, remains of other hominins have been scarce. That is because the environment in the equatorial and tropical regions is not conducive for long-term preservation of DNA in bones, teeth and other remains.

The recent extraction of both mtDNA and nuclear DNA from hair samples of a male palaeo-Eskimo found in permafrost deposits in Greenland raises the possibility of hair becoming a more resilient source to preserve DNA.

Whether they will be capable of preserving the DNA in hostile environments remains to be seen.

Species such as Homo Longi have  been identified in 2018. There are now 21 known species of human. But Homo sapiens weren’t the inevitable evolutionary destination. Nor do they fit into any simple linear progression or ladder of progress. 

Homo naledi‘s brain may have been smaller than that of a chimpanzee but there is evidence they were culturally complex and mourned their dead.

Neanderthals created symbolic art but they weren’t the same as us. Neanderthals had many different biological adaptations, which may have included hibernation. Hybrid species of human , may have played a key role in our evolution. Evidence of the importance of hybrids comes from genetics. “Denny,” a girl with a Neanderthal mother and Denisovan father is an example of this evolution. 

The origins of our own species coincided with major shifts in climate as we became more distinct from other species at these points in time. All other species of human seem to have died out as a result of climate change.

Three major human species Homo erectus, Homo heidelbergensis, and Homo neanderthalensis died out with major shifts in climate like a temporary breakdown of Earth’s magnetic field 42,000 years ago, which coincided with the extinction of the Neanderthals.

DNA sequences from Neanderthals were also found to be more similar to sequences from contemporary humans originating from Europe or Asia than to contemporary humans originating from Africa, suggesting interbreeding between Neanderthals and Homo sapiens during their coexistence.

Contrary to popular belief that high altitude regions were inhabited only by modern humans dating back to less than 40,000 years, the fossil remains conclusively prove that Denisovans lived in the Tibetan Plateau at an altitude of 3,280 metres much earlier i.e. 1,60,000 years ago. The Denisova cave in Siberia is at an altitude of just 700 metres.

Previous genetic studies have found that modern humans living in the Tibetan Plateau carried a special gene variant — EPAS1 (Endothelial PAS Domain Protein 1) — that allowed them to cope with low oxygen (hypoxia) environments typical of high altitude. This gene variant has been found in Denisovans.

Since the Denisova cave is at an altitude of just 700 metres, it was not clear why and how the Denisovans possessed this adaptation. The discovery of a Denisovan sample in the Tibetan plateau at a high altitude provides the answer.

The possible explanation for the presence of this gene variant in the hominin is that Denisovans lived for a long time in the plateau leading to the gene mutation. This mutation has later been passed on to modern humans.

The team initially found 61 genes that differed between modern humans and our extinct relatives . One of these altered genes – NOVA1 is a master gene regulator, influencing many other genes during early brain development. 

Versions of another gene — PPARA — found in highlanders allow them to metabolise fuels such as sugars more efficiently. David Reich, a Harvard geneticist who worked on the study said that, Denisovan material has contributed three to five per cent of the genomes of people in Australia and New Guinea and aboriginal people from the Philippines, and some of the islands nearby.

Denisovans had  dark skin, brown hair and brown eyes, a robust jaws, a low forehead, a large ribcage and a wide pelvis. The analysis also indicated Denisovans had a wider face than Neanderthals and our own species, and a more protruding face than our own species but less so than Neanderthals. 

The researchers examined sites in the genome where Neanderthal and Denisovan genetics differ. At each of these locations, they compared fragments of Denny's DNA to the genomes of the two ancient hominins.

In more than 40% of cases, one of the DNA fragments matched the Neanderthal genome, whereas the other matched that of a Denisovan, suggesting that she had acquired one set of chromosomes from a Neanderthal and the other from a Denisovan. That made it clear that Denny was the direct offspring of two distinct humans.

According to  Kelley Harris, a population geneticist at the University of Washington, Denny’s specimen is indeed a first-generation hybrid. Harris says that sexual encounters between Neanderthals and Denisovans might have been quite common.

It implies that, such hybrid offsprings could be widespread. So if Neanderthals and Denisovans mated frequently, why did the two hominin populations remain genetically distinct for several hundred-thousand years?
Harris suggests that Neanderthal–Denisovan offspring could have been infertile or otherwise biologically unfit, preventing the two species from merging. 

According to, Joshua Akey, a population geneticist at the University of Washington, vast numbers of Neanderthal genes are not carried by  the contemporary humans. This is a strong indication that the genes were harmful to human , Neanderthal hybrids and their descendants, so were purged as the descendants continued to mate.

Akey’s team found that one large chunk of modern-human genome that bears no Neanderthal contributions is the one that encompasses the gene FOXP2, which is involved in speech in humans. Pääbo agrees that Neanderthals and Denisovans would have readily bred with each other when they met , but he thinks that those encounters were rare.