Denisovans are early species closely related to the Neanderthals which got extinct. Around 60,000 years ago, human ancestors moved out of Africa along with hominids Neanderthals and Denisovans. Neanderthals settled in Europe and western Asia.
In 2008, a 40,000 years old adult tooth was excavated from a cave in southern Siberia. Along with this, a preserved pinkie bone of a 5 – 7-year-old young girl was found. The DNA was extracted from the pinkie bone and compared with the genome sequence of Neanderthals and modern humans.
The results indicated that the girl was more closely related to Neanderthals yet was different from them. The scientists named the new species as Denisovan (after the name of the cave).
There was genetic overlap was found between East Asians, Melanesians (Pacific Islanders) and Denisovan genome. Almost 3 to 5 percent of the genetic material of Melasians came from Denisovans. This gives rise to the theory that Denisovans interbred with ancestors of Melanesians. About 45,000 years ago, the Denisovan DNA was carried on by Melanesians after reaching the Papua New Guinea. The genetic diversity indicates that even though the numbers weren’t high, Denisovans were spread widely across Asia.
THE CHANGED VIEW OF HUMAN EVOLUTION
Earlier, it was believed that Homo Sapiens has evolved from Homo Erectus around 2,00,000 years ago in East Africa. From there, the humans had spread to Europe and rest of the world.
However, with the recent discoveries regarding Denisovans and Neanderthals, the date for human origin has shifted back to 3,00,000 years ago. In the 1960s, few miners found fossils and stone tools that were pegged to be 40,000 years old. However, when the specimens were analysed recently by using thermoluminescence, they were found to be 300,000 years old.
Scientists also discovered that the fossils were not modern humans but other closely related species. The brain was less developed and there were differences in DNA. This gave evidence for the evolution of brain with age. The ancestors interbred and spread their genes, leading to genetic diversity.
THE BOTTOM LINE
Scientists are comparing the genomes of apes, Neanderthals, Denisovans and modern humans for identification of unique DNA segments of the groups. There have been genetic changes regarding brain function, development of language and nervous system after the split from Denisovans. By examining these changes, it can be understood why humans survived while others were extinct.
These discoveries are making the story of human evolution more complex and fascinating. In the past, it has already been established through DNA evidence that modern humans interbred with Neanderthals and Denisovans. This changes the overall history of human evolution.