A cave in Russia | Blogotariat

Denisova cave, situated in the foothills of Siberia’s Altai Mountains, is the only site in the world known to have been occupied by both archaic human groups (Neanderthals and Denisovans) at various times, as well as by us ‘modern’ humans.

New studies show that the cave was occupied by people from at least 200,000 years ago, with stone tools in the deepest deposits suggesting human occupation may have begun as early as 300,000 years ago. Neanderthals visited the site between 200,000 and 100,000 years ago, with a girl of mixed ancestry (‘Denny’), revealing that the two groups of hominins met and interbred around 100,000 years ago, the first direct evidence of interbreeding between two archaic hominin groups (Denisovan father, Neanderthal mother)1.

Denisova cave first came to worldwide attention in 2010, with the publication of the genome obtained from the fingerbone of the girl belonging to a group of humans not previously identified in the palaeoanthropological record; the Denisovans. Further revelations followed on the genetic history of Denisovans and Altai Neanderthals, based on analysis of the few and fragmentary hominin remains. Most of the evidence for Neanderthals at Denisova Cave falls within the last interglacial period around 120,000 years ago, when the climate was relatively warm, whereas Denisovans survived through much colder periods, too, before disappearing around 50,000 years ago2.

Unless you live in a similar cave, you will have heard of Neanderthals, Peking Man, Java Man and all the discoveries in west Africa, but may not have heard of the Denisovans, as they are a relatively recent discovery. In addition, the Denisovans are the first ancient hominin species to be revealed by their DNA alone, not by the morphology of their fossils. The girl’s finger bone from which the DNA was extracted has been dated from about 60,000 to 80,000 years ago. While placed in the genus Homo, they have not yet been given a species classification as no physical description is possible3.

More recently, the genome of another Denisovan has been sequenced from a specimen from the same cave. At 200,000 years old, it is the oldest human DNA (by some 80,000 years) to be extracted from a fossil. This DNA is from a male and came from a separate population of Denisovans from the previously analysed girl3.

At the other end of the Denisova age scale, is a woman who held a deer-tooth pendant some 20,000 years ago, and who left her DNA on the ancient artefact. The woman’s DNA was extracted from inside pores of the tooth. Comparing her genetic sequence with other sets of ancient DNA showed that she was a member of our species, Homo sapiens, and had north Eurasian ancestry4.

The ability to obtain this amount of detail from DNA began over 40 years ago. Biochemist Kary Mullis says he was driving to his cabin in Mendocino, California in 1983 when suddenly, like a bolt of lightning, he came up with a way to pinpoint a particular stretch of DNA and synthesise an enormous number of copies. For this, Mullis won the 1993 Nobel Prize in Chemistry for inventing polymerase chain reaction, or PCR. Before PCR, studying DNA was difficult. Isolating exactly the right small snippet of DNA to study was extremely difficult. Even if it was possible to isolate a section of interest, the amount of material was often so minuscule that there just wasn’t much available to study5. PCR changed all that and allows the DNA from a couple of cells trapped in the finger bone of a girl who died many thousands of years ago, to be copied millions of times and thereby analysed.

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