Fossil DNA proves Neanderthals were not ancestors of humansAnjali Mody
LONDON, JULY 11: The theory that modern humans descended from Neanderthals has been proved wrong by scientists who have worked on Deoxyribo Nucleic Acid (DNA) extracted from a 30,000 year old, fossilised bones of a Neanderthal man. The scientists, led by Svante Paabo of the University of Munich, said that their research established that Neanderthal man was too distant genetically to have been an ancestor of modern man.
The findings have been published in the journal Cell. Using techniques that determine how closely living beings are genetically related, they established that the ancestors of Neanderthals branched off from the human family tree some 600,000 years ago. Neanderthals looked like human beings, had large brains, stood erect and used tools. There is evidence that Cro-Magnon people, who became modern humans, lived at the same time as Neanderthals and interacted with them. According to Chris Stringer, an expert in early humans at London's Natural History Museum, some ancient tools and jewellery indicate they may have traded. But, he says, ``It does not look like they interbred with our ancestors.''
Stringer said that the finding was ``equivalent to landing the Pathfinder on Mars and getting it to work. ``I have not encountered anyone in the scientific world who doubts that they have recovered Neanderthal DNA. We know if anything is a Neanderthal, this is a Neanderthal. ..One couldn't have hoped for a better specimen,'' he added.
Stringer said that the finding would tip the balance in the often bitter dispute about how humans evolved. Those who traced the evolution of modern humans to Neanderthals, who died out about 30,000 years ago, held that there was a `missing link' between Neanderthals and Homo Sapiens. Stringer said the evidence firmly supported the `Out of Africa' theory of human origin. Those, like Stringer, who subscribe to this theory say modern humans evolved in Africa and spread across the world about 1,00,000 years ago.
The other, competing theory is that Homo Erectus - an early ancestor of modern humans - moved out of Africa and across the world and that modern humans evolved separately in several different regions. Both these theories were reached by examining fossils. But, as an excited Stringer said, ``Now we have a completely different approach, and about 1,00,000 years ago our real ancestors emerged from Africa.''
Paabo said that the DNA came from the first skeleton of a Neanderthal found in Germany's Neander Valley in 1856. ``The fossil we have worked with is not just any Neanderthal....it is the Neanderthal that has given the name to the species.''
The work was difficult, Paabo admits, particularly as the techniques used were sensitive and tended to pick up outside DNA contamination. He also said the bones had been shellacked, which could have preserved the DNA and protected them from contamination by modern DNA.
He said his team ran four separate tests for authenticity - checking whether other amino acids had survived, making sure the DNA sequences they found did not exist in modern humans, making sure the DNA could be replicated in their own lab and then getting other labs to duplicate their results. Comparisons with the DNA of modern humans and of apes showed the Neanderthal was about halfway between a modern human and a chimpanzee.
Thomas Lindahl, a DNA expert for Britain's Imperial Cancer Research Fund, said, ``It's a real tour de force and probably the most important work that has been done so far on ancient DNA.''
Lindahl also expressed his surprise that the DNA, which usually degrades easily, had survived for so long. Paabo explained that the DNA survived most probably because the fossil came from the cold north of Germany. Efforts to get DNA from fossils from the Middle East had so far failed.