London, Jan 1 (IANS) Researchers have developed a foolproof way to analyse DNA samples from human remains 30,000 years ago, allowing a direct look into the history of evolution.
DNA - the hereditary material contained in the nuclei and mitochondria of all body cells - is a hardy molecule and can persist, conditions permitting, for tens of thousands of years.

Using ancient DNA extracted from bones, the biology of extinct animals, such as mammoths, as well as of ancient humans (the Neanderthals), has been successfully studied in recent years.

But the special probes that made them possible, cannot distinguish whether the DNA comes from the ancient human sample or was introduced much later, for instance by the archaeologists who handled the bones. Thus, conclusions about the genetic make-up of ancient humans of our own species were fraught with uncertainty.

Using the remains of humans that lived in Russia about 30,000 years ago, Svante Pääbo from the Max-Planck Institute for Evolutionary Anthropology in Leipzig, Pääbo and his colleagues made use of the latest DNA sequencing (reading the sequence of bases that make up the DNA strands) techniques to overcome this problem.

These techniques, known as “second-generation sequencing”, enable the researchers to “read” directly from ancient DNA molecules, without having to use probes to multiply the DNA.

Moreover, they can read from very short sequence fragments that are typical of DNA ancient remains because over time the DNA strands tend to break up, said a Max-Planck release.

Conversely, DNA that is younger and only recently came in contact with the sample would consist of much longer fragments.

The findings were published online in the Thursday edition of Current Biology - a Cell Press publication.