DNA that is left in the remains of long-dead plants, animals, or humans allows a direct look into the history of evolution. So far, studies of this kind on ancestral members of our own species have been hampered by scientists' inability to distinguish the ancient DNA from modern-day human DNA contamination. Now, research by Svante Pääbo from The Max-Planck Institute for Evolutionary Anthropology in Leipzig, published online on December 31st in Current Biology — a Cell Press publication — overcomes this hurdle and shows how it is possible to directly analyze DNA from a member of our own species who lived around 30,000 years ago.
The ability to sequence individual DNA strands allows the scientists to recognize which pieces of DNA really are ancient. So 30,000 year old DNA can be sequenced.
Using the remains of humans that lived in Russia about 30,000 years ago, Pääbo and his colleagues now make use of the latest DNA sequencing (i.e., 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. By contrast, DNA that is younger and only recently came in contact with the sample would consist of much longer fragments. This and other features, such as the chemical damage incurred by ancient as opposed to modern DNA, effectively enabled the researchers to distinguish between genuine ancient DNA molecules and modern contamination. "We can now do what I thought was impossible just a year ago – determine reliable DNA sequences from modern humans - but this is still possible only from very well-preserved specimens," says Pääbo.
I expect these 30,000 year old humans to be genetically different than us in important ways. For an argument on why that should be so see an excellent book by Greg Cochran and Henry Harpending entitled The 10,000 Year Explosion: How Civilization Accelerated Human Evolution.
|Share |||Randall Parker, 2010 January 03 11:45 PM Biotech Assay Tools|