Posted on 5 July 2007
Scientists from Copenhagen University working with researchers in Europe, Australia and Canada have discovered that the Arctic island, more than 80 per cent of whose surface is now under ice, was covered by a forest approximately 450,000 years ago.
The DNA is probably between 450 and 800 thousand years old making it the oldest authenticated DNA to date
Professor Eske Willerslev, University of Copenhagen
A research team at the University of York, part of the new Palaeo group, played an important role in the discovery published in the latest issue of Science. They were sent tiny samples of dirty ice from the base of the ice-cap and were surprised by how well the proteins were preserved.
Dr Enrico Cappellini said "The work was very difficult. The amino acid levels in what amounted to a few drops of dirty water were so low we had to run many blank samples before we were happy that the ‘fresh’ protein was not simply contamination."
At one site on the southern Greenland ice sheet, preservation was particularly good - levels of protein damage were lower than in a 10-year-old coral. These samples were analysed for DNA by the Copenhagen team and their results were so remarkable, they were then cross-checked by labs across the world. The dirty ice with damaged proteins yielded nothing, but the fresher site, revealed a conifer forest full of insects; but how long ago?
Professor Matthew Collins, who headed the research at York, added: "This was our next challenge. The Danish team modelled the temperature history of the different ice cores and we used these to calculate the approximate ages of the samples".
The York team had presumed that the low level of damage would mean that the site was young, but the modelling suggested it was, surprisingly, more than 100,000 years old. One school of thought attributes the rise in sea level 130,000 years ago as largely due to the melting of the Southern Greenland ice. If the team’s age estimates are correct, the melting was not as extensive as models suggest.
The team used a similar approach to estimate the age of the earliest evidence of human occupation in North West Europe. Dr Kirsty Penkman, another member of the York team, said: "The amino acid dating method is more problematic in samples such as this, so we can’t really be confident of the age".
Researchers in Copenhagen team therefore used a further three methods, all of which indicated an age older than the last inter-glacial.
Professor Eske Willerslev of the University of Copenhagen who headed the research. said: "The DNA is probably between 450 and 800 thousand years old making it the oldest authenticated DNA to date. At the same time the DNA represents the youngest evidence of native conifer forest in Greenland."
The research also indicates a way of solving one of the major difficulties facing paleontologist -- obtaining fossil data from the 10 per cent of the Earth's terrestrial surface that is covered by thick glaciers and ice sheets.