for National Geographic News
The oldest known strands of DNA have been recovered from frozen mud taken from the base of Greenland's ice sheet, according to a new study.
The discovery could rewrite what was thought about Greenland's ecological past—and could alter current predictions about how global warming will affect the island's ice.
Today most of the Danish-owned island is covered with an ice sheet up to two miles (three kilometers) thick.
But the newfound DNA—genetic material from pine trees, butterflies, and other organisms that lived as much as 800,000 years ago—tells a story of a much greener and vibrant past.
Hundreds of thousands of years ago southern Greenland had thriving forests similar to those in northern Canada today, says an international team of 30 scientists led by Eske Willerslev of the University of Copenhagen in Denmark.
The find surpasses the previous record for the oldest DNA, which came from mammoths and other animals frozen in Siberia about 300,000 to 400,000 years ago.
The study also implies that Greenland's ice sheet did not melt as much as computer models have predicted during a period 125,000 years ago, when Earth's sea level rose dramatically.
This raises the question of where the water actually came from.
The research is described in tomorrow's issue of the journal Science.
At a site in the center of southern Greenland, researchers drilled through the thick ice until they reached the bottom layer of frozen mud, similar to the permafrost now found across areas such as Siberia.
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