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Scientists have reconstructed a 2-million-year-old ecosystem from ancient DNA

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“A new chapter spanning 1 million years of history has finally been opened and for the first time we can directly observe the DNA of an ecosystem from the past so far in time,”

 

says geneticist Eske Willerslev of the University of Cambridge in the UK and the University of Copenhagen in Denmark. In fact, thanks to a series of samples collected from the ice and permafrost of the Kap København geological formation, at the mouth of a fjord in northern Greenland, scientists have had the opportunity to recover and reconstruct the environmental DNA of 2 million years ago, a million years older than the previous record, which is DNA from a woolly mammoth that lived 1 million years ago.

Scientists obtained most of these samples while doing other work some time ago. The 41 usable samples were extracted from clay and quartz. They remained in storage, waiting for the right design: “Only when a new generation of DNA extraction and sequencing equipment was developed were we able to locate and identify extremely small and damaged DNA fragments in sediment samples , which have been preserved in ice or permafrost and, crucially, have not been disturbed by humans for 2 million years,” explains geologist Kurt Kjær of the University of Copenhagen.

The DNA recovered from the samples, after a long work, would have been unusable just a few years ago: the fragments were tiny, just 1 nanometer long, highly degraded and very incomplete.

 

This astonishing work has allowed scientists to reconstruct an ancient landscape, revealing a world very different from the frigid shores of the Arctic Circle.

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The temperate climate of the Arctic Circle

This reconstruction revealed a variety of life forms compatible with a surprisingly temperate climate . Scientists have found animals related to reindeer and caribou, geese , hares and, interestingly, mastodons (mammoths). Ants , fleas, corals and crabs have also left their mark in the sediments, as have birches and poplars. Other DNA samples – collected from microorganisms and fungi – are still being identified. A future paper will describe the full extent of the ecosystem to the best of scientists’ knowledge. However, some features suggesting a much warmer climate in the region during the Early Pleistocene are already noted,considerably hotter than current temperatures.

According to the researchers, this is an allusion to the future of the Earth in the face of a changing climate. “One of the key factors is to what extent species will be able to adapt to changing conditions resulting from a significant increase in temperature. The data suggest that more species may be evolving and adapting to wildly variable temperatures than previously thought,” says geogeneticist Mikkel Pederson of the University of Copenhagen.

 

For scientists, this work represents a huge step forward. Now that environmental DNA has been successfully extracted and interpreted, it may be possible to do the same with ancient deposits elsewhere. “If we can start exploring the ancient DNA in clay grains from Africa, we may be able to glean groundbreaking information about the origin of many different species, perhaps even new knowledge about early humans and their ancestors,” he says. Willerslev.

The research was published in Nature.

  • A 2-million-year-old ecosystem in Greenland uncovered by environmental DNA. (nature.com)
 
 

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