Skip to main content

A two million-year-old DNA sample has could provide a “game-changing” understanding of the world’s ancient ecosystems and how the environment could change due to the climate crisis.

The new sample, made up of microscopic fragments of environmental DNA, was found in ice age sediment in northern Greenland and is one million years older than the previous record for DNA, which came from a Siberian mammoth bone.

The ancient DNA has already been used to map some of the components of a two-million-year-old ecosystem “which weathered extreme climate change“, the research team led by academics at Cambridge and the University of Stockholm said.

They also believe the results could help predict the long-term environmental toll of today’s global warming.

“A new chapter spanning one million extra years of history has finally been opened and for the first time, we can look directly at the DNA of a past ecosystem that far back in time,” said Professor Eske Willerslev a Fellow of St John’s College, Cambridge and who also works at the University of Stockholm.

“DNA can degrade quickly but we’ve shown that under the right circumstances, we can now go back further in time than anyone could have dared imagine.”

His colleague at the University of Stockholm’s Lundbeck Foundation GeoGenetics Centre, Professor Kurt Kjær, an expert in geology, said the samples had been well-protected from any human impacts over the past two million years.

He said: “The ancient DNA samples were found buried deep in sediment that had built up over 20,000 years.

“The sediment was eventually preserved in ice or permafrost and, crucially, not disturbed by humans for two million years.”

The researchers said the pieces of DNA they have examined were incomplete samples, a few millionths of a millimetre long.

They were taken from a sediment deposit almost 100 metres thick, known as the København Formation, which is in the mouth of a fjord in the Arctic Ocean at Greenland’s northernmost point. Two million years ago the climate in Greenland varied between Arctic and temperate and was between 10-17C warmer than Greenland is today. The sediment built up metre by metre in a shallow bay.

The team said they also discovered evidence of microorganisms, animals and plants including reindeer, hares, lemmings, birch and poplar trees.

They even found that mastodon, an ice-age elephant-like mammal, roamed as far as Greenland before later becoming extinct. Previously it was thought mastodons’ range did not extend as far as northern Greenland all the way from its known origins in North and Central America.

In order to make a comprehensive assessment of the DNA fragments, 40 researchers from Denmark, the UK, France, Sweden, Norway, the USA and Germany worked on the samples.

“The process was painstaking”, the researchers said.

When they found the DNA, the researchers compared every single DNA fragment with extensive libraries of samples collected from present-day animals, plants and microorganisms.

“A picture began to emerge of the DNA from trees, bushes, birds, animals and microorganisms” from the world 2 million years ago.

They said some of the DNA fragments were easy to classify as predecessors to present-day species, while others could only be linked at genus level, and some originated from species impossible to place in the DNA libraries of animals, plants and microorganisms still living in the 21st century.

The two-million-year-old samples also helped academics build a picture of a previously unknown stage in the evolution of the DNA of a range of species still in existence today.

Professor Kjær said: “It wasn’t until a new generation of DNA extraction and sequencing equipment was developed that we’ve been able to locate and identify extremely small and damaged fragments of DNA in the sediment samples. It meant we were finally able to map a two-million-year-old ecosystem.”

Assistant professor Mikkel W Pedersen, co-first author on the paper and also based at the Lundbeck Foundation GeoGenetics Centre, said: “The Kap København ecosystem, which has no present-day equivalent, existed at considerably higher temperatures than we have today – and because, on the face of it, the climate seems to have been similar to the climate we expect on our planet in the future due to global warming.

“One of the key factors here is to what degree species will be able to adapt to the change in conditions arising from a significant increase in temperature. The data suggests that more species can evolve and adapt to wildly varying temperatures than previously thought. But, crucially, these results show they need time to do this. The speed of today’s global warming means organisms and species do not have that time so the climate emergency remains a huge threat to biodiversity and the world – extinction is on the horizon for some species including plants and trees.”

The research team said they believed some of the “tricks” of the two-million-year-old plant DNA discovered could be used to help make some endangered species more resistant to a warming climate.

Professor Kjær said: “It is possible that genetic engineering could mimic the strategy developed by plants and trees two million years ago to survive in a climate characterised by rising temperatures and prevent the extinction of some species, plants and trees. This is one of the reasons this scientific advance is so significant because it could reveal how to attempt to counteract the devastating impact of global warming.”

The findings from the Kap København clay could now open up a whole new period in DNA detection, if scientists target similar geological formations.

Professor Willerslev explained: “DNA generally survives best in cold, dry conditions such as those that prevailed during most of the period since the material was deposited at Kap København. Now that we have successfully extracted ancient DNA from clay and quartz, it may be possible that clay may have preserved ancient DNA in warm, humid environments in sites found in Africa.

“If we can begin to explore ancient DNA in clay grains from Africa, we may be able to gather ground-breaking information about the origin of many different species – perhaps even new knowledge about the first humans and their ancestors – the possibilities are endless.”

The research is published in the journal Nature.

Source link

Leave a Reply