What was the world like two million years ago? By analyzing the DNA of the earliest ancient environment recovered so far, scientists have mapped the appearance of the ecosystem in northern Greenland about 2 million years ago, including animal and plant species that once existed. The result was published in the journal Nature on the 7th, enabling people to explore and understand an ancient ecosystem to an unprecedented extent, revealing an ecosystem without modern equivalents. The reconstruction site is a polar desert, located in the Peary Land of Northern Greenland. Previous studies have shown that the climate in this region was much warmer about 2-3 million years ago, and the temperature was 11 ℃ - 19 ℃ higher than now. However, due to the scarcity of vertebrate fossils, people did not know much about the biological communities living in the Arctic at that time. This time, researchers from the University of Cambridge, England, extracted and sequenced DNA from 41 organic matter enriched sediment samples collected from 5 different sites in the reconstruction site. The research team used these DNA to reproduce the appearance of the ancient ecosystem: an open northern forest with poplar, birch, arborvitae and various Arctic and northern shrubs and herbs. DNA records confirmed the existence of hares. Mitochondrial DNA from the site also revealed traces of other animals, including mastodon, reindeer, rodents and geese. The researchers also recovered the ancient DNA of marine organisms, which showed that there was once a population of Atlantic horseshoe crab. The researchers believe that this may mean that this area had a warmer surface water environment in the early Pleistocene, consistent with previous predictions. The researchers said their research results demonstrated the potential of using ancient environmental DNA to trace the evolution of biological communities 2 million years ago. (Liu Xinshe)