Ed Yong in The Atlantic:
Around 45,000 years ago, in a Belgian cave, a Neanderthal died. As its body decayed, its cells split apart, spilling their contents onto the cave floor. Those remnants included the Neanderthal’s DNA, some of which stuck to minerals in the sediment. There, leashed to the very rock, the DNA persisted, long after its owner’s body had disappeared and its bones had been carted off by scavengers. And in 2015, a group of scientists scooped it up.
Viviane Slon from the Max Planck Institute for Evolutionary Anthropology and her colleagues have now managed to extract and sequence the DNA of ancient animals from sediment that’s up to 240,000 years old. By doing so, they can infer the presence of Neanderthals, Denisovans, and other extinct hominids without ever having to find their bones. “We were surprised by how well it works,” says Slon. “The success rates were amazing.”
“I absolutely loved this,” says Jennifer Raff, who studies ancient DNA at the University of Kansas, and who was not involved in the study. “Although people have been working on recovering ancient DNA from sediments for a few years now, this is unprecedented in scope and success. My notes on the paper are full of exclamation marks. Woolly rhinoceros! Woolly mammoth! Cave bear! Neanderthal and Denisovans!”
Animals have a vast genetic aura that extends beyond their physical bodies into the world around them. Their DNA falls to the ground in balls of dung, zips through the air in blood-sucking insects, and leaches into the soil during decomposition. Scientists who study living animals have used this environmental DNA (eDNA) to identify everything from elephants and earthworms. They can conduct a census of the natural world without needing to spot any actual animals—a boon when working with rare or hard-to-spot species in inaccessible habitats.