Estatuas cave in northern Spain was a hive of activity 105,000 years ago. Artifacts show its Neanderthal inhabitants hafted stone tools, butchered red deer, and may have made fires. They also shed, bled, and excreted subtler clues onto the cave floor: their own DNA. “You can imagine them sitting in the cave making tools, butchering animals. Maybe they cut themselves or their babies pooped,” says population geneticist Benjamin Vernot, a postdoc at the Max Planck Institute for Evolutionary Anthropology (MPI-EVA), whose perspective may have been colored by his own baby’s cries during a Zoom call. “All that DNA accumulates in the dirt floors.”