Swimming hundreds of feet beneath the ocean’s surface in many parts of the world are prolific architects called giant larvaceans. These zooplankton are not particularly giant themselves but every day, they construct one or more spacious.

Sifting through teaspoons of clay and sand scraped from the floors of caves, German rese archers have managed to isolate ancient human DNA — without turning up a single bone. Their new technique, described in a study published on Thursday in the journal Science, promises to open new avenues of research into human prehistory and was met with excitement by geneticists and archaeologists.