Archaeologist Stephen Munro nearly fell off his chair when he noticed patterns of straight lines purposefully etched on a fossilized clamshell. The engravings were half a million years old, which meant they'd been made by a Homo erectus—an extinct human species that predated Homo sapiens by upwards of 300,000 years.
In addition to the engravings, Munroe and his colleagues found shells that were carefully crafted into specialized tools. Taken together, these discoveries suggest that Homo erectus was far more sophisticated than previously believed and capable of symbolic thought.
"It is a fascinating discovery," says Colin Renfrew, an archaeologist at the University of Cambridge. "The earliest abstract decoration in the world is really big news."