A human ancestor carved a zigzag onto the shell of a mussel some 430,000 years ago. Now that shell, recovered from a riverbank in Indonesia in 1891, could alter our understanding of what it means to be human. Artistic creativity has long been considered unique to Homo sapiens: Before the shell's discovery, the earliest evidence of geometric art came in the form of rock scratches dated to no older than 100,000 years ago, National Geographic reports. But this latest find, described in Nature, is "at least four times as old," a study author tells NPR. In fact, it dates to the time of Homo erectus, a species older than Neanderthals that's described by the Smithsonian as being "the oldest known early humans to have possessed modern human-like body proportions."
The shell was never described by its finder, but seven years ago, Josephine Joordens and a colleague noticed the zigzag marking. She began studying it and ruled out that it was made naturally or by animals. As she tells Nature, there aren't any gaps in the engraving, suggesting it was "made by an agent who did a very deliberate action." Further, her team tried to re-create the pattern and discovered it was pretty tough to do so. As for whether it should be considered art, Joordens says it's really impossible to say since we don't know "the intention of the person who made it." An anthropology professor is even more hesitant to see it as a sign that Homo erectus was capable of artistic creativity: "If this is symbolic behavior by Homo erectus, then it's basically the only evidence we've got [of that] for a species that lived for a million-and-a-half years on three continents." (Cave paintings are also changing the story of ancient art.)