In 1949, archaeologists found 171 clamshells and 49 pumice stones and fragments in a seaside cave near Gaeta, south of Rome.
Animal teeth found alongside the tools were dated to between 90,000 and 100,000 years ago, when Neanderthals are thought to have been the only hominins living in Western Europe.
The actual origins of the clams, however, were overlooked, and it had remained that way for the past 70 years.
Now, a new paper published in the journal PLOS One argues that the Neanderthals didn’t just gather the dead material from the nearby beaches – they actually dove into the Mediterranean for it themselves.
The tools, which are thought to have been used as scrapers, were made from the shell of a clam known as Callista chione, which lives in coastal waters at least three feet deep.
By looking at the degree of wear on some of the shells, which remained shiny, experts determined that the clams weren’t scavenged off the dry sand but rather they were plucked directly from their burrows under the sea.
It is unclear whether the Neanderthals ate the clams.