Archaeological evidence has upended our image of Neanderthals in the last couple of decades. We've learned that these extinct human relatives may have decorated their bodies, buried their dead and even created art. These behaviors make them seem much more like our own species, Homo sapiens, than previously believed. And according to a new study in the journal PLOS ONE, we can add another skill to the Neanderthals' resume: diving for clams.

About 90,000 years ago, Neanderthals living on the Italian Peninsula between what is now Rome and Naples waded offshore into the Mediterranean Sea. Seeking clam shells, they reached their hands underwater, and perhaps even held their breath to swim down to the sandy seafloor. Back on the beach, they broke open the mollusks and maybe enjoyed eating some of the raw meat inside, but they were primarily interested in the shells themselves.

With thin, sharp edges, these shells were essentially natural knives. Instead of spending the better part of a day carving blades from hunks of rock, Neanderthals could find the tools by venturing to the beach. They might have gathered some dead and dried out clams that had washed up on the shore, but the living clams still underwater, though harder to get, were likely prized for their thicker shells.

These Neanderthals retouched their shell tools, chipping away the edges with stone hammers to further sharpen the edges, and they took a good number of these knives back to a shelter at the base of a limestone cliff. When archaeologists examined a cave in the cliff known as Grotta dei Moscerini in 1949, they found 171 examples of retouched tools fashioned from clam shells. At that time, however, it wasn't clear whether the shells had been plucked off a beach or sourced live from the water.

A team of researchers led by Paola Villa, an archaeologist at the University of Colorado Boulder, recently revisited the collection of shell tools from Grotta dei Moscerini and found revealing new details. Most of the shell tools had abraded surfaces, which one would expect of dry shells picked off a beach. But nearly a quarter of the clam shells had shiny, smooth exteriors, typical of shells picked live from the seafloor. In their new study, Villa and her colleagues conclude that diving for clams may have been a routine part of Neanderthal life in this region.

"There's this debate that's been going on for the better part of a century about the extent to which Neanderthals had the same behavioral repertoire as modern humans," says Erik Trinkaus, an archaeologist at Washington University in St. Louis who wasn't involved in the new study. Fishing and using coastal resources were thought to be unique behaviors to modern humans, he says, but over the last decade or so, "a number of examples have come out of excavations around Europe that have shown that Neanderthals were perfectly capable of exploiting marine resources."

At other Neanderthal sites in Europe, archaeologists have found additional shell tools as well as the remains of freshwater fish and mussels. In a study published last year, Trinkaus and his colleagues showed that a bony growth in the ear canal caused by repeated exposure to cold water, sometimes called swimmer's ear or surfer's ear, was common among Neanderthals, an indication that our extinct cousins habitually went to the coasts and rivers searching for food and other raw materials.

Villa and her colleagues don't know what Neanderthals were cutting with their shell tools at Grotta dei Moscerini, but the researchers also found a collection of pumice stones from the cave, which may have been abrading or polishing tools, similar to modern sandpaper. These stones were likely created during volcanic eruptions to the south in places like Mount Vesuvius and scooped up by Neanderthals as they washed up on the nearby beach.

The place where the artifacts were found in Grotta dei Moscerini is no longer accessible because it was buried under rocky debris that was blasted from the side of the hill during the construction of a coastal highway in the early 1970s, according to Villa. "Re-excavating the site will not be easy at all," she says, and right now the team has no plans to try.

Trinkaus says the new study "reinforces what is becoming increasingly evident from a variety of different sources of archaeological data: Neanderthals were able to do, and occasionally did, most of these kind of behaviors that had been considered to be special to modern humans." The bias against Neanderthal abilities may simply be due to a lack of widespread archaeological evidence.

Unfortunately, the coastal sites that might help bolster the case for Neanderthal beach activities are rare, and many are now underwater. During the time that Neanderthals and humans shared the planet, the climate was much colder and ice sheets stretched over larger parts of the European continent. But at the end of the last ice age, between about 19,000 to about 6,000 years ago, sea levels rose around the world by about 400 feet, swallowing the once-shoreside campsites of prehistory.