In the latest excavations, led by a multidisciplinary team that has been working since October 2019, researchers found hundreds of animal bones with signs they had been gnawed on by hyenas — the Stone Age ancestors to today’s carnivores — who used the cave as a sort of pantry, said Mario Rolfo, who teaches prehistoric archaeology at the University of Rome at Tor Vergata.

It appears that the hyenas also had a taste for Neanderthals, and one skull found at the site had a hole similar to the one found in the 1939 cranium. That find definitively put to rest Blanc’s theory of cannibalism and cult rituals.

“Reality is more banal,” Professor Rolfo said, adding that “hyenas like munching on bones” and probably opened a cavity in the skull to get to the brain.

It is unclear whether the Neanderthals were killed by the hyenas or the hyenas snacked on Neanderthals after they died from other causes.

“What it does mean is that there were many Neanderthals in the area,” Professor Rolfo said.

Neanderthals flourished in Europe for about 260,000 years, until roughly 40,000 years ago, though the dating is subject to much scholarly debate. Their bones have been found at sites across Europe and western Asia, from Spain to Siberia. But “finding so many in one site is very rare,” said Francesco Di Mario, the Culture Ministry archaeologist in charge of the excavation.

The recovery of new fossil remains, along with the 1939 findings, makes the cave “one of the most important Paleolithic sites in Europe and the world,” he said.

Italy’s culture minister, Dario Franceschini, called the finds an “extraordinary discovery” that enriches research on Neanderthals.

The site was particularly well preserved because a prehistoric landslide had closed the entrance to the cave. So when workers at the Guattari Hotel stumbled on it eight decades ago, “they found a situation that had been frozen in time, mummified to 50,000 years ago,” Professor Rolfo said.

The cave was studied until the early 1950s, but was not excavated again — and studied more comprehensively — until the last 20 months. That work has involved areas of the cave that were previously unexplored, including one cavity that regularly floods in the winter months.

The team of archaeologists, anthropologists, geologists and paleontologists also worked on the anterior area of the cave, unearthing burned bones, carved stones, and bones with cut marks, indicating that they had been hunted.

“We found rich traces of Neanderthal life there,” Professor Rolfo said.

Angelo Guattari, whose father owned the hotel in 1939 and was among the first to see the earlier Neanderthal skull, said that over time the cave had been mostly forgotten, unfortunately. Now, as the delegate for cultural heritage for the town of San Felice Circeo, he hopes the discoveries will lead the site to be opened to tourists.

The mayor, Giuseppe Schiboni, has applied for European Union funding to develop the town’s archaeological and anthropological pull. The hotel that the Guattari family once owned — since renamed “Neanderthal Hotel” — is up for sale. Mr. Schiboni said that he would love to buy it and install a European center on Neanderthal studies.

Once the site opens, possibly as soon as this year, visitors will be presented with a 10-minute virtual-reality video “and be catapulted into the cave” in its prehistoric guise, to help them better understand their surroundings, said Mr. Di Mario, who is coordinating the on-site research.

Neanderthals, said Mr. Rubini, the anthropologist, “were the uncontested lords of Eurasia for about 250,000 years.”

Whether humans will match that is an open question, he said.

“We don’t know if we will be — we’re still relatively young.”