Early humans suffered frequent head injuries but often lived long enough for those injuries to heal. That’s the result of a study that analyzed twenty 350,000-year-old skulls from a cave in Spain. The study also found that recovery wasn’t inevitable—several of the individuals in the cave apparently died from violent blows to the head.

Welcome to the Pit of Bones

About 350,000 years ago, deep in a cave network in what is now northern Spain, the remains of at least 29 people somehow ended up at the bottom of a 13-meter-deep shaft. Paleoanthropologists have unearthed thousands of broken pieces of bone, which add up to the partial skeletons of at least 29 members of a hominin species called Homo heidelbergensis, which may have been a common ancestor of our species and Neanderthals.

The pit, called Sima de los Huesos, contains a mix of ages and genders. Paleoanthropologists are still debating whether the pit was a burial site or just a place where bones washed in with floodwaters.