A benign bone tumor that afflicts modern-day humans has now been found in one of our ancestors: a Neanderthal more than 120,000 years old.

The discovery of a fibrous dysplasia in a Neanderthal rib is the earliest known bone tumor on record, predating other tumors by more than 100,000 years. The rib, recovered from a site in Krapina, Croatia, indicates that Neanderthals were susceptible to the same types of tumors modern-day humans get, despite living in a remarkably different environment.

"They didn't have pesticides, but they probably were sleeping in caves with burning fires," says David Frayer, an anthropologist at the University of Kansas and the co-author of a new paper about the discovery. "They were probably inhaling a lot of smoke from the caves. So the air was not completely free of pollutants—but certainly, these Neanderthals weren't smoking cigarettes."

The tumor's journey from inside a bone over 120,000 years old to the pages of the journal PLOS ONE was a long one. It started in 1899, when a paleontologist named Dragutin Gorjanovic-Kramberger was digging by a cave near the Croatian village of Krapina. After coming upon a single human molar, a pile of animal bones, and a small stone tool, Gorjanovic-Kramberger and colleagues began an excavation at the site.

They soon realized they had stumbled upon the world's largest collection of Neanderthal artifacts.

Among the findings: animal bones, stone tools, and almost 900 fossilized Neanderthal remains dating back more than 120,000 years. In 1918, Gorjanovic-Kramberger described the bones:

"It is perfectly logical to assume that these Neanderthal men, who spent day and night in the open, eating a simple diet, had to be healthy and less prone to illnesses we have today. Accidents were therefore far more common in their struggle to survive and caused injury or even mutilation to the body."

But the Neanderthals also suffered from illness: conditions like severe arthritis, periodontitis, and tuberculosis, whose tell-tale signs have remained on the bones for more than 100,000 years.

Earliest Evidence

"There's lots of evidence of blunt-force trauma where these Neanderthals were hit in the head," says Janet Monge, the paper's lead author and a physical anthropologist at the University of Pennsylvania. "There's also evidence of an amputated forearm and arthritis. But this is the earliest evidence of a tumor."

Monge, who has been working with the Krapina bones for decades, was one of the first physical anthropologists to study x-rays of the bone collection. At first, she looked at plain films taken by Penn radiologist Morrie Kricun in the 1980s. But because the bones were so old, it was hard to see internal structures inside the bones themselves.

"They were really great radiographs, in terms of the way people go about diagnosing things, but we were getting basically black images of the bones," says Monge. "All of the internal structure of the bone was missing. And we thought there was a tumor there, but you don't want to say it's a possibility; you want to say it definitively."

So Monge and Kricun decided to try again, this time using a micro-CT scan machine, which slices an image into individually distinct cross-sections. In this case, the Neanderthal rib—which was about 30 mm (1.18 inches) long—was sliced into almost 500 distinct frames, which gave anthropologists and radiologists the ability to look at the bone piece by piece.

"We were able to refine all of the small detail going micron by micron," says Monge. "It also gave us the ability to remodel missing areas of the bone."

What the bone showed was that at least one Neanderthal suffered from a fibrous dysplasia, a benign tumor characterized by areas of abnormal growth in one or several bones.