A human ancestor previously unknown to science lived alongside ancient humans and Neanderthals - and they all interbred

A human ancestor called Nesher Ramla homo occupied Israel and Arabia alongside humans at least 120,000 years ago, a new study says.

• Scientists uncovered a new species of human ancestor named the Nesher Ramla homo in a sinkhole.
• This ancestor lived between 140,000 and 120,000 years ago in Israel and Arabia alongside humans.
• New research suggests Nesher Ramla homo interbred with humans, as well as our Neanderthal cousins.
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The eastern Mediterranean coast was a crowded place 120,000 years ago.

By that time, Homo sapiens - anatomically modern humans - had migrated out of Africa and settled in modern-day Israel and Arabia. Meanwhile, Neanderthals - our genetic cousins - had started to thrive in Eurasia.

Now, new research reveals that a third human ancestor was hunting and gathering in the same landscape. Two studies published Thursday in the journal Science describe a previously unknown hominin called the Nesher Ramla homo. The group not only shared tools and technology with their neighbors, they also interbred.

"They lived together and interacted with another," Rachel Sarig, an anthropologist from Tel Aviv University and co-author of the new studies, told Insider.

Sarig and her colleagues uncovered a partial jaw bone, which they pieced together from 17 fragments like a puzzle, deep in a sinkhole at an Israeli site called Nesher Ramla - hence the ancestor's name. There were also chunks of skull and a tooth belonging to the same individual.

Notably, the human ancestor had no chin - a feature distinct to Homo sapiens - and a flatter, squatter head. Those features suggest Nesher Ramla was a more ancient species than the region's other occupants.

"It was some kind of pre-Neanderthal," Sarig said.

The team had expected the bones to belong to a modern human.

"Homo sapiens were the dominant population in the Levant" between 100,000 and 200,000 years ago, Sarig said. "We were very surprised when we started looking at the fossils, and it was clear right away that Nesher Ramla was not the same."

A sinkhole in the Judean Hills

The discovery was a decade in the making. In 2011, workers were expanding a limestone quarry in the Judean Hills - between Israel's Mediterranean coast and Jerusalem - when they found a huge sinkhole.

In sediment about 25 feet down, Sarig's team uncovered animal teeth and bones, flint stone tools, and the Nesher Ramla bones. They suspect the sinkhole was an ancient watering hole, where animals came to drink and our human ancestors gathered to butcher game.

The researchers calculated that the animal teeth and flint were between 120,000 and 140,000 years old, suggesting Nesher Ramla homo lived then, too. But Hila May, a co-author of the new studies, told Insider that it's possible this prehistoric human started occupying the area up to half a million years ago.

Typically, hominins that lived during the Middle Pleistocene era in Israel, as Nesher Ramla homo did, are classified as part of the species Homo heidelbergensis. These ancestors are characterized by their use of fire to make tools and cook. But the authors of the study chose not to put this new human in that species, since its anatomical features do not align closely.

Still, May said this ancestor had a very similar way of life to Neanderthals and Homo sapiens.

"They were hunter-gatherers living in small groups, hunting animals like rhinos, horses, and deer," she said, adding that Nesher Ramla were "not very different in their abilities from other groups."

Interbreeding among human ancestors

The new study suggests that once Neanderthals migrated to Europe about 100,000 years ago, the Nesher Ramla group played a key role in shaping what they looked like and how they lived.

The new discovery might also solve a genetic mystery. Previous research found that some Neanderthals from the Middle Pleistocene era have genes that come from Homo sapiens. But these modern humans didn't arrive in Europe until about 45,000 years ago - long after the Neanderthals.

So if Nesher Ramla interbred with both Neanderthals and modern humans in the Levant before Neanderthals expanded west, that could explain the migration of the genes.

"We needed some explanation how Homo genes got to Europe before Homo got there," May said.

And the three hominins did more than just interbreed - evidence from the sinkhole also suggests they shared tool-making technologies, using the same types of flint tools made in the same way.