Neanderthals and Humans Coexisted For So Much Longer Than We Thought

For thousands of years, Ilsenhöhle (or Ilse’s Cave in English) in Germany was somewhat of a paleolithic hidey-hole for animals like hibernating bears and cave hyenas, who were present in Europe for about a million years. The cave, which is nestled directly below a castle built from the same rock formation, was also an occasional safe haven for our modern human ancestors migrating in waves to Europe at least 46,000 years ago.

But Ilsenhöhle isn’t just a prehistoric sanctuary; for scientists today, its stratified layers are a time capsule now revealing an unprecedented overlap in the timelines of anatomically modern humans and another hominid ancestor: Neanderthals.

In a paper published Wednesday in the journal Nature, an archaeological analysis of skeletal remains excavated from the cave between 2016 and 2022 places our modern human ancestors north of the Alps at the earliest 45,000 years ago. That means that before the Neanderthals went extinct around 40,000 years ago, ancient and modern humans in that region co-existed for some thousands of years.

The paper is accompanied by two other studies conducted by the same research group, one figuring out how these early humans adapted to the harsh cold of Europe at the time and the other characterizing the ecology these individuals encountered along with their subsistence and diet.

“This fundamentally changes our previous knowledge about this time period: Homo sapiens reached northwestern Europe long before Neanderthal disappearance in southwestern Europe,” Jean-Jaques Hublin, the paper’s senior author and an emeritus director at the Max Planck Institute for Evolutionary Anthropology in Germany, said in a press release.

Unexpected human fossils

It’s no secret that modern humans and Neanderthals interacted with each other. Most of us carry remnants of Neanderthal DNA — around one to four percent in people of European or Asian background —which is a direct result of the two groups bumping uglies. (Our ancestors also got busy with other archaic humans.)

Scientists have sought to better understand the timeline of Neanderthal and human existence, especially with regard to stone tool technology, which was a motivation behind the new paper.

Around 45,000 years ago, there was a turning point in prehistory called the Middle to Upper Paleolithic transition, where we have the disappearance of the last Neanderthals and the arrival of Homo sapiens. A new type of stone tool emerged at this transition, known as the Lincombian-Ranisian-Jerzmanowician (or LRJ) technocomplex, characterized by its leaf-like shape. These tools have been found across northwestern Europe, spanning from Wales in the UK to Poland. Such tools were previously found in Ilsenhöhle, but who exactly their makers were — whether Neanderthals or humans — wasn’t quite clear.

In 2016, Hublin of the Max Planck Institute and a group of archaeologists and other scientists re-excavated Ilsenhöhle to hopefully get some answers. Digging meters down to the deeper layers of the cave where LRJ tools had been found, the researchers came across an unexpected find: human fossils.

“This came as a huge surprise, as no human fossils were known from the LRJ before, and was a reward for the hard work at the site,” Marcel Weiss, a researcher at the Max Planck Institute for Evolutionary Anthropology who co-authored the paper, said in the press release.

After confirming the bits of bone were indeed human by analyzing bone proteins, all 13 human skeletal remains were radiocarbon-dated to pinpoint when these individuals occupied the cave; this dating was also compared against radiocarbon dating of animal bones found within the vicinity and within different sedimentary layers.

“The evidence suggests that Homo sapiens were sporadically occupying the site from as early as 47,500 years ago,” Helen Fewlass, an archaeology scientist at the Francis Crick Institute, London, and formerly of the Max Planck Institute for Evolutionary Anthropology, who co-authored the paper, said in the press release.

The researchers also ran a genetic analysis of whatever mitochondrial DNA remained and sketched out a family tree. Most of the bits and pieces of bone shared the same mitochondrial DNA sequences, said Elena Zavala, a postdoctoral fellow at the University of California, Berkeley, and Max Planck Institute for Evolutionary Anthropology, who is the first author of the study.

“This indicates that the fragments belonged to the same individual or were maternal relatives, linking these new finds with the ones from decades ago," she said in the press release. “That raises some questions: Was this a single population? What could be the relationship here? But with mitochondrial DNA, that's only one side of the history. It's only the maternal side. We would need to have nuclear DNA to be able to start looking into this.”

Growing evidence

This study isn’t the first to suggest humans and Neanderthals were chilling together (or at least in some capacity) for much longer than previously thought. A 2022 paper published in the journal Science Advances also found humans in Western Europe likely co-existed with their thick-browed relatives as far back as 54,000 years ago based on bone fragments and stone tools excavated from a cave in southwestern France.

Hublin and his colleagues also published a paper in 2020 describing their findings that humans and Neanderthals had a time lap over maybe 8,000 years before the latter’s extinction. This was based on skeletal remains retrieved from a cave in Bulgaria that modern humans occupied at some point 46,000 years ago.

While Hublin said the new paper also points to modern humans, and not Neanderthals, as the creators of leaf-point tools, William Banks, an archaeologist at the French National Center for Scientific Research, says we shouldn’t be too quick to generalize the implications of these findings to other stone tool technologies elsewhere in the world.

“Another development is the recognition that Neanderthal groups were culturally complex, so we should not necessarily assume that all [Middle to Upper Paleolithic] transitional industries, because they differ from those of the preceding Middle Palaeolithic, must have been made by modern humans,” he wrote in an accompanying editorial. “For example, a lack of consensus surrounds the identity of groups (Neanderthal or modern human) associated with two transitional industries — the Châtelperronian in present-day France and northern Spain, and the Uluzzian in the Italian peninsula and immediately adjacent areas — clearly indicating the need for further objective investigation.”

What these new findings do dispel is the hypothesis that Neanderthals disappeared from northwestern Europe well before our modern ancestors arrived on the scene. What those last thousands of years looked like for Neanderthals has yet to be fully resolved. At least the Neanderthal genetic legacy continues to live on in us.