The Neanderthals (Homo neanderthalensis) fascinate researchers and the general public alike. They remain central to debates about the nature of the genus Homo (the broad biological classification that humans and their relatives fall into). Neanderthals are also vital for understanding the uniqueness or otherwise of our species, Homo sapiens.
We shared an ancestor with the Neanderthals around 600,000 years ago. They evolved in Europe while we did so in Africa, before dispersing multiple times into Eurasia. The Neanderthals became extinct around 40,000 years ago. We populated the world and continue to flourish. Whether that different outcome is a consequence of differences in language and thought has been long debated.
But the evidence points to key differences in the brains of our species and those of Neanderthals that allowed modern humans (H. sapiens) to come up with abstract and complex ideas through metaphor - the ability to compare two unrelated things. For this to happen, our species had to diverge from the Neanderthals in our brain architecture.
Some experts interpret the skeletal and archaeological evidence as indicating profound differences. Others believe there were none. And some take the middle ground.
Disagreement is not surprising when trying to infer such intangibles from material remains such as bones and artefacts. The evidence is piecemeal and ambiguous, providing us with a complex puzzle for how, when and why language evolved. Fortunately, recent discoveries in archaeology and other disciplines have added several new pieces to this language puzzle, enabling a viable picture of the Neanderthal mind to emerge.
New anatomical evidence indicates the Neanderthals had vocal tracts and auditory pathways not significantly different to our own, indicating that, from an anatomical perspective, they were as capable as us at communicating through speech. The discovery of Neanderthal genes in our own species indicates multiple episodes of interbreeding, which implies effective inter-species communication and social relationships.
The discovery of Neanderthal wooden spears, and the use of resins for making tools from separate components, have also enhanced our views of their technical skills. Pendants made from bird talons and the likely use of feathers as body adornments are claimed as examples of symbolism, along with geometric engravings on stone and bone.
Cave painters?
The most striking claim is that Neanderthals made art, painting red pigment on cave walls in Spain. But several of these cave art claims remain problematic. The evidence for Neanderthal cave art is compromised by unresolved methodological issues and is unlikely to be correct, in my view.
Rapidly accumulating evidence for the pre-40,000-year presence of modern humans in Europe challenges the idea that Neanderthals made these geometric designs, or at least that they did so prior to the influence of the symbol-using modern humans. However well-crafted, a wooden spear is little more than a pointed stick, and evidence of technological progress is absent throughout the entirety of Neanderthal existence.
While the archaeological evidence remains contested, that from neuroscience and genetics provides a compelling case for linguistic and cognitive differences between H. neanderthalensis and H. sapiens.
A 3D digital reconstruction of the Neanderthal brain, created by deforming that of H. sapiens and fitting it into a cast of the brain (endocast) from a Neanderthal, indicates significant differences in structure. The Neanderthals had a relatively large occipital lobe, devoting more brain matter to visual processing and making less available for other tasks such as language.
They also had a relatively small and differently shaped cerebellum. This sub-cortical structure, which is packed with neurons, contributes to many tasks including language processing, speaking and fluency. The uniquely spherical shape of the modern human brain evolved after the first Homo sapiens had appeared at 300,000 years ago.
Some of the genetic mutations associated with that development are associated with neuronal development and how neurons are connected in the brain. The authors of a comprehensive study of all mutations known to be unique to H. sapiens (as of 2019) concluded that "modifications of a complex network in cognition or learning took place in modern human evolution".
Iconic words
While such evidence has been accumulating, our understanding of language has also changed. Three developments are of particular significance. First is the 2016 discovery via brain scanning that we store words, or rather the concepts we associate with words, throughout both brain hemispheres and in clusters, or semantic groups, of similar concepts in the brain. This is significant because, as we'll see, the way these clusters of ideas are connected - or not - was probably different between H. sapiens and Neanderthals.
Second is the recognition that iconic sounds - those that provide a sensory impression of the thing they represent - had provided the evolutionary bridge between ape-like calls of our common ancestor of 6 million years ago and the first words spoken by Homo - though we're not sure which species that was.
Iconic words remain pervasive in languages today, capturing aspects of the sound, size, movement and texture of the concept the word represents. This contrasts with words that are only arbitrarily related to the thing they refer to. For example, a canine can equally be called a dog, chien or hund - none of which provide a sensory impression of the animal.
Third, computer simulation models of language transmission between generations have shown that syntax - consistent rules for how words are ordered to generate meaning - can spontaneously emerge. This shift of emphasis from genetic encoding of syntax to spontaneous emergence suggests that both H.sapiens and Neanderthal language contained these rules.
The key difference
While it may be possible to join the puzzle pieces in several different ways, my long wrestle with the multi-disciplinary evidence has found only one solution. This begins with iconic words being spoken by the ancient human species Homo erectus around 1.6 million years ago.
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As these types of words were transmitted from generation to generation, arbitrary words and rules of syntax emerged, providing the early Neanderthals and H. sapiens with equivalent linguistic and cognitive capacities.
But these diverged as both species continued to evolve. The H. sapiens brain developed its spherical form with neural networks connecting what had been isolated semantic clusters of words. These remained isolated in the Neanderthal brain. So, while H. sapiens and Neanderthals had equivalent capacity for iconic words and syntax, they appear to have differed with respect to storing ideas in semantic clusters in the brain.
By linking up different clusters in the brain that are responsible for storing groups of concepts, our species gained the capacity to think and communicate using metaphor. This allowed modern humans to draw a line between widely different concepts and ideas.
This was arguably the most important of our cognitive tools, enabling us to come up with complex and abstract concepts. While iconic words and syntax were shared between H. sapiens and Neanderthals, metaphor transformed the language, thought and culture of our species, creating a deep divide with the Neanderthals. They went extinct, while we populated the world and continue to flourish.
Steven Mithen, Professor of Early Prehistory, University of Reading
