Scientists have found that the variation in brain size among modern people often surpasses the differences observed between Neanderthals and early *Homo sapiens*, according to a study published in the *Proceedings of the National Academy of Sciences*. This finding suggests that traditional views on Neanderthal cognitive inferiority may need re-evaluation, explained cognitive scientist P. Thomas Schoenemann of Indiana University, a co-author of the research. The study utilizes MRI scans of living individuals to provide crucial context for ancient skull casts.
The long-standing debate about the cognitive capabilities of Neanderthals often starts with their skull shapes. A Neanderthal skull appears visibly different, longer and lower, compared to the rounder cranium of *Homo sapiens*. For decades, researchers have examined endocasts—natural or artificial molds of the interior of a skull—to infer brain characteristics.
These internal imprints provide a detailed, if indirect, record of the outer contours of ancient brains. For example, sediment filling the skull of a 2.8-million-year-old *Australopithecus africanus* child naturally formed such an endocast, preserving a glimpse into an ancient mind. However, these physical differences in skull shape, and the endocasts derived from them, may not tell the whole story about the brains they once housed.
Here is what the study actually says: many of those perceived differences fall well within the spectrum of variation seen in humans today. Previous investigations into Neanderthal neuroanatomy have fueled conflicting interpretations. A 2018 study, for instance, compared endocasts from four Neanderthals with four early *Homo sapiens*, meticulously measuring the volumes of thirteen key brain regions.
That research suggested that, despite possessing larger overall cranial capacities, Neanderthals generally had smaller cerebellums than *Homo sapiens*. The cerebellum, a small structure located at the back of the brain, plays essential roles in motor control, emotional regulation, and attention. While that observation was technically accurate for the small sample group, it presented an incomplete picture.
The headline is dramatic. The data is not, when placed in proper context. "The inferred differences were not put into the context of modern human populational variation in brain anatomy," P. Thomas Schoenemann and his colleagues wrote in their recent paper.
This lack of comparative data against the broad diversity of living humans meant any conclusions about Neanderthal uniqueness were potentially premature. Before you panic, read the methodology. To address this gap, Schoenemann's team embarked on a more comprehensive comparison.
They performed the same detailed size analysis using MRI scans from 400 modern individuals. This cohort included 200 U.S. residents of European descent and 200 ethnic Han Chinese individuals, all volunteers from the extensive Human Connectome Project. Their findings were compelling.
The differences in brain size between our species and Neanderthals were often equivalent to the differences *within* our own species. Specifically, for nine of the thirteen brain regions measured, Schoenemann and his team observed greater volumetric differences between certain modern humans than the earlier study had reported between Neanderthals and Pleistocene *Homo sapiens*. This is a significant reframe. "Our analysis shows that Neanderthal differences in brain and cognition would fit comfortably within the range of differences seen among modern humans," Schoenemann and his colleagues concluded.
This supports the idea that Neanderthals were not outliers. In essence, our species exhibits considerable diversity in brain structure, and the overall size and shape of Neanderthal brains fit squarely within this established human range. This perspective lends credibility to paleoanthropologists who argue against classifying Neanderthals and Denisovans as entirely separate species.
Furthermore, these size variations are generally too minor to exert any measurable impact on cognitive ability. Therefore, Neanderthals could easily have been our cognitive equals. This challenges a long-standing narrative.
Conventional wisdom frequently attributes *Homo sapiens*' evolutionary success to superior intelligence and "big brains." But what does that assertion truly mean? Decades of research have consistently shown that brain volume—whether considering the entire brain or specific regions—bears little to no correlation with an individual's performance on cognitive tests when compared to others within the same species. "Cognitive implications of neuroanatomical size differences are very weak in modern humans, when found at all," Schoenemann and his colleagues stated. When it comes to intelligence within a species, brain size simply does not matter as much as many assume.
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Defining "intelligence" itself remains a complex and somewhat elusive task. It is difficult to quantify precisely, yet scientists have tried for generations. Researchers studying cognition often break it down into specific areas: attention, inhibition, cognitive flexibility, speech production, speech comprehension, working memory, and episodic memory.
While some of these abilities are associated with particular brain sections, these relationships are frequently intricate and not solely dependent on size. The brain is more than its dimensions. When examining brain size and intelligence, the differences among human brains are relatively small compared to the vast differences between a human brain and, for instance, any other great ape brain.
Our closest relatives, chimpanzees, possess brains averaging just 400 cubic centimeters. The average adult human brain, by contrast, occupies approximately 1,350 cubic centimeters, with a typical range from about 1,100 to 1,500 cubic centimeters. This disparity is substantial.
Total brain volume is "empirically the best predictor of behavioral and cognitive abilities among primates," but this predictive power applies primarily when comparing *different* primate species. Within a single species, the differences are not sufficiently pronounced to be significant. When comparing vastly different species, like crows to dolphins, scientists factor in the encephalization quotient, which is the size of the brain relative to the overall animal size.
However, for primates, Schoenemann and his colleagues indicate that absolute brain size holds more relevance. For example, *Australopithecus afarensis*, an early hominin group that lived about 3.2 million years ago, had brains around 500 cubic centimeters. This substantial difference allows for reasonable inferences that their cognitive abilities were more akin to chimpanzees than to modern humans.
On the other hand, the average Neanderthal group exhibited a brain capacity consistent with them performing similarly on cognitive tests as their *Homo sapiens* contemporaries. This puts them in a different category entirely. What about the distinct skull shape, with Neanderthals having longer, lower craniums and *Homo sapiens* possessing higher, more rounded ones?
An earlier investigation suggested this morphological difference relates more to the shape of our faces than to the underlying structure of our brains. This indicates that external appearances can be misleading. The internal architecture might be more similar than previously thought.
Schoenemann and his colleagues' conclusion aligns well with other evidence regarding Neanderthal cognition: the artifacts they created and left behind. We know Neanderthals excelled in working memory and attention because they manufactured complex tools. These tools required sophisticated planning, sustained focus, and a mastery of skills that had to be taught, practiced, and refined over time.
Their capacity for symbolic, abstract thought is evidenced by the art they produced, including cave paintings and personal ornaments. Furthermore, their ability to meet and organize into large groups for cooperative big-game hunting implies developed language and social skills. These actions speak louder than skull dimensions.
Ultimately, the archaeological record provides a direct window into Neanderthal capabilities. We do not solely need to measure Neanderthal brain endocasts to understand their cognitive parity with us. They have already demonstrated it through their behaviors and creations.
This ongoing research helps us move past more than a century of ingrained bias against Neanderthals. It allows for a fuller appreciation of our extinct cousins and a deeper understanding of the intricate relationship we share with them in the grand tapestry of human evolution. Key Takeaways: - A new study indicates brain size variation within modern humans often exceeds differences between *Homo sapiens* and Neanderthals. - This challenges the notion that Neanderthals were cognitively inferior to early modern humans based on skull morphology. - Brain volume within a species shows little correlation with cognitive ability, contrary to popular belief. - Archaeological evidence of Neanderthal tool-making, art, and complex hunting supports their advanced cognitive capacities.
Why It Matters: This research reshapes our understanding of human evolution, moving away from a simplistic narrative where *Homo sapiens* outcompeted Neanderthals solely due to superior intellect. It suggests a more complex, nuanced relationship, potentially indicating that our species' success stemmed from factors other than inherent brainpower. For researchers, it underscores the importance of contextualizing ancient findings against the full spectrum of modern human biological diversity, moving beyond isolated comparisons.
The implications of this study extend beyond paleoanthropology, prompting a re-evaluation of how we interpret anatomical differences across human lineages. Future research will likely focus on more detailed comparisons of brain organization and connectivity, rather than just size, to uncover truly significant cognitive distinctions. Scientists will continue to explore genetic links and environmental pressures that might have shaped both Neanderthal and *Homo sapiens* development, offering a richer picture of our shared past.
Key Takeaways
— - A new study indicates brain size variation within modern humans often exceeds differences between *Homo sapiens* and Neanderthals.
— - This challenges the notion that Neanderthals were cognitively inferior to early modern humans based on skull morphology.
— - Brain volume within a species shows little correlation with cognitive ability, contrary to popular belief.
— - Archaeological evidence of Neanderthal tool-making, art, and complex hunting supports their advanced cognitive capacities.
Source: Ars Technica
