The shape, not size, of our ancestors' brains may have helped them outlast Neanderthals

Credit: CC0 Public Domain

For more than 200,000 years, Neanderthals successfully occupied the cold, dark forests and shores of Europe.

Then early humans came along.

Archaeological evidence suggests that human migrants from Africa arrived on the European continent around 40,000 years ago. About that same time, the Neanderthals all died off.

For decades, anthropologists have puzzled over what factors contributed to this rapid and total replacement of Neanderthals by their modern human cousins.

Now, a multi-disciplinary team including mechanical engineers, neuroscientists and physical anthropologists have provided a new clue to this mystery by creating the first digital reconstruction of four Neanderthal brains.

By comparing these brains with an average human brain, the authors suggest that different ways of processing information may have helped humans outcompete their hominid cousins.

The work was published Thursday in Scientific Reports.

To reconstruct a Neanderthal brain, the authors started by measuring the overall shape of the inside of four Neanderthal skulls.

Next, they created an "average" digital modern human brain and skull by combining MRI data of more than 1,000 modern humans.

Once they had these two measurements, they were able to use a computer program to warp the size and shape of the human brain to match the shape of the interior of the Neanderthals' skulls in a process called deformation.

This method is not entirely untested. The authors report that the same process has been shown to effectively re-create the structure of a bonobo brain by morphing a chimpanzee brain, and vice versa.

Using this technique, the researchers discovered that while the two types of brains were about the same size, there was a clear difference in shape.

In particular, the authors found that the cerebellum, a region of the brain that lies toward the lower back of our heads, was significantly larger in humans than in Neanderthals.

This part of the brain is associated with speech comprehension and production, working memory and , said Naomichi Ogihara, a mechanical engineer at Keio University in Yokohama, Japan, who worked on the study.

And in this region of the brain, size does matter.

The researchers demonstrated this by looking at data on brain size and abilities from 1,095 people that showed a clear relationship between the size of the cerebellum and language comprehension and cognitive flexibility.

The authors propose that because of their relatively small cerebellums, Neanderthals may have been less able to adapt to changes in the environment compared with the early human invaders, giving the humans a tremendous advantage.

However, the team's reconstructions also suggested Neanderthals did have at least one advantage over . The visual processing center of their brains, known as the occipital lobe, was larger than their counterparts.

Ogihara said the Neanderthals may have developed this adaptation in response to the low light levels in Europe compared with Africa, but it could have hindered them from expanding the cerebellum.

If that is indeed the case, this volumetric trade-off worked for a very long time—until it didn't.

Oh, and one more thing: Readers should remember, however, that this attempt to reconstruct the inside a fossil skull is new to the field, and perhaps could be improved upon in the future, Ogihara said.

"We would like to further elaborate our methodology by exchanging thoughts and ideas with researchers in the related fields working on evolution," he said.

He'd also like to use this method to reconstruct the brains of other hominins in the future.

Explore further

Scientists set eyes on Neanderthal 'brain'

More information: Takanori Kochiyama et al. Reconstructing the Neanderthal brain using computational anatomy, Scientific Reports (2018). DOI: 10.1038/s41598-018-24331-0
Journal information: Scientific Reports

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Apr 29, 2018
Intelligence is far from the most sought after traits when it comes to mating and natural selection. Almost every study I've ever encountered relating to our extant species outsurviving our extinct homo-cousins has placed our intelligence on the forefront of reasons for us being here and them going extinct. Neanderthals may very well have been orders of magnitude more intelligent than modern humans.

From reconstruction of Neanderthals I can tell what their downfall was. They were unattractive. The reason their species died out is so blatantly obvious. We were the more attractive species. Neanderthals chose modern humans over their own species as is evident by dna analysis. Neanderthals dna is found in our own gene pool. Given the opportunity, Neanderthals chose humans as partners which over time reduced their population. Also over time, the offspring of mixed couplings were also selected against.

Apr 29, 2018
I get a bit tired of hearing the old trope that the Neanderthals "died out" when DNA and skeletal studies support the notion that these top predators were simply absorbed into a much larger population of much more omnivorous H. Sap. peoples. This researcher's speculations about cognitive differences determined by brain shape are nothing more than speculation at this point.

Apr 29, 2018
In particular, the authors found that the cerebellum, a region of the brain that lies toward the lower back of our heads, was significantly larger in humans than in Neanderthals.

This part of the brain is associated with speech comprehension and production, working memory and cognitive flexibility, said Naomichi Ogihara, a mechanical engineer at Keio University in Yokohama, Japan, who worked on the study.

NO it isn't. The cerebellum is NOT "associated with speech comprehension ..., working memory and cognitive flexibility" (although its for some speach product). The cerelum, NOT the cerebellum, is "associated with speech comprehension ..., working memory and cognitive flexibility".
For anyone that might doubt my word for that, see for yourself by comparing;


with the wiki link for cerebellum.

I think this error really should urgently be edited out from this link because it is a significant blemish on this report.

Apr 29, 2018
kron, I just gotta compliment you for your skill as a comedic writer. Your comment had me laughing outloud! Though you did forget to suggest 'manscaping' a neanderthal.

Apr 29, 2018
I think it was the use of other body parts that caused cromags to prevail over Neanderthal.

Neanderthal has been living in temperate and subarctic regions for 300k years. And like any animal in similar environs, their reproduction became seasonal.

Humans who only mated at certain times during the year could not compete with tropicals who mated year round. They could not replace losses from conflict as fast. Their tribes were smaller and less able to defend themselves.

Tropical cromags quickly spread throughout a region and eliminated any competition for resources. Neanderthal were hunted for food. Their females were captured and incorporated.

The reason this obvious explanation is not widely accepted is that it runs counter to politically correct academies who cannot admit that because of their repro rate and inherent tribalism, humans have a very violent past.

And of course a very violent present.

Our repro rate has not changed since we left the tropics.

Apr 29, 2018
my misedit;

"...(although its for some speach product)..."

should be

"...(although its for some speech production)..."

Apr 29, 2018
How can they say the shape and not the size, when the cerebellum is known to contain many more cells than the rest of the brain? And yet convolutions are favored over a large cerebellum. More convolutions, more dense packing, more surface area, but even here I digress without an absolute ontology of configuration space.

If we look at human development the pruning of the prefrontal cortex stops, in favor of the visual cortex.
Relational theory can tell you there are constraints, albeit ambivalent (as neurons are know to be anthropic in 3-dimensions), to the ability of visualizable processes for synaptic cross-firing.
So where are we left, with an enactivist region's pruning being favored, after some template is capable of emulating the Markov-process, it was once bootsrapping. (Fodor)
Without knowing how Neanderthals or some generalization of hominid's brains prune and consume energy this is all unfalsifiable. Without our functionalism in their era, this is apples to oranges.

Apr 29, 2018
The real reason that Neanderthal got absorbed into the Cro-Magnon was not fitness, it was real estate. Retreating glaciers left lots of bogs, marshes, and shallow lakes. Building homes on stilts, and probably lifting one or two pathways at night, had two effects on population balance. New caves did not magically appear, so Cro-Magnon had lots more building room for villages and even smaller population centers than Neanderthal. Second, lots of time for young people, given darkness and privacy, to have sex. Besides I bet the hunters who used that extra time for sleep rather than guarding against predators were more successful.

Oh, and what should be obvious to anyone, supplementing diet with fishing gains many more calories for agriculture devoted to making nets than for other crops. Also helped with basket weaving and bags, which lead to both commerce and storage of food. This gave farmers time to develop spices, then staples into salable crops. Fish, spices, then grain.

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