Neanderthals have long been portrayed as our less intelligent, cruder cousins. And now research has revealed striking differences in brain development between modern humans and Neanderthals.
The research involved inserting a Neanderthal brain gene from human stem cells into lab-grown mice, ferrets, and “mini-brain” structures called organoids. The experiments showed that the Neanderthal version of the gene was linked to a slower creation of neurons in the brain’s cortex during development, which scientists say could explain superior cognitive abilities in modern humans.
“Making more neurons lays the foundation for higher cognitive function,” said Wieland Huttner, who led the study at the Max-Planck-Institute of Molecular Cell Biology and Genetics. We think it’s compelling evidence.”
Modern humans and Neanderthals split into separate lineages about 400,000 years ago, when our ancestors remained in Africa and Neanderthals moved further north to Europe. About 60,000 years ago, the mass exodus of modern humans from Africa brought the two species face-to-face once again and integrated with each other. Today, modern humans of non-African descent carry 1-4% Neanderthal DNA. But 30,000 years ago, our ancient cousins disappeared as a separate species, and the question of how we outlived the Neanderthals remained a mystery.
Professor Laurent Nguyen of the University of Liège, who was not involved in the latest research, said: “The concrete fact is that wherever homo sapiens went, they would compete with other species there. It’s kind of weird,” says Professor Laurent Nguyen. “They were in the wild and would have adapted to their environment, including pathogens. The real question is why we’re able to outrun them.”
Some argue that our ancestors had an intellectual superiority, but until recently there was no way to scientifically test this hypothesis. This has changed over the past decade, with scientists successfully sequencing Neanderthal DNA from a fossilized finger found in a Siberian cave, paving the way for new insights into how Neanderthal biology differed from ours.
The latest experiments focus on a gene called TKTL1, which is involved in neuronal production in the developing brain. The Neanderthal version of the gene differs from the human version by one letter. The scientists found that placing the Neanderthal variant in mice resulted in less neuron production, particularly in the frontal lobe of the brain, where most cognitive functions are located. The scientists also tested the gene’s effect in lab-grown tissues and ferrets, called organoids, that replicate the basic structures of the developing brain.
“This shows us that while we don’t know how many neurons the Neanderthal brain had, we can assume that modern humans had more neurons than Neanderthals did in the frontal lobe of the brain, where [the gene’s] activity was highest,” says study lead author Anneline Pinson.
Chris Stringer, head of human origins research at the Natural History Museum in London, described the work as pioneering and said it’s starting to address one of the fundamental puzzles of human evolution, why we are now the only ones left, despite all the human diversity in the past.
“So many different ideas were presented, better tools, better weapons, appropriate language, art and symbolism, better brains,” Stringer said. “Finally, this provides a clue as to why our brains outperformed those of Neanderthals.”
While more neurons indicate the brain’s basic information processing capacity, it doesn’t automatically mean a smarter type of person. The human brain contains about twice as many neurons as the brains of some chimpanzee species.
Nguyen said the latest study isn’t conclusive proof of modern humans’ superior intelligence, but shows that Neanderthals had significant differences in brain development.
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