Neanderthals have long been portrayed as our goofy, bully cousins. Now, groundbreaking research, while not confirming the stereotype, has revealed surprising differences in the brain development of modern humans and Neanderthals.
The study involved inserting a Neanderthal brain gene into mice, ferrets and “mini-brain” structures called organoids, grown in the lab from human stem cells. The experiments revealed that the Neanderthal version of the gene was linked to a slower creation of neurons in the cerebral 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 work at the Max-Planck Institute for Molecular Cell Biology and Genetics. “We believe this is the first convincing evidence that modern humans were cognitively better than Neanderthals.”
Modern humans and Neanderthals split into separate lineages about 400,000 years ago, with our ancestors remaining in Africa and Neanderthals moving into northern Europe. About 60,000 years ago, a mass migration of modern humans out of Africa brought the two species face to face once again and they interbred: modern humans of non-African heritage carry between 1 and 4% of Neanderthal DNA. By 30,000 years ago, however, our ancient cousins had disappeared as a distinct species, and the question of how we bested Neanderthals has remained a mystery.
“One concrete fact is that wherever homo sapiens went, they would basically compete with other species there. It’s a bit strange,” said Professor Laurent Nguyen of the University of Liège, who was not involved in the latest research. “These guys [Neanderthals] they were in Europe long before us and would have adapted to their environment, including pathogens. The big question is why we could beat them.”
Some argue that our ancestors had an intellectual advantage, but until recently there was no way to scientifically test the hypothesis. That changed in the last decade when scientists successfully sequenced Neanderthal DNA from a fossilized finger found in a Siberian cave, opening the way for new insights into how Neanderthal biology differed from our own. .
The latest experiments focus on a gene, called TKTL1, involved in neuronal production in the developing brain. The Neanderthal version of the gene differs by one letter from the human version. When inserted into mice, the scientists found that the Neanderthal variant led to the production of fewer neurons, particularly in the frontal lobe of the brain, where most cognitive functions reside. The scientists also tested the gene’s influence in ferrets and patches of lab-grown tissue, called organoids, which reproduce the basic structures of the developing brain.
“This shows us that although we don’t know how many neurons the Neanderthal brain had, we can assume that modern humans have more neurons in the frontal lobe of the brain, where [the gene’s] activity is higher than Neanderthals,” said Anneline Pinson, first author of the study.
Chris Stringer, head of human origins research at London’s Natural History Museum, described the work as “groundbreaking”, saying it began to address one of the central puzzles of human evolution: why, with all the human diversity of the past, now they are the only ones left.
“Ideas have come and gone: better tools, better weapons, proper language, art and symbolism, better brains,” Stringer said. “Finally, this provides a clue as to why our brains might have surpassed those of Neanderthals.”
More neurons does not automatically equal a smarter type of human being, although it does determine the basic computing capacity of the brain. The human brain contains about twice as many neurons as the brains of chimpanzees and bonobos.
Nguyen said the latest work is far from definitive proof of the superior intellect of modern humans, but it does show that Neanderthals had significant differences in brain development. “This is an exciting story,” he added.
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