Neanderthals have long been portrayed as our dimwitted, boorish cousins. Now, without confirming the stereotype, groundbreaking research has uncovered striking differences in how modern humans develop their brains 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 showed that the Neanderthal version of the gene was linked to slower formation 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 Cells biology and genetics. “We believe this is the first compelling evidence that modern humans were cognitively better than Neanderthals.”
The modern man and Neanderthals split into separate lineages about 400,000 years ago, with our ancestors staying in Africa and the Neanderthals moving north into Europe. About 60,000 years ago, a mass migration of modern humans from Africa brought the two species face to face again and they interbred – modern humans of non-African descent carry 1-4% of Neanderthal DNA. 30,000 years ago, our ancient cousins were gone as a distinct species, and how we outperformed the Neanderthals has remained a mystery.
“One concrete fact is that wherever they went, Homo sapiens basically outperformed other species. It’s a bit strange,” said Prof Laurent Nguyen of the University of Liège, who was not involved in the latest research. “These men [Neanderthals] were in Europe long before us and would have been adapted to their environment, including pathogens. The big question is why could we beat them?”
Some argue that our ancestors had an intellectual advantage, but until recently there was no way to scientifically test this hypothesis. This changed in the last decade when scientists successfully sequenced Neanderthal DNA from a fossilized finger found in a Siberian cave, paving the way for new insights into how Neanderthal biology differs from our own.
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. When introduced into mice, scientists found that the Neanderthal variant led to the production of fewer neurons, particularly in the brain’s frontal lobe, where most cognitive functions are located. The scientists also tested the gene’s influence in ferrets and clumps of lab-grown tissues called organoids, which replicate the basic structures of the developing brain.
“This tells us that while 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 highest than in Neanderthals,” said Anneline Pinson, first author of the study.
Chris Stringer, head of human origins research at the Natural History Museum in London, described the work as “groundbreaking” and said it began to tackle one of the central mysteries of human evolution – why, given all the diversity of humans past, we are now the only ones left.
“Ideas have come and gone — better tools, better weapons, right language, art and imagery, better brains,” Stringer said. “Finally, this provides a clue as to why our brains may have surpassed those of Neanderthals.”
More neurons do not automatically mean a smarter type of person, but they do determine the basic computing power 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 conclusive proof of modern humans’ superior intellect, but does show that Neanderthals had significant differences in brain development. “It’s an exciting story,” he added.