By Chris Skeldon 
By studying fossilized skulls, scientists know that the size of the Neanderthal brain was the same, if not slightly larger, than the size of the brain of modern humans. However, researchers know little about the evolution of the Neanderthal brain because soft tissues do not hold up well in the fossil record.
A fascinating study recently emerged that revealed a possible difference that may have given modern humans, or Homo sapiens, a cognitive advantage over Neanderthals, the Stone Age hominids who lived in Europe and some parts of Asia before their extinction about 40,000 years ago.
Scientists at the Max Planck Institute for Molecular Cell Biology and Genetics in Dresden, Germany, say they have identified a genetic mutation that led to faster formation of neurons in the brain of Homo sapiens. The primitive variant of the gene in question, known as TKTL1, differs from the modern human variant by a single amino acid.
“We have identified a gene that contributes to making us human,” said study author Welland Huttner, professor and director emeritus at the institute.
When two copies of the gene were inserted into mouse embryos, the research team found that a modern human variant of the gene led to an increase in a specific type of cell that creates neurons in the neocortex region of the brain. The scientists also tested the two genetic variants in rodent embryos and lab-grown brain tissue made from human stem cells, called organoids, with similar results.
The team argued that this ability to produce more neurons likely gave Homo sapiens a cognitive advantage unrelated to overall brain size, suggesting that modern humans had “a clearer neocortex than ancient Neanderthals,” according to the study published in the journal Neanderthals. Science.
“This shows us that while we don’t know how many neurons the Neanderthal brain has, we can assume that modern humans have more neurons in the frontal lobe of the brain, where TKTL1 activity is higher than that of Neanderthals,” Huttner explains.
He added, “There has been debate about whether or not the frontal lobe of Neanderthals was as large as modern humans.”
“But that’s not important because (from this research) we know that modern humans should have more neurons in the frontal lobe and we think that’s an advantage when it comes to cognitive abilities.”
‘Premature’ discovery
Alison Muotri, professor and director of the Stem Cell Program and Archeology Center at the University of California, San Diego, was not involved in the research, but said that while animal experiments revealed a “significant difference” in neuronal production, the difference was more subtle in organelles.
“This has only been done on one cell line, and since we have such a huge diversity with the organelles protocol in the brain, it would be ideal to repeat the experiments with a second cell line,” he said.
It’s also possible that the ancient version of the TKTL1 gene was not unique to Neanderthals, Muotri noted. Most genomic databases have focused on Western Europe, and it is possible that humans in other parts of the world shared the Neanderthal version of that gene.
“I think it’s too early to suggest differences between Neanderthals and modern human cognition,” he said.
Recent archaeological finds have indicated that Neanderthals were more complex than popular culture images (of animal cavemen) suggest. Our ancient relatives knew how to survive in cold and hot climates and used complex tools. They also made spinning, swimming, and created art.
Study co-author and geneticist Svante Pääbo, director of the Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany, pioneered efforts to extract, sequence and analyze ancient DNA from Neanderthal bones.
Their work led to the discovery in 2010 that early humans mixed with Neanderthals. Scientists later compared the Neanderthal genome to the genetic records of living humans today to see how our genes overlap and differ: TKTL1 is just one of dozens of specific genetic variations, and some genes in common could have implications for human health.