Human and Neanderthal brain differences have been revealed

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By studying fossilized skulls, scientists know that the brain size of a Neanderthal was slightly larger than that of a modern human. However, researchers know little about Neanderthal brain development because soft tissue is not well preserved in the fossil record.

Now, an interesting study published on September 8 has revealed what may have given modern humans, or Homo sapiens, a cognitive advantage over Neanderthals, the Stone Age hominins who lived in Europe and parts of Asia before disappearing around 40,000 years ago. .

Scientists from the Max Planck Institute in Dresden (Germany) say they have identified a genetic mutation that caused the brain of Homo sapiens to generate neurons more quickly. The Neanderthal variant of the gene in question, known as TKTL1, differs from the modern human variant by one amino acid.

“We have identified a gene that helps one become human,” said study author Wieland Huttner, professor and director emeritus of the institute.

When both versions of the gene were inserted into the embryos of mice, the research team found that the modern human variant of the gene increased a specific type of… cell that produces neurons in the neocortex region of the brain. The scientists also tested both gene variants in horseshoe embryos and lab-grown brain tissue from human stem cells called organoids, with similar results.

The team reasoned that this ability to produce more neurons gave Homo sapiens a cognitive edge unrelated to overall brain size, suggesting that modern humans have “more neocortex than ancient Neanderthals” to work with, according to the study, published in the journal Science. .

“This tells 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 TKTL1 activity is highest, than Neanderthals,” explains Huttner.

“Whether the Neanderthal frontal lobe was as large as that of modern humans has been debated,” he added.

“But we don’t need to care because we know (from this study) that modern humans must have had more neurons in the frontal lobe … and we think that’s an advantage for cognitive abilities.”

Alysson Muotri, professor and director of the Stem Cell Program and Archaeology Center at the University of California, San Diego, said that while the animal experiments revealed a “pretty dramatic difference” in neuron production, the difference was more subtle in the organoids. He was not involved in the research.

“This was only done in one cell line, and since we have a lot of flexibility with this brain organoid protocol, it would be ideal to repeat the experiments with a second cell line,” he said via email.

The archaic version of the TKTL1 gene may also not be unique to Neanderthals, Muotri noted. Most genomic databases have focused on Western Europeans, and it is possible that human populations elsewhere in the world share the Neanderthal version of this gene.

“I think it’s quite premature to suggest differences between Neanderthal and modern human knowledge,” he said.

Archaeological discoveries in recent years have suggested that Neanderthals were more sophisticated than pop culture depictions of savage cavemen might suggest. Our ancient relatives knew how to survive in cold and warm climates and used complex tools. They made flour, swam and even created art.

Study author and geneticist Svante Pääbo, director of the Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany, led efforts to extract, sequence and analyze ancient DNA from Neanderthal bones.

His work in 2010 found that early humans interbred with Neanderthals. The scientists then 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 genetic differences identified, and some of the shared genes may have implications for human health.