Now, an intriguing study published September 8 has uncovered a possible difference that 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 they became extinct about 40,000 years ago.
Scientists at the Max Planck Institute of Molecular Cell Biology and Genetics in Dresden said they had identified a genetic mutation that triggered the faster formation of neurons in the Homo sapiens brain. 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 make us human,” says study author Wieland Huttner, professor and emeritus director of the institute.
When the two versions of the gene were inserted into mouse embryos, the research team found that the modern human variant of the gene led to an increase in a specific type of cell that produces neurons in the neocortex region of the brain. The scientists also tested the two gene variants in ferret embryos and lab-grown brain tissue 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 “have more neocortex to work with.” , than ancient Neanderthals,” according to the study, published in the journal Science.
“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 than Neanderthals in the frontal lobe of the brain, where TKTL1 activity is highest,” explains Huttner.
“There was some debate as to whether the frontal lobe of Neanderthals was as large as that of modern humans,” he added.
“But we don’t have to worry about that because we know (from this research) that modern humans must have had more neurons in the frontal lobe… and we think that’s an advantage for cognitive ability.”
Alysson Muotri, professor and director of the Stem Cell Program and Archealization Center at the University of California San Diego, said while the animal studies showed a “pretty dramatic difference” in neuron production, the difference in the organoids was more subtle. He was not involved in the investigation.
“This was only done in one cell line, and since we have a lot of variability with this protocol from brain organoids, it would be ideal to repeat the experiments with a second cell line,” he said via email.
It’s also possible that the archaic version of the TKTL1 gene isn’t unique to Neanderthals, Muotri noted. Most genome databases have focused on Western Europeans, and it’s possible that human populations in other parts of the world share the Neanderthal version of this gene.
“I think it’s pretty premature to suggest any differences between Neanderthal and modern human cognition,” he said.
Study co-author and geneticist Svante Pääbo, director of the Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany, pioneered the extraction, sequencing and analysis of ancient DNA from Neanderthal bones.