By studying fossilized skulls, scientists know that Neanderthal brain size was the same, if not slightly larger, than that of modern humans. However, researchers know little about Neanderthal brain development because soft tissue is poorly preserved 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 that lived in Europe and parts of Asia before they went extinct about 40,000 years ago. .
Scientists at the Max Planck Institute for Molecular Cell Biology and Genetics in Dresden, Germany, said they have identified a genetic mutation that caused faster creation of neurons in the Homo sapiens brain. The Neanderthal variant of the gene in question, known as TKTL1, differs from the modern human variant in one amino acid.
“We have identified the gene that makes us human,” said study author Wieland Huttner, professor and emeritus director of the institute.
When two versions of the gene were inserted into mouse embryos, the research team found that the modern human variant of the gene resulted in an increase in a particular type of cell that makes neurons in the neocortex region of the brain. The scientists also tested two variants of the gene in ferret 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 have “a more prominent neocortex than ancient Neanderthals,” according to a study published in the journal Science.
“This shows us that although we don’t know how many neurons were in the Neanderthal brain, we can assume that modern humans have more neurons in the frontal lobe of the brain, where TKTL1 activity is higher than in Neanderthals,” Hattner explained.
“There was a discussion about whether the frontal lobe of Neanderthals was as large as that of modern humans,” he added.
“But that doesn’t matter because (from this study) 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 ability.”
Alisson Muotri, professor and director of the UC San Diego Stem Cell Program and Archaealization Center, was not involved in the study, but said that while animal experiments revealed “drastic differences” in neuron production, the difference was more subtle in organoids.
“This has only been done in one cell line, and since we have tremendous variability with this brain organoid protocol, it would be ideal to repeat the experiments with a second cell line,” he said.
It’s also possible that an archaic version of the TKTL1 gene was not unique to Neanderthals, Muotri noted. Most genomic databases focus on Western Europe, and it is possible that human populations in other parts of the world may have a Neanderthal version of this gene.
“I think it’s rather premature to propose a distinction between Neanderthal and modern human cognition,” he said.
More recent archaeological discoveries have shown that Neanderthals were more complex than pop culture depictions (pictorial cavemen) suggest. Our ancient relatives knew how to survive in cold and hot climates and used sophisticated tools. They also wove yarn, swam and made art.
Co-author of the study and geneticist Svante Paabo, director of the Institute for Evolutionary Anthropology. Max Planck in Leipzig, Germany, made the first attempt to extract, sequence and analyze ancient DNA from Neanderthal bones.
Their work led to the discovery in 2010 that early humans intermingled with Neanderthals. Subsequently, scientists compared the Neanderthal genome with the genetic records of modern humans to see how our genes overlap and differ: TKTL1 is just one of dozens of identified genetic differences, and some of the common genes may have implications for human health.