When Homo sapiens (the ancestors of modern humans) first appeared on Earth about 300,000 years ago, they were not the only primitive people to roam our planet. Our ancestors were one of about nine primitive human species alive at the time — and one of at least 21 that ever existed on our planet, although the exact number is still unknown. controversial in the scientific community.
And the next question that comes to the mind of scientists is why only Homo sapiens has survived to this day. After all, our relatives the Neanderthals had brains similar to our own, but they went extinct about 40,000 years ago.
“Neanderthals were in Europe long before us, and they certainly adapted to the environment and climate there before our ancestors, including pathogens. The big question is why. we can compete with them,” Laurent Nguyen, a neuroscientist at the University of Liège in Belgium, told the Guardian’s Hannah Devlin.
Over the years, scientists have suggested and refuted various answers, Chris Stringer, head of human origins research at London’s Natural History Museum, told the Guardian: Better tools, better weapons, the right language, better art and symbols, better brains are the keys to helping our ancestors win the battle for survival.”
Now, a new study published in the journal Science may provide the correct answer: a genetic mutation in Homo sapiens allowed our ancestors to develop more neurons in the neocortex brain — an area of the brain involved in cognitive function.
The modern human version of the gene – called TKTL1 – differs from the Neanderthal version only by one of its amino acid building blocks. This substitution is found in essentially all modern humans, but extinct archaea, Neanderthals, Denisovans, and other primates do not have this mutation.
Co-author Wieland Huttner, a neuroscientist at the Max Planck Institute for Genetics and Molecular Cell Biology, told the New York Times’ Carl Zimmer: “What we found is a gene that definitely contributes to the genesis of the organism.” so who we are”.
In the new study, the researchers injected both a Neanderthal version of TKTL1 and a human version into the brains of developing mice and ferrets. The results showed that animals with the Neanderthal gene produced fewer progenitor cells that gave rise to neurons than the rest.
Next, the team knocked out the TKTL1 gene in human fetal brain tissue. This has the same result: fewer progenitor cells. In one final experiment, they used brain organoids, or lab-grown mini brain structures created from human stem cells. When they inserted the Neanderthal version of the gene into these tissues, the same pattern occurred.
The finding is “really a breakthrough,” Brigitte Malgrange, a developmental neurobiologist at the University of Liège who was not involved in the study, told Science’s Rodrigo Pérez Ortega: single amino acids are really important and can lead to amazing consequences for the brain.”
Although having a brain with more neurons does not equate to higher intelligence, the findings seem to suggest a change in the brain’s neurotransmitter system, which may gave Homo sapiens a cognitive advantage, according to the Times.
This amino acid difference alone probably doesn’t explain what makes our brains unique, the researchers say. “I don’t think that’s the end of the story,” Nguyen told the Times. “I think more work is needed to understand what makes us who we are in terms of brain development.”
References: Guardian; New York Times; Times