How single mutation may have led humans to become more intelligent than Neanderthals

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A new study suggests that a variation of a single protein in the brains of modern humans may be responsible for their improved cognitive abilities compared to Neanderthals.

The researchers assessed the effect of changes in a single amino acid building block that is associated with greater nerve cell production in the frontal lobe of the brain.

“Modern humans differ from apes and Neanderthals by this single amino acid change,” including scientists from the Max Planck Institute of Molecular Cell Biology and Genetics in Germany, say in the study published Thursday in the journal Science. science,

The protein, known as transketolase-like 1 (TKTL1), is involved in the production of basal radial glia of the brain, the workhorse that generates the frontal lobe during brain development – ​​a part of the brain that is responsible for many cognitive abilities. is important.

While the brains of Neanderthals and modern humans are similar in size, the researchers say “very little” is known about whether the brains of the two species may have differed in terms of their neuron production during evolution.

Specifically, they state that both modern humans and Neanderthals have a brain with a similarly sized neocortex – a brain region known to play a key role in sensory perception, emotion, and cognition. Whether this indicates an equal number of nerve cells in the neocortex remains unclear.

While previous studies have discovered a small number of proteins that differ between modern humans and our extinct relatives – Neanderthals and Denisovans – scientists say the significance of these differences to the development of the modern human brain is also unknown.

In the research, the scientists analyzed one of these proteins – TKTL1 – that presents a single amino acid change in essentially all modern humans compared to Neanderthals.

This protein is found in embryonic progenitor cells from which all neurons for more advanced cortex brain regions derive. Notably, TKTL1 levels are highest in progenitor cells of the frontal lobe of the developing brain.

In modern humans, TKTL1 contains the amino acid arginine at one sequence position, whereas in Neanderthal TKTL1 it contains the corresponding amino acid lysine at this position.

When scientists introduced either a modern human or a Neanderthal version of TKTL1 into the neocortex of mouse embryos, they found that a type of progenitor cells with the modern human version of TKTL1 thought to be the driving force for a larger brain.

This effect was not seen with the Neanderthal type of protein.

As a result, the researchers say that the brains of mouse embryos with modern human TKTL1 contain more neurons.

The scientists conducted another experiment using lab-grown mini-human and Neanderthal brains, where they replaced the arginine amino acid with the lysine characteristic of Neanderthal TKTL1 in modern human TKTL1.

“We found that TKTL1, with Neanderthal-type amino acids, produced fewer basal radial glial cells than the modern human-type and, consequently, fewer neurons as well,” said study co-author Anneline Pinson .

“This shows us that even though 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 highest, than in Neanderthals,” Dr. Pinson said.

Researchers suspect that modern human TKTL1 enhances the synthesis of certain membrane molecules needed to increase neuron production in the frontal lobe.

“This study implies that the production of neurons in the neocortex during embryonic development is higher in modern humans than in Neanderthals, particularly in the frontal lobe. It is tempting to speculate that this may have influenced modern human cognitive abilities involving the frontal lobe.” promoted,” said Weiland Hutner, another study author.

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