Modern humans have a gene mutation that boosts the growth of neurons in the brain neocortex, a brain region associated with higher intelligence
PPS Copyright: PHILIPPE PSAILA/SCIENCE PHOTO LIBRARY
Modern humans have a mutation that boosts the growth of neurons in the neocortex, a brain region associated with higher intelligence. This is absent in more ancient humans like Neanderthals, so it is likely that it makes us cleverer, say the researchers who uncovered it.
“We can assume that it made us smarter,” says Anneline Pinson at the Max Planck Institute of Molecular Cell Biology and Genetics in Dresden, Germany.
“I would say so,” says her colleague Wieland Huttner. “But we cannot prove it.”
The mutation results in a single amino acid change in a protein called TKTL1. Previous studies have shown that this mutation is present in almost all people alive today, but not in more ancient humans, such as Neanderthals and Denisovans, or in other primates.
The TKTL1 protein is also known to be produced in the progenitor cells that give rise to the neocortex – the outer layer of the brain involved in conscious thought and language – suggesting that the mutation might have helped shape the brains of modern humans.
To find out what difference the mutation makes, Pinson, Huttner and their colleagues added the modern human TKTL1 protein to the brains of mouse and ferret embryos. They also grew brain organoids from human cells, some of which were gene edited to produce the older version of TKTL1.
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These studies show that the mutation increases the number of neocortex progenitor cells, called basal radial glia, which results in a higher number of neurons in the neocortex. The result would have been an increase in the size of the neocortex, or of the density of neurons within it, or both, says Huttner.
Studies of skulls suggest that the brains of modern humans and Neanderthals were similar in size, but shaped differently, with Neanderthals having more elongated brains. The researchers speculate that it is possible this difference in shape is due to the mutation.
So could people be made more intelligent by tweaking genes in a way that further increases the number of basal radial glia?
“I don’t know if we could,” says Pinson. Having more neurons isn’t always a good thing, she says.
Journal reference: Science, DOI: 10.1126/science.abl6422
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