Planet of the Apes: by Enlarging the Brains of Apes Are Scientists Creating Worthy Opponents to Humans

News can be fascinating or frightening. Researchers have managed to “hack” into evolution by accelerating the transformation of the ape’s brain into a human-like brain thanks to a gene that increases the number of neural stem cells. The experiment was stopped for ethical reasons, but it still raises many questions about this kind of manipulation.

A thinking Ape

There are 95% of similarities between humans and chimpanzees. The human genome is therefore very similar to that of certain animals.

What if, thanks to genetic manipulation, apes became as intelligent as humans and competed with them as they did on the Planet of the Apes? The subject has fascinated scientists for years, and a new experiment brings us a little closer to Pierre Boule’s book, adapted for the cinema in 1968. German and Japanese researchers claim to have “hacked” into the evolution of the brain by increasing the volume of the neocortex in marmoset embryos.

The human brain and evolution

Seven million years separate the great apes from the first Homo sapiens. A slow development led to an increase in the brain size and changes in its structure, including an increase in the cerebral neocortex. The latter, the youngest part of the cerebral cortex during evolution, is about three times the size of our closest relative, the chimpanzee. It is at the center of cognitive functions such as logical thinking and language. One of the key questions for scientists is how the neocortex was able to become so large and give us our cognitive abilities.

A single small piece of DNA  makes all the difference

In the study published in the journal Science, Wieland Huttner and his colleagues at the Max Planck Institute for Cell Biology and Molecular Genetics (MPI-CBG) in Dresden have investigated the ARHGAP11B gene. The ARHGAP11B gene is the result of a mutation in the ARHGAP11A gene that occurred approximately 1.5 million years ago along the evolutionary line that led to today’s Neanderthals, Denisovans, and humans after the line of descent separated from that of the chimpanzee. This gene encodes a protein known for its ability to increase the production of neural stem cells.

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“The mutation in the ARHGAP11B gene from a single C to a G gene letter results in the loss of 55 nucleotides in the formation of the corresponding messenger RNA. This leads to a change in the transcription of the protein’s amino acids, explains Wieland Huttner. This mutation seems to have directly influenced human evolution,” he adds. By 2015, Huttner had succeeded in increasing the production of brain stem cells in mice, but with a “boosted” version of the gene. This time, German researchers joined forces with the Central Institute for Experimental Animals (CIEA) in Kawasaki and Keio University in Tokyo, pioneers in the creation of transgenic monkeys, to conduct an experiment with the normal version of the human gene in marmoset fetuses.

A larger, brain with more folding

The gene was implanted into Mykot embryos three to five days after ovulation. They then allowed the embryos to live to 101 days, 50 days before the normal date of birth. This allowed them to see three important developments in the development of the monkey brain:

  • An enlargement of the neocortex
  • A folded (crimped) configuration that in humans allows the brain to enlarge while fitting into the limited volume of the skull
  • An increase in the number of neural progenitor cells, particularly upper layer cells, which play a fundamental role in brain development in primates

Draconian ethical precautions

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From here to the creation of monkeys that are so intelligent and competitive to humans, many hurdles have to still be overcome. However, to avoid any controversy, the researchers have taken all ethical precautions. It is not a question of working on apes or chimpanzees that are too close to humans, or of completing the birth of genetically modified apes. Wieland Huttner also hints at criticism of the Chinese experiment. “It would have been irresponsible to complete the birth of the marmosets because the behavioral changes caused by the alteration of the neocortex are not known,” says Huttner. So for the moment, we will not know whether these marmosets could have played chess with us.

References

Human-specific ARHGAP11B increases size and folding of primate neocortex in the fetal marmoset

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