They recreate the brain evolution that made Homo Sapiens smart

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A gene unique to humans increases the size of the brain in primates

The gene responsible for human intelligence implanted in primates increases the size of its cerebral cortex, allowing it to host more neurons

Researchers from Germany and Japan introduced an exclusively human gene into the marmosets of primate marmosets and made their brains develop more than those of monkeys of the same species.

The species chosen for the experiment is Callithrix jacchus, endemic in the forests of eastern Brazil, although the marmosets in this research were imported from Japan. They are primates that do not naturally carry the gene under investigation.

The pregnancy of this species lasts 152 days, but after the first 101 days, the researchers observed that fetuses that had received the gene showed greater development in the neocortex, the most evolved part of the cerebral cortex.

They also found that that part of the brain had more folds, allowing it to increase the surface to house more neurons. It also contained more neuron-producing cells.

Cognitive responsibility

The gene implanted in the fetuses of these marmosets only exists in humans and is responsible for our intelligence. It is called ARHGAP11B.

It appeared in humans 5 million years ago, after our ancestors evolutionarily separated from chimpanzees.

This gene has effectively contributed to the enlargement of the cerebral cortex of our species. It has also been implanted in the past in mice, achieving an expansion of the cortex’s ability to host new neurons.

This research has gone one step further because the gene has been implanted in a model directly related to humans, to observe its behavior.

Important difference

With one important difference: it has not been the same gene implanted in mice (and ferrets) in the past since this gene has undergone a significant evolution throughout its history.

The gene that mutated five million years ago to promote our brain development underwent a more recent mutation, around a million years ago, and is the one that exists today in our species.

In experiments with mice, the previous version of this gene was implanted, while marmosets were implanted with the gene that we currently have working for our brain evolution.

Evolutionary recreation

The effect that this gene has had on the brains of marmosets is equivalent to the recreation in a species related to us of the same evolution that occurred in the brains of the ancient Homo Sapiens.

The purpose of these researchers is to learn more about the origin of some human diseases related to the abnormal growth of the brain, which can cause disorders such as autism.

Observing how this gene behaves in the marmosets’ brains will help researchers devise therapies for the growth of stem cells to treat diseases such as Parkinson’s.

Ethical implications

The authors acknowledge that they have entered very delicate terrain for their ethical implications, since manipulation of the human brain should only be done for therapeutic purposes, and never to expand the brain capacity of people.

Its main result is particularly related to the certainty unequivocally obtained in this research: that ARHGAP11B is the most important gene known so far for the development of the human brain.

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