Why is the human brain so large? Scientists Solve the Mystery Page all

KOMPAS.com – One of the most important characteristics that distinguish humans from primates is the enormous brain size.

A chimpanzee, for example, only has a brain volume of 400 cubic centimeters, while a gorilla is 500 cubic centimeters.

Compare with the human brain reaching 1,500 cubic centimeters as an adult, the human brain is three times the size of a chimpanzee and gorilla.

This difference has long been a mystery among researchers, as the brains of humans and developing primates are difficult to study in detail.

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However, recently a group of international research teams has begun to uncover it. They found gen which makes the human brain bigger than the brains of gorillas and chimpanzees.

If these genes were tampered with, the research team found that they could make the human brain grow to resemble that of an ape and vice versa.

Reporting from The Guardian, Thursday (25/3/2021); Dr Madelieine Lancaster from the Laboratory of Molecular Biology, Cambridge who was involved in the study said we saw differences in the behavior of cells at a very, very early stage that made the human brain grow bigger.

“We can explain all the differences in size (using these findings),” he said.

Lancaster and colleagues discovered this particular molecule after collecting human, gorilla and chimpanzee cells left over from medical tests or surgery.

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The research team then reprogrammed the cells to become cell punca and growing them into organoids, tiny lumps of brain tissue only a few millimeters wide.

After a few weeks, the human organoids were found to be the largest.

The researchers then examined further and found that the reason for this difference was nerve cells progenitor (neural progenitor cell) which makes up all the cells in the brain.

In humans, progenitor nerve cells undergo more division in the early stages of brain development, which makes the number of neurons in the cortex of the cerebrum of an adult human double that of that of gorillas and chimpanzees.

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Well, the gene that regulates progenitor nerve cell division is Zeb2. Zeb2 was found to burn more slowly in humans, so the progenitor nerve cells could divide over a longer duration.

The test results even showed that slowing down the Zeb2 flame on the gorilla organoid, could make it grow bigger. Conversely, turning on Zeb2 early allowed human organoids to grow to resemble apes.

The results of this research have been published in the journal Cell.

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