Scientists Enlarged a Monkey's Brain by Adding Human Genes

Have these scientists not seen Planet of the Apes?

There are at least nine movies warning scientists not to enlarge monkey brains, lest the simian species take over the world. At least that’s the plot of Planet of the Apes and all its remakes and sequels since 1968. 

But apparently, scientists have not seen this apocalyptic film. In an experiment that looked exactly like a Planet of the Apes situation, scientists succeeded in increasing the size of the primate’s brain by splicing it with human genes. 

In a study published in Science, researchers from Germany’s Max Planck Institute of Molecular Cell Biology and Genetics and Japan’s Central Institute for Experimental Animals bioengineered a human gene, ARHGAP11B, into the fetus of a marmoset monkey. 

Normal Monkey Brain (Left) and Monkey Brain Enlarged with Human Gene

Photo by Science.

The result was chilling: The monkey developed a larger neocortex—which has long been considered the newest part of the brain in terms of evolution. 


In humans, the neocortex makes up 75 percent of the mass of the brain, and is responsible for complex thought, language, and reason. 

“Evolutionary expansion of the human neocortex is linked to our cognitive abilities,” wrote the scientists in their paper. 

According to the authors of the study, the gene ARHGAP11B arose roughly five million years ago, and is suspected of being responsible for the enlargement of the human brain through evolution. 

The researchers confined their analyses only to marmoset fetuses, not the ones that were born. 

Nevertheless, the scientists revealed some astonishing results of their experiments. “The… neocortex was larger and its cortical place thicker than in normal marmosets, and in contrast to the smooth surface of the normal marmoset brain, exhibited surface folds.”

Surface folds or gyrification is a feature created by the folding of the cortex, the part of the human brain responsible for higher cognitive processes such as memories, language and consciousness. 

For the sake of ethics and humanity’s survival, the scientists did not pursue the experiment on born marmosets. They were afraid to proceed with the experiment on born marmosets because of “unforeseeable consequences” with regard to the monkey’s brain development.

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Mario Alvaro Limos
Features Editor-at-Large
Mario Alvaro Limos is features editor-at-large at Esquire Philippines, and heads the Lifestyle and Esports content of as its section editor. Email him at [email protected] and [email protected]
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