Although chimpanzees are the closest relative of humans, our brains are still significantly bigger than these primates. It is believed that the human genome evolved to have changes that trigger a massive growth of the brain.

Now, researchers from Germany have found a gene that can only be found in humans and is responsible for making us more intelligent than other creatures. The gene, dubbed ARHGAP11B, is believed to have emerged after human ancestors and chimpanzees split off from the same evolutionary path over five million years ago paving way for the rapid expansion of the human brain.

The gene, which was described in the journal Science on Feb. 26, dramatically increased the number of brain cells present in the key regions of the brains and thus led to the rise of human intelligence. It is likewise found in modern day humans, the Neanderthals, the Denisovans but not in chimps.

"Expression ofARHGAP11B in embryonic mouse neocortex promotes basal progenitor generation and self-renewal, and can increase cortical plate area and induce gyrification. Hence, ARHGAP11B may have contributed to evolutionary expansion of human neocortex," study researcher Mario Florio, from the Max Planck Institute of Molecular Cell Biology and Genetics in Germany, and colleagues wrote.

Although the presence of ARHGAP11B is one of the things that set the humans apart from other creatures, there are other differences between the brains of humans and chimps.

A 2014 study published in the journal Neuron, for instance, has identified an area of the ventrolateral frontal cortex of the human brain, which is associated with cognition and language, as among the things the things that make us humans. This particular area, known as lateral frontal pole prefrontal cortex, has no equivalent in the brain of the monkey. Researchers also believe it is responsible for the human ability to engage in tasks that need decision-making, strategic planning and multitasking.

In another study, researchers conducted functional brain scans in humans and monkeys while they were at rest and watching movie to compare the two species' cortical brain networks. They found the monkeys to have one unique network that is active during movie watching while the humans were found to have two unique networks suggesting of brain structures that are distinct in humans and anatomically lacking in the monkeys.

"Our findings confirm the existence of networks where evolution has conserved both topology and function but also suggest that functions of structurally preserved networks can diverge over time and that novel, hence human-specific networks, have emerged during human evolution," the researchers wrote

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