Why human brain is so big? Scientists shed light on the reasons

Although the size of the brain is not proportional to the level of intelligence, the human brain is amazingly large when compared with other mammals and exceeds its size in relation to the body, according to a new study published on March 24. Led by researchers at the Medical Research Council (MRC) Laboratory of Molecular Biology in Cambridge, UK, the study was published in the medical journal Cell. It compared the human brain organoids, 3D tissues of the organ that grow from stem cells, with that of other species such as gorilla and chimpanzees. 

In their analysis of the early development of the human brain, scientists found that the human brain organoids grew more rapidly and a lot bigger than the Apes or gorillas, with three times more nerve cells. A researcher at the MRC Laboratory of Molecular Biology, the lead author of the study said in the research: "This provides some of the first insight into what is different about the developing human brain that sets us apart from our closest living relatives, the other great apes.” aHe added, “The most striking difference between us and other apes is just how incredibly big our brains are."

[Brain organoids. Image Credit: Cell]

Early stages of development holds secret

Researchers found that during the early stages of brain development, neurons are made by cylindrical-shaped stem cells termed Progenitors. These cells then go on to divide into daughter cells with identical shapes and multiply very rapidly, which leads to the creation of more neurons in the brain ultimately. After excessive multiplication of Progenitors cells, a phenomenon key for the brain’s growth, several brain organoids are formed. “

"We have found that a delayed change in the shape of cells in the early brain is enough to change the course of development, helping determine the numbers of neurons that are made,” Dr. Lancaster said in the study. He added, “It's remarkable that a relatively simple evolutionary change in cell shape could have major consequences in brain evolution.” 

[Progenitor cells. Image Credit: Cell]

You have an increase in the number of those cells, so once they switch to making the different brain cells, including neurons, you have more to start with, so you get an increase in the whole population of brain cells across the entire cortex,” researchers explained in the study. The human brain organoids expand profusely, growing larger in the human head than in the gorillas and chimpanzees. The transition time for the apes is longer, approximately 5 days which leads to lesser brain organoids, scientists found. 

(Image Credit: Unsplash)