This new research is the first to find how humans grow bigger brains, three times as many neurons. It is compared with the brains of gorillas and chimpanzees. This research discovered a main molecular switch that may help ape brain organoids grow like human organoids and in reverse.
This recent discovery was led by researchers from the Medical Research Council(MRC) Laboratory of Molecular Biology in Cambridge, UK.
How Humans Grow Bigger Brains
This study was published in the journal Cell, in which scientists compared brain organoids and 3D tissue growth from stem cells. They found that they were grown from the gorilla, chimpanzee, and human stem cells.
Like actual brains, the human brain organoids grew bigger than the other apes’ organoids.
Dr. Madeline Lancaster, who led the research, stated, “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. The most striking difference between other apes and us is just how incredibly big our brains are.”
In the beginning stages of brain development, neurons are created by stem cells known as neural progenitors. These progenitor cells are in a cylindrical shape that helps them to split into identical daughter cells in the same shape.
The more neural cells multiply in this stage, the later, the more neurons will be available. When cells are fully developed or grown, their multiplication will be decreased—that time, they elongate and form a shape like a stretched ice-cream cone.
Earlier, a study in mice showed that their neural progenitor cells developed into a conical shape, and their multiplication decreased within hours.
In this study, brain organoids helped scientists to find how this growth happens in humans, chimpanzees, and gorillas.
Scientists discovered that in chimpanzees and gorillas this transition consumes a long time, more than five days.
Human progenitors were slow in this transition and taking about seven days. They maintained their cylindrical shape for longer than other apes, During this period, they divide more frequently and make more cells.
The speed difference of transition from neural progenitors to neurons, human cells consume more time for multiplication. This could be the main reason for the three-time greater number of neurons in human brains than gorilla or chimpanzee brains.
Dr. Lancaster explained that “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.
Surprisingly, a simple evolutionary change in cell shape might have major effects on brain evolution. Dr. Lancaster further added that he feels like they have understood something fundamental about the questions that he had been curious about for a long time- what makes us human.
Scientists compared gene expression to figure out how the genetic mechanism drives these differences. They found that genes are switched on and off in human brain organoids compared to other apes’ brain organoids.
They discovered a difference in a gene known as ‘ZEEB2whichat was switched on in gorilla brain organoids in a short time compared to human organoids.
To examine the effects of the gene in gorilla progenitor cells, scientists delayed the ZEEB2 effects. This activity slowed the progenitor cells’ maturation, which helped gorilla brain organoids form more similar to humans that are slower and larger.
Contrarily, turning on the ZEEB2 gene(in a short period) in human progenitor cells encouraged premature transition in human organoids. As a result, they developed similarly to ape organoids.
Scientists recorded that organoids are a model or similar to all models that do not completely replicate real brains, particularly the mature brain’s function.
The study concludes that humans grow bigger brains than the other apes’ organoids. If you want to improve your brain power, you can do it in seven days.