The brain is perhaps the organ that most distinguishes humans from other primates. Its exceptional size, complexity and capabilities far exceed those of any other species on Earth.
However, humans share more than 95% of their genome with chimpanzees. Why such a difference in brain development arose under these conditions was determined by scientists from the University of California at Santa Barbara (USA).
Although the complexity of human neural pathways is unmatched in the animal kingdom, researchers suspect that our unique intelligence is not the result of this.
Scientists in the study examined how genes evolved in different types of human brain cells compared to chimpanzee genes.
They found that although our genes encode almost all the same proteins as other apes, many of our genes are much more productive than those of other primates, the paper states.
Each gene instructs the cell to produce a specific molecule, but it is not the DNA itself that does this. Information is transmitted to cellular machinery using a molecule called messenger RNA (mRNA). Researchers measure gene expression by observing the amount of mRNA produced by a particular gene.
It was previously known that humans have higher gene expression than chimpanzees, but the exact details of the process were hampered by the lack of development of relevant technologies. Now scientists have the opportunity to study cell nuclei one by one. This allows researchers to distinguish between cell types, and often even subtypes.
Yes, the brain is made up of many types of cells. Traditionally, scientists divide brain cells into two main types:
- neurons (transmit electrochemical signals, like copper wiring in a house);
- glial (perform most of the other functions, such as insulating wires, maintaining structure, and clearing debris). In humans, glial cells make up more than half of the brain cells, a much larger percentage than even in chimpanzees.
In the new study, scientists measured gene expression by looking at the amount of mRNA a particular gene produced in humans, chimpanzees and macaques. As a result:
- scientists recorded differences in expression of about 5-10% from 25 thousand people. genes in the study. In general, human cells had more genes that caused cells to increase mRNA production compared to chimpanzees;
- that’s a much higher percentage than researchers previously found when they couldn’t analyze by cell type. And this percentage increased to 12-15% when the authors began to look at cell subtypes.
We now see that individual cell types have their own evolutionary paths, becoming truly specialized, the researchers note.
Thus, among glial cells, oligodendrocytes showed the greatest differences in gene expression.
These cells create the insulation that coats the neurons, allowing their electrical signals to travel much faster and more efficiently—in earlier studies, scientists noted that humans have a higher ratio of precursor to mature oligodendrocytes than chimpanzees. This may be due to amazing neural plasticity and slow brain development.
The increased complexity of our neural network probably did not evolve on its own, the researchers emphasize. “She couldn’t have appeared on her own.” It could not have emerged unless all other cell types had also evolved to increase the diversity of neurons, their number, and the complexity of their networks.
Therefore, the researchers note, evolution is more than just changing genes.
Differential gene expression is how the human brain actually evolved, the scientists conclude.
Scientists have discovered an unexpected reason for the start of human evolution
Source: Racurs
I am David Wyatt, a professional writer and journalist for Buna Times. I specialize in the world section of news coverage, where I bring to light stories and issues that affect us globally. As a graduate of Journalism, I have always had the passion to spread knowledge through writing.