We're not sure why this happened. Even "when" is the subject of ongoing discussions. But at some point, for some reason, our brains were big.
There are many hypotheses about how we arrived here, but we need experiments on chimpanzees and human brains to find supporting evidence, which includes practical (not to mention ethical) challenges. So these scientists went and built their copy
"It's a science fiction experiment that could not have happened ten years ago," says Arnold Kriegstein, a cell biologist at the University of California, San Francisco.
The team created simple, biochemically active brain cells from chimpanzees and human stem cells and used them to identify hundreds of genetic differences that could help explain their unique qualities
We are not talking here either. Scientists took cells from eight chimpanzees and ten people and used them to create a population of 56 copies, providing an unprecedented opportunity to accurately measure.
Technically, the human and chimpanzee brains they have created in laboratory glasses are not fully developed wrinkled gray material found inside the primates skull.
They are organoids ̵
Although the line between the actual organ and the organ of the organ is fuzzy, it is clear that the neurological tissue of this culture cannot process such information as a real transaction.
The genetic and biochemical activity of these cultures is sufficient to allow experiments that are impossible for bona fide specimens.
Isolation of DNA and proteins from the brain taken from dead chimpanzees and by humans is close to the comparison of the final credits of two films. You can know the characters, but there is a lack of parcels.
Brain Organoids allow researchers to evaluate how genes are activated and biochemistry fluctuates, and comparison of the time of development of important cells and other structures
means that each species-specific change can be accurately selected
Scientists deconstructed their instances at different stages of development, allowing comparison of emerging cell types and activation of genetic programs at each stage.
All of them were compared with reference materials taken from the third group of primates – rhesus monkeys.
The contradictions between the genetic activity of human and chimpanzeous organoids provide a fertile basis for identifying important mutations of each species that could explain how "These chimpanzees organoids give us a window that is otherwise inaccessible to us, up to six million years of our evolution," says neurologist Alex Pollen.
The analysis revealed 261 human specific genetic changes; One particular change that matched their interest was the neuronal precursor.
A few years ago, the Kriegstein Laboratory identified the molecular properties of cells that cause most of the human bark neurons, called an external radial glucose cell. This time, the team showed how activity in these cells increased their participation in the growth pathway for people, emphasizing the fundamental shift that could help explain the branch of human evolution from our big monkey relatives.
"Being so close to wild chimpanzees made me ask questions about the evolution of our own species," says Pollen, who explored the evolution of fish next to a well-known chimpanzee of the Gombe Stream National Park.
"First of all, we needed a sequence of genomes, stem cells, and lonely RNA sequences to understand evolutionary programs that stimulate brain development in two species.
Regardless of the history of the abnormally increased brain and victims, it will be difficult. Organoids provide new ways to study such activities on an unprecedented scale, providing a basis for demonstrating how small our evolutionary past changes have led to major differences in our biology
This study was published in Cell .