In an effort to better understand the evolutionary shift which led to the expansion of the human brain which led to homo sapiens being able to form languages and engage in complex thoughts, scientists at the University of California San Francisco (UCSF) have grown primate brains in petri dishes.
“By birth, the human cortex is already twice as large as in the chimpanzee, so we need to go back much earlier into embryonic development to understand the events that drive this incredible growth,” said Arnold Kriegstein who is the founding director of the Eli and Edyth Broad Center of Regenerative Medicine and Stem Cell Research.
The UCSF team constructed simple, biochemically active brains from chimpanzee and human stem cells, and used these models to identify hundreds of genetic differences between the two brain-types.
“It’s a ‘science fiction’ experiment that couldn’t have happened ten years ago,” says Kriegstein.
Read more: Scientists grow brains in petri dishes
However, these brains are not the fully developed, wrinkly organs that would be found inside human and chimpanzee skulls. They are organoids — mixes of tissue that have self-arranged into a 3D structure to serve as a model of the actual organ. These models are not capable of processing information like actual brains, which is not the goal of this study. However, they do contain sufficient genetic and biochemical activity to allow for experiments that would not be possible on actual human and primate specimens.
The UCSF team took cells from eight chimpanzees and ten humans, and used them to generate a population of 56 specimens. The large scope of this data led to more precise measurements.
Specimens were also deconstructed at different stages of development, which allowed the researchers to compare different types of cells which were emerging and the genetic programs that were being activated at each step.
Commenting on the study, neurologist Alex Pollen said, “These chimpanzee organoids give us an otherwise inaccessible window to six million years of our evolution.”
The research has been published in the journal Cell.