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| The human (left) and chimpanzee (right) brain organoids contain multiple types of neural stem cells (red and green) and mature brain cells (magenta and cyan), mimicking the development of real human and chimpanzee brains. (Scale bar 100 micrometers). Credit: Pollen and Kriegstein Labs / UCSF |
Here's another one of those examples of where scientists don't set out to prove evolution and refute creationism, but they do anyway, quite incidentally, just by showing the facts.
They do it because the facts support evolution and so refute creation and any other wack-a-doodle rival notions about the diversity of living organisms from common origins. In this case, researchers were trying to explain what happened in human evolution that led to the increase in our brain size. This increase led to the evolution of the ability to learn and reason, to communicate and use language, and eventually to evolve group ethics and social systems. The rest is history, as they say.
The team of researcher based at the Department of Neurology, University of California, San Francisco (UCSF), CA, USA and The Eli and Edythe Broad Center of Regeneration Medicine and Stem Cell Research, UCSF, San Francisco, CA, USA used cultures of stem brain cells derived from skin cells of macaques, chimpanzees and humans to produce cultures of grown brain tissue known as organoids. This enabled them to see the differences in the development of the brains of the three species.
The technique of producing pluripotent stem cells from skin cells is a relatively new technique which enables these organoids to be grown in a laboratory.
What they found is that there are just a handful of genetic differences between the brains of chimps and humans that triggered the increase in the size of the human brain's neocortex. More importantly, they identified molecular pathways on which evolution appears to have acted. For example, one of the team discovered a neural precursor cells called outer radial glia (oRG) which showed heightened activity of a key growth signaling network known as the mTOR pathway in human organoids.
These changes have evolved in humans over the 6 million years since humans and chimpanzees diverged.
So, the major difference between humans and chimpanzees has been shown to be due to a small number of changes, leading to molecular pathways that have then been available to natural selection, leading to further beneficial development.
And once again, the close evolutionary relationship between humans and chimpanzees has been confirmed by a team not looking to confirm it, but doing so anyway, simply by revealing the facts.
Regrettably, the full paper is behind a paywall but the abstract can be read here.
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