Big brain evolution: compring chimp and brain organoids (Evolution)

by David Turell @, Friday, February 08, 2019, 19:16 (625 days ago) @ David Turell

By growing chimp and brain cultured organoids there are no ethical problems in doing gene comparisons to look at big brain evolution from the earlier primates:

"At some point during human evolution, a handful of genetic changes triggered a dramatic threefold expansion of the brain's neocortex, the wrinkly outermost layer of brain tissue responsible for everything from language to self-awareness to abstract thought. Identifying what drove this evolutionary shift is fundamental to understanding what makes us human, but has been particularly challenging for scientists because of ethical prohibitions against studying the developing brains of our closest living relative, the chimpanzee, in the lab. (my bold)

"'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, MD, Ph.D.

"In a study published February 7, 2019, in Cell, Kriegstein and collaborators have gotten around this impasse by creating chimpanzee brain "organoids"—small clusters of brain cells grown from stem cells in a laboratory dish that mimic the development and organization of full-size brains.


"By looking for differences in gene activity between human organoids and chimp organoids (as well as reference tissue from another primate, the rhesus macaque monkey) Bhaduri identified several hundred genetic changes unique to the human lineage that could help explain the evolutionary origins of the distinctly human brain. (my bold)

"For instance, Bhaduri discovered that neural precursor cells called outer radial glia (oRG)—originally discovered by the Kriegstein lab—showed heightened activity of a key growth signaling network known as the mTOR pathway in human organoids.

The Kriegstein lab has been studying the potential role of oRGs in the expansion of the human cortex for nearly a decade, "so it was particularly exciting to discover a molecular pathway in these cells that appears to have been specifically targeted during evolution and may help explain their specialized role in generating the advanced human cortex," Bhaduri said.


"Pollen said. "But first we needed genomes, stem cells, and single-cell RNA sequencing to be able to understand the evolutionary programs that drive brain development in the two species. All of these things have since fallen into place, letting us address these long-standing questions more precisely than ever before.'"

Comment: Note my bolds. Several hundred new genes are not a handful as described in the first paragraph. Yes it is, as if compared to all the genes we have, but as cooperative beneficial new genes created to affect this change it is not a handful, and clearly shows how the result of the study is propagandized to make it sound simple. This change requires design and a designer. This is the sort of hyperbole that I find constantly. Since it was not apparent to readers from my previous entries, I'll be more careful to point it out. It is misleading.

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