Brain expansion: Specific human gene found (Evolution)

by David Turell @, Thursday, June 18, 2020, 21:20 (19 days ago) @ David Turell

It has been tested in monkeys and enlarged their cortex:

"The expansion of the human brain during evolution, specifically of the neocortex, is linked to cognitive abilities such as reasoning and language. A certain gene called ARHGAP11B that is only found in humans triggers brain stem cells to form more stem cells, a prerequisite for a bigger brain. Past studies have shown that ARHGAP11B, when expressed in mice and ferrets to unphysiologically high levels, causes an expanded neocortex, but its relevance for primate evolution has been unclear.

"Researchers at the Max Planck Institute... now show that this human-specific gene, when expressed to physiological levels, causes an enlarged neocortex in the common marmoset, a New World monkey. This suggests that the ARHGAP11B gene may have caused neocortex expansion during human evolution.

"The human neocortex, the evolutionarily youngest part of the cerebral cortex, is about three times bigger than that of the closest human relatives, chimpanzees, and its folding into wrinkles increased during evolution to fit inside the restricted space of the skull. A key question for scientists is how the human neocortex became so big. In a 2015 study, the research group of Wieland Huttner, a founding director of the MPI-CBG, found that under the influence of the human-specific gene ARHGAP11B, mouse embryos produced many more neural progenitor cells and could even undergo folding of their normally unfolded neocortex. The results suggested that the gene ARHGAP11B plays a key role in the evolutionary expansion of the human neocortex.

"The human-specific gene ARHGAP11B arose through a partial duplication of the ubiquitous gene ARHGAP11A approximately five million years ago along the evolutionary lineage leading to Neanderthals, Denisovans, and present-day humans, and after this lineage had segregated from that leading to the chimpanzee. In a follow-up study in 2016, the research group of Wieland Huttner uncovered a surprising reason why the ARHGAP11B protein contains a sequence of 47 amino acids that is human-specific, not found in the ARHGAP11A protein, and essential for ARHGAP11B's ability to increase brain stem cells.

"Specifically, a single C-to-G base substitution found in the ARHGAP11B gene leads to the loss of 55 nucleotides from the ARHGAP11B messenger RNA, which causes a shift in the reading frame resulting in the human-specific, functionally critical 47 amino acid sequence. This base substitution probably happened much later than when this gene arose about 5 million years ago, anytime between 1.5 million and 500,000 years ago. Such point mutations are not rare, but in the case of ARHGAP11B its advantages of forming a bigger brain seem to have immediately influenced human evolution.


"However, it has been unclear until now if the human-specific gene ARHGAP11B would also cause an enlarged neocortex in non-human primates. (my bold)


"They generated transgenic common marmosets, a New World monkey, that expressed the human-specific gene ARHGAP11B, which they normally do not have, in the developing neocortex.


"Michael Heide explains: "We found indeed that the neocortex of the common marmoset brain was enlarged and the brain surface folded. Its cortical plate was also thicker than normal. Furthermore, we could see increased numbers of basal radial glia progenitors in the outer subventricular zone and increased numbers of upper-layer neurons, the neuron type that increases in primate evolution." The researchers had now functional evidence that ARHGAP11B causes an expansion of the primate neocortex."

Comment: We now know what genetic change occurred to push human brain enlargement over five million years ago. In my theory God made the genetic change. His mind knew what would happen. dhw will tell us the brain cells themselves made the change. How did the cells know what they were doing? Did God tell them what to do? Let's leave God out. Note my bold. The code does not tell anyone what will happen when applied. The scientists (with brains) had to put the gene in action to be sure how it might produce more cortex, and we still have no idea how genes produce their results. Now, put God in, as dhw does with his inventive mechanism, and what had to happen? A specific gene change of 47 bases to get the result. That required specific guidance, guidelines as I always insist upon.

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