File under my favorite category “things that creationists say can’t happen and end up do happening”. A recent research article has shown that an incomplete gene duplication is likely responsible for humans having larger and more effective brains.
ARHGAP11B is a gene that is an incomplete duplication of the gene ARHGAP11A. The P11A gene produces a GTPase, a member of a family of proteins that are involved in a variety of areas of the cell. The authors were looking for genes that were involved in the development of the human brain. Why was the cortex, the outer layer of the brain, larger in humans and other primates than in mice?
First they had to identify the stem cells that become cortical cells. They did this by using fluorescent tags to the stem cells to see which cells became which type of tissue. Then they examined the cells that made up the cortex to see which genes were active in the cortex forming cells.
There were 56 genes that were in humans, but not mice. Of those, ARHGAP11B, was the most active. As I mentioned, this gene is known to have formed from a gene duplication event (which neatly defeats all the creationist arguments regarding gene duplication). (And as soon as I find a copy of the reference I’ll post it.)
The interesting thing is that that gene only exists in humans, Denisovans, and Neandertals. This is a human specific gene duplication event.
But it gets even more interesting. The authors placed that gene into the mouse genome to see what would happen. Remember that this is an incomplete copy of a totally different gene.
The number of cortex stem cells doubled and their brains sometimes developed folds. These folds are not present in mice normally, but are present in primates. The gene also causes more stem cells that divide more frequently. Resulting in a larger than normal brain.
I’ll let the authors speak about the result that
emphasizes the likelihood that this gene was indeed important during mammalian evolution for the design of a new brain, bigger and more complex,
So, there we go an incomplete gene duplication results in thicker cortexes, with more folding. The authors clearly state that they think there are more genes waiting to be discovered, but this is a pretty astounding result.
It is very likely that a total accident is one of the reasons humans evolved into intelligent creatures.
