They may have arisen in Europe or the Middle East and spread more readily east and west due to human migrations, as opposed to south to Africa because of geographic barriers. Or, they could have arisen in Africa, and increased in frequency once early humans migrated out of Africa.
More Quotes from Bruce Lahn:
The jury is still out on what this means because we aren't entirely sure what these genes do. It's possible they just control size and shape of the brain, rather than cognition. But the data is pretty compelling that the brain is evolving.Bruce Lahn
In a very short period of time, this class of variants arose from a single copy to many copies. That implies that this must have happened because of positive selection.
Bruce Lahn
People like to think of modern human biology, and especially mental biology, as being the result of selections that took place 100,000 years ago. But our research shows that humans are still under selection, not just for things like disease resistance but
Bruce Lahn
I think a lot of people might consider humans to be at the pinnacle of evolutionary lineage -- that we have achieved an advanced state as a species, and we have basically become the end-game. But what we found indicates that the species -- particularly when it comes to the brain, which is perhaps our most defining feature -- is still evolving.
Bruce Lahn
The frequency of the gene increases because people who carry these genes are more fit and they have more kids. We think each gene conveys some sort of fitness advantage in brain biology. It could be an improved cognitive function or a personality trait. We're not sure. But we know whatever consequence they render is highly favored by selection.
Bruce Lahn
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