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Old 12-18-2016, 10:29 PM
Chief Pedant Chief Pedant is offline
Join Date: Feb 2007
Posts: 6,970
Originally Posted by aldiboronti View Post
And I mean people in general not nonsensical stuff about races. Is it something physical, something to do with differences in the brain itself? It surely can't be environmental, too many dumb rich people and smart poor ones for that to be true. On the other hand it can't be genetic, geniuses rarely spawn geniuses and many a moron has sired a really intelligent kid.

So if it is some difference in the brain what exactly is it? Is it size, the bigger the brain the smarter you are? Or is it like the penis, it's not the size that matters it's what you do with it?

My own grey matter, such as it be, needs a little help with this one!
I am not sure why you dismiss "stuff about races" as "nonsensical." As a general rule, "races" reflect continent of recent origin for source pool genes, and of course the history of human migration means that the average frequency for all gene variants--including those related to neurologic function--vary among "races." For example, you would find a marked difference in the average frequency for MCPH1 Haplogroup D variant between (self assigned) whites and asians, and (self-assigned) blacks. This is because those self-assigned races tend to correlate with their continents of recent origin, and MCPH1 Haplogroup D only arose about 40,000 years ago. It has since achieved very high penetration in post-africa groups, but very little back diffusion into sub-saharan africa (perhaps with the exception of the horn) because of human migration patterns.

Anyway, the way to look at genes and brain function is to think of genes as providing a substrate upon which the environment acts. That substrate (nature) provides a ceiling beyond which the environment (nurture) cannot excel. You can't get a chimp to read and write worth a damn, and you can't get the Pedant to understand advanced math no matter how good the nurturing is. You can make either of us "smarter" with good nurturing. But only smarter than we would be with lousier nurturing; not smarter than our genetically-programmed ceiling.

We don't know nearly enough about genes and their interplay to identify which genetic combination is great. We do have some teasers. Here is an example that looks at processing speed. And every gene has a wide variety of variants each of which may affect intelligence, alone or in combination. For example, one study showed if you substitute a single instance of thymine for cytosine in the HMGA2 gene, you increase intelligence about 1%.