Got to love the internet. You can get a free university education without even leaving your bed. Just listened to a nice discussion about IQ and genes (hat-tip to Steve Hsu):
Among the interesting points:
IQ is probably determined by as many as 10,000 genes, and each gene may only influence IQ by as little as a fifth or a tenth of a point.
Once they get a million high quality genotype-phenotype pairs, they will be able to create a useful formula estimating IQ from genes, though commenter chartreuse would argue that reaction norms would make this formula only useful in a narrow range of environments.
Steve Hsu imagines police looking at the DNA left at the crime scene and knowing the suspect was a 6’1″ Asian with a 160 IQ, at which point someone on the panel joked that Hsu was talking about himself.
Apparently height can already be predicted from DNA to some degree. Professor Manfred Kayser states:
We were able to predict extreme height, which is those in the upper 3 percent, with an accuracy of 0.75, where 0.5 is random and 1 is a perfect indicator.
I assume he means that if they find some DNA, his prediction of whether the person is extremely tall will be right 75% of the time?
Steve Hsu notes that about 16% of the variation in height can be traced to genes that have actually been identified which means that a formula predicting height from genes would correlate 0.4 with actual height.
0.4 is about the correlation between height and weight. In other words, scientists are now at the point that can predict someone’s height from their genes as well as they can predict their height from their weight.
As more height genes are discovered, that correlation could roughly double.
Also mentioned in the above video is DNA editing CRISPR, but this will have little relevance to IQ for a long time to come, because if 10,000 genes are linked to IQ, and each one only affects it by a tenth of a point or so, then knowing where to edit to get a noticeable effect is currently impossible, and potentially dangerous, because humans have only 20,000 genes, so each one has many functions.