I’m not really surprised that genetics influence intelligence. I always thought that to be a pretty standard view and the 50 percent figure you are citing doesn’t exactly startle me.
I’m not so sure how important those 50 percent are in this context, though. One question that I think is not answered by twin studies is how ‘hereditary’ intelligence is. (I’m certain that there exists a wealth of literature about just that topic, I’m too lazy to look for it right now.) Do two parents of average intelligence only have children with similarly average intelligence or is the range of intelligence of their children much wider? Then there is obviously the question how well wealth corresponds to intelligence in the first place.
I’m not so sure how important those 50 percent are in this context, though. One question that I think is not answered by twin studies is how ‘hereditary’ intelligence is. (I’m certain that there exists a wealth of literature about just that topic, I’m too lazy to look for it right now.) Do two parents of average intelligence only have children with similarly average intelligence or is the range of intelligence of their children much wider? Then there is obviously the question how well wealth corresponds to intelligence in the first place.