The unspoken assumption here is that poor people , immigrants and other such economically backward groups are backward because of their low IQ and the reason for their low IQ is primarily genetic.
IQ is predominantly genetic but it's well known how poor nutrition and upbringing can stunt it. There's lots of potential problems with this argument.
There is some evidence that the higher than average IQ of Asheknazi Jews is because of inbreeding. I posted about it on HN but people are wary of discussing such a sensitive subject.
Even discounting the genetics argument , it can also be considered as some kind of an accidental breeding for IQ as wealthier jewish families tended to have more children.
http://www.pbs.org/wnet/nature/dogs-that-changed-the-world-s...
http://www.icatcare.org:8080/advice/cat-breeds/inherited-dis...