I'd thought that by living indoors and in otherwise controlled environments that there's not really much evolutionary pressure in any particular direction. Higher intelligence isn't a specific requirement to have (many) children live healthy lives.
You don't have to die to be selected out of the gene pool, you just need to fail to reproduce. If intelligence contributes to wealth and wealth contributes to reproductive success, then there will be evolutionary pressure favouring intelligence (and any other genes that "come along for the ride" with it).