I think you're failing to account for how dramatically a relatively slight difference in intelligence within such a metric is liable to compound itself. A single really intelligent human can come up with insights in seconds that a thousand dimwitted humans can't come with in hours.

Well, by definition, their intelligence varies wildly according to the metric of making important discoveries. So surely you mean a relatively small difference in human biology. And this fact, while interesting, doesn't obviously say (to me) that the smart people have some kind of killer algorithm that the less intelligent folks lack... which is the only means by which an AGI could compound its intelligence. It just says that small biological variations create large intelligence variations.