As a rule all women breed (there are exceptions of course). In some societies high status males breed with multiple females and low status males have none. In most societies today marriage is 1:1, though there is lots of cheating but in general it means that some women will breed with low status males just for someone - thus all genes get carried on.
As I said I assume the powerful selected politically powerful mates for their girls, which might or not be intelligent as well. However it is possible that high status was high intelligence. The lower castes not following that.
Look, the above is all just barely possible. you will have to work with me here...