Oh, bite me.
All Hand-to-Mouth clanns are democrats. It is a survival instinct - feed the family, no hoarding. Children eat first.
When It gets bigger than a village, is when the problems come in.
Having outed myself as a democrat, I have an interesting theory - what if, as with the mules discussed above, the female hybrids were sometimes fertile, but the males never were?
That would explain the whole thing.
Theory, you can trash it.
;’)
The mule fertility is always the female, I believe; but the offspring is usually (always?) donkey or horse, depending on the sire.