If you are referring to hunters and gatherers, they rarely lived in nuclear families but instead extended family groups. They also socially impose the norm of egalitarianism and are in constant contact with each other. I suspect the original author saw these in direct conflict with sociopathy.
The family raise a child who is a psychopath. The child then does what psychopaths do, and the family are in an abusive relationship with the child.
The child can be charming to outsiders etc and can find partners to procreate with.
Can't spot why they would not survive well in the paleolithic.