Today we all share a large and deep gene pool, but that was not always the case. From first Homo Sapiens until we left Africa that gene pool was small and shallow. Genetically they were a far more homogeneous group than us. If you add consanguinity (inbreeding) to the mix then they faced an existential risk. Yet DNA analysis suggests that even though they lived in small tribes, they were less inbred than modern populations.
Evolutionary success depends on parents finding unrelated mates for their offspring. Think for a moment of the math problem they faced, they had to exclude everyone closely related to themselves and they had to know the family tree of a potential mate.
Bastard was the name given to low status offspring of an unknown father and they would struggle to find a mate. This lasted right up until the widespread adoption of the pill in the 1960's. Because most people lived in small rural communities how could women know a bastard child was not fathered by their close male relative? Or the close male relative of the bastards mother? The taboo was so strong that even today women in isolated communities have encyclopedic knowledge of how everyone is inter-related.
I know nothing of math's and struggle to frame the question, but I will try. How many people do you have to know the recent family tree of to avoid inbreeding when living in small groups over many generations? You would also have to know the family tree for three generations of surrounding tribes with whom you exchange mates. How do you do that for the 10,000 + generations humanity was isolated on the African Continent? Other species susceptible to inbreeding risks use pheromones to regulate mating, we have lost the knack. The Dunbar number of 150 would not last more than a generation or so. Could someone please ask GPT?
Stone Age Homo Sapiens solved the problem, perhaps it is one of the reasons they evolved brains capable of consciousness and complex thoughts. Their brains were not just spare capacity they carried around awaiting us to find a use for it, that is not how evolution works.