I wonder how much is biology and how much is simply necessary functions of cognition? It's hard to tell since humans are unique in this regard.However what's neat is that biology designed us to have all 8.
This hypothesis is not one to which I lend as much credence. I think it's useful for describing the different "vibes" of Te/Fi and Ti/Fe, but I don't think it's "true" per se. It is necessarily a post hoc ergo propter hoc fallacy, assigning labels to behavior after observing the behavior.The Te/Fi is more suited to heirachal agrarian society while the Ti/Fe is more suited to hunter-gatherer.
So I wonder if we werent designed to be an adaptable populace. If we ended up settled, the Te/Fi folks would begin to outpopulate the Ti/Fe hunters-yet if things changed and we had to hunt again via a disturbance in equilibrium-the cognitive framework is in place to for the population to become more suited for the hunter gatherer Ti/Fe within a few generations.
Flexible cognitive evolution. neat-o.
That said, it's still a cool thought experiment, and it's interesting to see to what degree it is "sort of true." While each "kind of society" might express traits associated more with Te/Fi than Fe/Ti or vice versa, I strongly suspect that both have a strong role in either society, but that one role is more "visible" than the other.