I stumbled across this paper, found it to be pretty interesting and skimmed through it.
"As homeostasis explains the functions of only a limited number of rewards, the principal reason why particular stimuli, objects, events, situations, and activities are rewarding may be due to pleasure. This applies first of all to sex and to the primary homeostatic rewards of food and liquid and extends to money, taste, beauty, social encounters and nonmaterial, internally set, and intrinsic rewards. Pleasure, as the primary effect of rewards, drives the prime reward functions of learning, approach behavior, and decision making and provides the basis for hedonic theories of reward function. We are attracted by most rewards and exert intense efforts to obtain them, just because they are enjoyable"
What differentiates humans between animals is that we have an increased need to seek pleasure for the sake of pleasure and our nebulous definition of "pleasure," all related to our very unique dopamine systems that occurred from a chance mutation. This is the origination of Art, which I define as very broadly as any creative act for the sake of pleasure. The first man-ape that drummed a beat made Art, the first to draw shapes in mud made Art, or put on pieces of cloth or arrange food in a pleasing way. Humans aren't particularly special, we're just the first species to reach the Point of No Return, because the advancement of Art is exponential and being the first means we reaped our rewards. Our inventions and technologies can be said to originate from a loop between dopamine centers and being rewarded with material/social benefits while being able to capitulate on those past inventions and keep building on them. Art is the reason we have technology, language, humor, and aesthetics.
The double-sided sword of this Promethean fire is that humans need pleasure and meaning in ways different than animals and when they don't get it they either go mad or self-medicate to get their needed "Purpose" and fulfillment. It's basically spiritual miasma and the cause of nonchemical depression. Some humans want a shortcut to fulfillment and will trample, steal, and set up unfair systems to exploit the Art of others, this is the origination of evil.
Types came to be because we are all genetically wired so our Purpose is related to our ego. A SLI is coded to get a lot more dopamine from aesthetic pleasure and comfort than an LIE, so this becomes a self re-enforcing process that turn into neuro-structural comfort zones and an area of confidence which we term the "ego." So an SLI is more likely to be depressed if they can't receive or create Si than an LIE. An IEE does not get a lot of dopamine from Fe but they are still strong because they get dopamine from Fi, which requires Fe so they still develop the neural pathways for it as an unintended consequence.
The 8 elements are what definitively constitute the entirety of our perception of reality and the split between all 8 is because without it we would all be bad at nothing and good at nothing as well; we would have no personality and just be empty. As for where the 8 elements came to be before humans could even perceive it - that's where the science stops and as a spiritual person I say it's honestly just pure magic and about as answerable as a question like why the first Big Bang occurred. We are conscious avatars for the universe who are looking at ourselves in a mirror and all the universe wants is more evolution, more madness, more magic-at an ever faster pace.