Intuitively, it makes sense that intelligence would persist in Nature, because for all animals, brain power is useful and therefore at a minimum shouldn’t hurt a species. That said, it’s not clear why in particular homosapiens have grown more intelligent over time. As a general matter, selection should explain it. For example, it’s generally accepted that some kind of apocalyptic event lead to the demise of the largest dinosaurs, presumably an asteroid hitting the Earth. This killed off the largest animals above ground, presumably because they needed more food to survive than the small ones, and a catastrophic event could of course limit the total amount of food available for all animals. Smaller animals could survive on less food, and then eventually get bigger once conditions improved, which seems to be roughly what happened. So we can plainly see the mechanics involved: the total food supply literally shrinks, which kills anything that needs too much food, and whether or not this is exactly what happened, it makes sense, mechanically. Now why on Earth would animals get more intelligent as a function of time?
I think the answer is the same: disaster. When disaster strikes, the ability to predict the behavior of your environment could mean the difference between life and death. Because reality is governed by physics and mathematics, disaster could again be responsible for the selection of intelligence. So it’s indirect in this view: disaster forces selection for mechanical intuition and mathematics, and both of those require intelligence. Just imagine starting a fire near a bunch of wolves, near a body of water. Now set that same fire near a bunch of monkeys. Do the same with a bunch of people. Only the stupidest people won’t realize that the water probably won’t set on fire, whereas the same is not true of the wolves, and might not be true of the monkeys. That’s all you need to have literally all animals replaced by humans, disaster, and further, that’s all you need to get rid of stupid people as well, which could explain why humans have generally become more intelligent as a function of time.
Keep in mind a UTM is equivalent to processing language, suggesting that once you speak a language, you have all the intelligence you need, as a technical matter, to do all of computable mathematics. This suggests that in some sense humanity peaked at the development of language, and I think this could explain the proliferation of Phoenician-like languages, all the way out to Mongolia, for the simple reason that the Phoenicians might have been the first people to develop a written language, of course taking into account the possibility of a prior group that was subject to disaster.
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