I have a theory that intelligence, consciousness, free will are very easy to evolve (we just haven't worked out how to do it yet - like many cellular processes). What is difficult is harnessing that free will to the evolutionary success of the organism.
The large brain is necessary as a harness, to control the intelligence, and enslave it to evolutionarily beneficial ends. Probably not just hardwired instincts, but also learns - probably, similar to animal intelligence.
Like a giant finite state machine, that prevents a turing machine from running certain programs that never halt. Of course, it can't catch all such programs, and a turing machine can transcend any such bound, but lowering the probability of running one is good enough.
Note that turing equivalence, the highest possible computational power, emerges from even the slightest complexity (apart from the infinite tape part).
Thus "intelligence" has appeared in countless individual animals: mammals, birds, spiders, perhaps plants too and bacteria (and is still so appearing), but it doesn't confer a survival advantage, so disappears. Many such creatures just sit there discerning patterns instead of surviving. Others do survive but by instinct, so the intelligence makes no difference.
The difficulty is putting freewill in the driver's seat.
Monkeys and many, many other animals already have the first two, and whether there is such a thing as "free will" hasn't even been settled for humans.
In fact it's pretty hard to prove an animal doesn't have consciousness, and we just keep and keep adding to the list of animals that have consciousness and experience human-like emotions. We humans really aren't so special in that regard.
The next level is a bit more interesting, which is the question of which animals are able to develop a theory of mind, for which you need both consciousness and some intelligence.
The large brain is necessary as a harness, to control the intelligence, and enslave it to evolutionarily beneficial ends. Probably not just hardwired instincts, but also learns - probably, similar to animal intelligence.
Like a giant finite state machine, that prevents a turing machine from running certain programs that never halt. Of course, it can't catch all such programs, and a turing machine can transcend any such bound, but lowering the probability of running one is good enough.
Note that turing equivalence, the highest possible computational power, emerges from even the slightest complexity (apart from the infinite tape part).
Thus "intelligence" has appeared in countless individual animals: mammals, birds, spiders, perhaps plants too and bacteria (and is still so appearing), but it doesn't confer a survival advantage, so disappears. Many such creatures just sit there discerning patterns instead of surviving. Others do survive but by instinct, so the intelligence makes no difference.
The difficulty is putting freewill in the driver's seat.