It turns out that most things in the universe don't have minds.
This statement would have provoked incredulity among many earlier cultures. "Animism" is the usual term. They thought that trees, rocks, streams, and hills all had spirits because, hey, why not?
I mean, those lumps of flesh known as "humans" contain thoughts, so why shouldn't the lumps of wood known as "trees"?
My muscles move at my will, and water flows through a river. Who's to say that the river doesn't have a will to move the water? The river overflows its banks, and floods my tribe's gathering-place - why not think that the river was angry, since it moved its parts to hurt us? It's what we would think when someone's fist hit our nose.
There is no obvious reason - no reason obvious to a hunter-gatherer - why this cannot be so. It only seems like a stupid mistake if you confuse weirdness with stupidity. Naturally the belief that rivers have animating spirits seems "weird" to us, since it is not a belief of our tribe. But there is nothing obviously stupid about thinking that great lumps of moving water have spirits, just like our own lumps of moving flesh.
If the idea were obviously stupid, no one would have believed it. Just like, for the longest time, nobody believed in the obviously stupid idea that the Earth moves while seeming motionless.
Is it obvious that trees can't think? Trees, let us not forget, are in fact our distant cousins. Go far enough back, and you have a common ancestor with your fern. If lumps of flesh can think, why not lumps of wood?
For it to be obvious that wood doesn't think, you have to belong to a culture with microscopes. Not just any microscopes, but really good microscopes.
Aristotle thought the brain was an organ for cooling the blood. (It's a good thing that what we believe about our brains has very little effect on their actual operation.)
Egyptians threw the brain away during the process of mummification.
Alcmaeon of Croton, a Pythagorean of the 5th century BCE, put his finger on the brain as the seat of intelligence, because he'd traced the optic nerve from the eye to the brain. Still, with the amount of evidence he had, it was only a guess.
When did the central role of the brain stop being a guess? I do not know enough history to answer this question, and probably there wasn't any sharp dividing line. Maybe we could put it at the point where someone traced the anatomy of the nerves, and discovered that severing a nervous connection to the brain blocked movement and sensation?
Even so, that is only a mysterious spirit moving through the nerves. Who's to say that wood and water, even if they lack the little threads found in human anatomy, might not carry the same mysterious spirit by different means?
I've spent some time online trying to track down the exact moment when someone noticed the vastly tangled internal structure of the brain's neurons, and said, "Hey, I bet all this giant tangle is doing complex information-processing!" I haven't had much luck. (It's not Camillo Golgi - the tangledness of the circuitry was known before Golgi.) Maybe there was never a watershed moment there, either.
But that discovery of that tangledness, and Charles Darwin's theory of natural selection, and the notion of cognition as computation, is where I would put the gradual beginning of anthropomorphism's descent into being obviously wrong.
It's the point where you can look at a tree, and say: "I don't see anything in the tree's biology that's doing complex information-processing. Nor do I see it in the behavior, and if it's hidden in a way that doesn't affect the tree's behavior, how would a selection pressure for such complex information-processing arise?"
It's the point where you can look at a river, and say, "Water doesn't contain patterns replicating with distant heredity and substantial variation subject to iterative selection, so how would a river come to have any pattern so complex and functionally optimized as a brain?"
It's the point where you can look at an atom, and say: "Anger may look simple, but it's not, and there's no room for it to fit in something as simple as an atom - not unless there are whole universes of subparticles inside quarks; and even then, since we've never seen any sign of atomic anger, it wouldn't have any effect on the high-level phenomena we know."
It's the point where you can look at a puppy, and say: "The puppy's parents may push it to the ground when it does something wrong, but that doesn't mean the puppy is doing moral reasoning. Our current theories of evolutionary psychology holds that moral reasoning arose as a response to more complex social challenges than that - in their full-fledged human form, our moral adaptations are the result of selection pressures over linguistic arguments about tribal politics."
It's the point where you can look at a rock, and say, "This lacks even the simple search trees embodied in a chess-playing program - where would it get the intentions to want to roll downhill, as Aristotle once thought?"
It is written:
Zhuangzi and Huizi were strolling along the dam of the Hao Waterfall when Zhuangzi said, "See how the minnows come out and dart around where they please! That's what fish really enjoy!"
Huizi said, "You're not a fish — how do you know what fish enjoy?"
Zhuangzi said, "You're not I, so how do you know I don't know what fish enjoy?"
Now we know.