Less fun thought: there's an evolutionary bottleneck which prevents further progress, because the cost/benefit tradeoffs don't favour increasing intelligence much beyond the minimum.
So most planet-spanning civilisations go extinct, because the competitive patterns of behaviour which drive expansion are too dumb to scale to true planet-spanning sentience and self-awareness.
Intelligence is ability to predict (and hence plan), but predictability itself is limited by chaos, so maybe in the end that is the limiting factor.
It's easy to imagine a more capable intelligence than our own due to having many more senses, maybe better memory than ourselves, better algorithms for pattern detection and prediction, but by definition you can't be more intelligent than the fundamental predictability of the world in which you are part.
> predictability itself is limited by chaos, so maybe in the end that is the limiting factor
I feel much of humanity's effectiveness comes from ablating the complexity of the world to make it more predictable and easier to plan around. Basically, we have certain physical capabilities that can be leveraged to "reorganize" the ecosystem in such a way that it becomes more easily exploitable. That's the main trick. But that's circumstantial and I can't help but think that it's going to revert to the mean at some point.
That's because in spite of what we might intuit, the ceiling of non-intelligence is probably higher than the ceiling of intelligence. Intelligence involves matching an intent to an effective plan to execute that intent. It's a pretty specific kind of system and therefore a pretty small section of the solution space. In some situations it's going to be very effective, but what are the odds that the most effective resource consumption machines would happen to be organized just like that?
Sounds kind of like the synopsis of the Three Body Problem.
I seriously doubt it, honestly, since humans have anatomical limitations keeping their heads from getting bigger quickly. We have to be able to fit through the birth canal.
Perfectly ordinary terrestrial mammals like elephants have much, much larger skulls at birth than humans, so it’s clearly a matter of tradeoffs not an absolute limit.
Oh of course, but evolution has to work with what it’s got. Humans happened to fit a niche where they might benefit from more intelligence, elephants don’t seemingly fit such a niche.
> We have to be able to fit through the birth canal.
Or at least we used to, before the c-section was invented.
Indeed, but it hasn’t been around for long enough. We might evolve into birth by c-section, if we assume that humans won’t alter themselves dramatically by technological means over hundreds of thousands of years.