> the brain’s wiring and complexity also evolved, which in turn drove advances in language, culture, and technology

Fun thought: to the extent that it really happened this way, our intelligence is minimum viable for globe-spanning civilization (or whatever other accomplishment you want to index on). Not average, not median. Minimum viable.

I don't think this is exactly correct -- there is probably some critical mass / exponential takeoff dynamic that allowed us to get slightly above the minimum intelligence threshold before actually taking off -- but I still think we are closer to it than not.

I like this idea. I’ve thought of a similar idea at the other end of the limit. How much less intelligent could a species be and evolve to where we’re at? I don’t think much.

Once you reach a point where cultural inheritance is possible, things pop off at a scale much faster than evolution. Still, it’s interesting to think about a species where the time between agriculture and space flight is more like 100k or 1mm years than 10k. Similarly, a species with less natural intelligence than us but is more advanced because they got a 10mm year head start. Or, a species with more natural intelligence than us but is behind.

Your analogy makes me think of boiling water. There’s a phase shift where the environment changes suddenly (but not everywhere all at once). Water boils at 100C at sea level pressure. Our intelligence is the minimum for a global spanning civilization on our planet. What about an environment with different pressures?

It seems like an “easier” planet would require less intelligence and a “harder” planet would require more. This could be things like gravity, temperature, atmosphere, water versus land, and so on.

>It seems like an “easier” planet would require less intelligence and a “harder” planet would require more.

I'm not sure that would be the case if the Red Queen hypothesis is true. To bring up gaming nomenclature you're talking about player versus environment (PVE). In an environment that is easy you would expect everything to turn to biomass rather quickly, if there was some amount of different lifeforms so you didn't immediately end up with a monoculture the game would change from PVE to PVP. You don't have to worry about the environment, you have to worry about every other lifeform there. We see this a lot on Earth. Spines, poison, venom, camouflage, teeth, claws, they for both attack and protection in the other players of the life game.

In my eyes it would require far more intelligence on the easy planet in this case.

How about Argentine ants?

The word "civilization" is of course loaded. But I think the bigger questionable assumption is that intelligence is the limiting factor. Looking at the history that got us to having a globe-spanning civilization, the actual periods of expansion were often pretty awful for a lot of the people affected. Individual actors are often not aligned with building such a civilization, and a great deal of intelligence is spent on conflict and resisting the creation of the larger/more connected world.

Could a comparatively dumb species with different social behaviors, mating and genetic practices take over their planet simply by all actors actually cooperating? Suppose an alien species developed in a way that made horizontal gene transfer super common, and individuals carry material from most people they're ever met. Would they take over their planet really fast because as soon as you land on a new continent, everyone you meet is effectively immediately your sibling, and of course you'll all cooperate?

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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.

I feel like there’s also a maximum viable intelligence that’s compatible with reality. Beyond a certain point, the smarter people are, the higher the tendency for them to be messed up in some way.