Is there a specific size range for intelligent life under biological constraints, or could smart aliens be as much smaller than bugs or much larger than whales?

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I read a long time ago an essay by Asimov that described what elements could support life as a building block and why most elements cannot. I didn’t fully understand that at the time but it was interesting to see why carbon based makes sense and some other random element does not work.

Similarly, I wonder if under different planetary conditions, smart alien life (so not single cell life) can be very tiny or very large, or if there are biological constraints that would restrict that size range regardless of basic setup.

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Anonymous 0 Comments

I just watched a kurgstaad video on why elephants can be shrunk or they would die, it actually is really relevant to this question.

Brains are complex things that need to have the cells within working at a relatively high rate of activity. The problem with that is that it generates a LOT of heat, heat you can only get rid of through the surface of an object. But as something gets bigger, the volume increases much faster than the surface area, so this heat exchange gets smaller and smaller as you get bigger and bigger.

Elephants deal with this by running their cells at a significantly reduced rate of activity, so they don’t generate as much heat. They also have more efficient heat dissipation systems than smaller animals, but that only can help so much. And with a brain, a huge brain that only works at a reduced rate of activity is no better than a much smaller brain that works at full capacity.

Of course, this assumes that a huge brain doesn’t evolve ways around this, through active cooling, modular processes, or something else. But given what we know, it seems reasonable to assume that the kind of cognitive functions we associate with humans can only come in a particular size of brain.

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