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?

Question

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.

In: 324

Answer 1

Brains are complex enough that you could easily have smaller *or* larger creatures with intelligence comparable to humans. There’s no biological reason why a creature the size of a small monkey or a creature the size of a whale couldn’t possess human intelligence.

That said, it’s unlikely for something the size of an insect to posses human intelligence because you can only make neurons *so* small and you need a certain number of them to create the necessary complexity for intelligence, because it’s not *just* about having a complex enough brain, it’s also about having the requisite organs and other support needed to furnish that brain with the nutrients and energy it needs. As a point of reference, your brain makes up about 20% of your daily calorie consumption, so it takes a lot of energy.