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A problem I've run into is the use of ultra massive beings due to the effects of the square-cube law which means that I cannot within the current laws of physics have the world I envision. My world contains massive, island size ,tortoise-like creatures which walk through shallow coastal areas. These creatures are used as living space by sentient creatures with intelligence equal to humans or better.

However that does not work so what I propose instead is the having the tortoises normal size for a pet and the sentients proportionally sized. Is this possible? Are there any requirements?

Clarifying island size: The Isle of Wight.

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  • $\begingroup$ If your sentient creatures are smaller, you start running into brain size constraints. "Human or better" intelligence requires a pretty large brain. (But I love the idea of sentient animals living on the backs of really big tortoises!) $\endgroup$ – BrettFromLA Jan 13 '17 at 18:07
  • $\begingroup$ @BrettFromLA I was worried that this would be a problem. $\endgroup$ – Mendeleev Jan 13 '17 at 18:08
  • $\begingroup$ You don't really explain why giant turtles won't work. They just need someway to support their bulk. If they are in coastal seas already, part of that support will come from the water they are half way submerged in. $\endgroup$ – Green Jan 13 '17 at 18:09
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    $\begingroup$ @Mendeleev, I'm just interested in your explanation for why giant turtles won't work. Continents float on an "ocean of magma". Why couldn't giant turtles (if built correctly) not work on "oceans of water"? $\endgroup$ – Green Jan 13 '17 at 18:14
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    $\begingroup$ @Green The heavy upper bodies crushing the lower halves, if you're able to make it work please answer the other question. $\endgroup$ – Mendeleev Jan 13 '17 at 18:43
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Tiny sentience runs into the problem of brain size. While human medicine doesn't know everything about the brain, we know enough to identify regions that do certain tasks. Below a given threshold, there isn't enough space for all the regions, so with human physiology, it seems clear tiny humans would have to give up functionality.

But... do neurons have to be so large? Transistors of past decades are giant compared to the ones we use in computers today. Maybe neurons can be implemented smaller? (I am dodging the question of whether transistors are sufficient to replicate human intelligence... that's a topic for another day/forum.) Evolution has never to my knowledge had a reason to select for smaller neurons in humans. Maybe they can be made more space efficient without loss of functionality. That's an open question for science, so far as I know, so you're free to posit what you like.

Alternatively, if the braincase gets smaller, you might get different brain structure. Perhaps the limbic system stretches down the spine. Or the thyroid is near the gut. By distributing pieces, you might free up room in a tiny skull. From the outside, they'd still look human. Downside: injuries that to us are healable might not be to them. "Oh, a bolt through the arm. We can stop the blood, but that's where his autonomic systems are controlled from. I'm afraid he forgot how to breathe." That sort of thing. The torso/skull's advantage is it gives us one "critical region" to protect, and we can afford loss of limbs. The more the limbs have critical infrastructure, the worse it gets.

So, yes, there are ways to have tiny sentients that seem human. Just don't look inside or expect human doctors to treat them!

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  • $\begingroup$ Well that is a great answer thank you, it gives a great plan, you may of overlooked the great care I took in not saying humans to allow for differences. $\endgroup$ – Mendeleev Jan 13 '17 at 21:22
  • $\begingroup$ Thanks. I wasn't sure if you were excluding humans or trying to be inclusive of a world with humans and other sentient beings, so I covered bases. :-) $\endgroup$ – SRM Jan 13 '17 at 21:47
  • $\begingroup$ Non neuron based life is tricky, because we have so little prior art to work from -- all known sentient animals are neuron based. But it does offer great potential in removing limiting factors that exist in our world today! $\endgroup$ – Cort Ammon Jan 13 '17 at 22:16
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    $\begingroup$ tiny neurons don't exist in humans but they do exist, fairy wasp have very small neurons, The entire animal is smaller than an amoeba. many neurons lack a nucleus and is more reminiscent of a fungus than a normal set of neurons. blogs.discovermagazine.com/notrocketscience/2011/11/30/… $\endgroup$ – John Jan 14 '17 at 0:28
  • $\begingroup$ @John Are those neurons able to functionally replicate what human neurons do? $\endgroup$ – SRM Jan 14 '17 at 1:49
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One thing that I would consider is that, usually, small mammalians tend to have a fast metabolism, hence, die more quickly than humans. If your story lasts for several decades, you might have to think about it.

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