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A Glebsig (plural Glebsigi) is an intelligent alien species from the game Stellaris. They look like this:

enter image description here

Glebsigi can float in mid-air with their tentacles hanging below. Glebsigi manipulate things by using their tentacles much like human fingers (wrapping 3-4 around an object and floating upwards to move an object).

They are capable of moving in all 6 directions without barriers or wind.

Glebsigi live on a planet with an atmosphere identical to Earth's atmosphere.

How could Glebsigi evolve from jellyfish/squid/octopi? How would their intelligence evolve?

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  • $\begingroup$ This might be easier if the creature doesn't actually support all it's weight buoyantly, but instead bounces along like a deflating helium balloon. Kind of pushing off for long, slow hops but still heavier than air. Gives you a little more margin. Also fits well with a life form who used to drag itself along just above the water. It could settle down in bad weather or even float on the water to rest, feed. $\endgroup$ – DWKraus Jul 26 '20 at 18:52
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Very slowly and probably not at all

Any evolution of the kind you suggest would have to happen over a long period of time. In reality, it's really unlikely that this could ever happen.

But since this isn't Biology SE, let's come up with a plausible way it theoretically could happen. You could have an aquatic create evolve an air bladder to control its buoyancy. Then imagine an evolutionary pressure to be as light as possible. Either food is just above the surface of the water or predators are on the prowl. Now imagine that this creature has a symbiotic relationship with a form of algae that produces hydrogen gas (which really exist). Over time, evolutionary pressures select for the creatures that rise the highest, eventually driving the winning creatures clear out of the water. As they gradually rose higher and higher, they'd have to evolve to breath dry air. And they would also need some way of controlling their movements in air, unless they use their tentacles to pull themselves along. They'd also have to have a really big air sack. Even with the lifting power of hydrogen, you'd need something like 100 cubic feet of the stuff to lift a 7-pound creature.

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    $\begingroup$ Watch out for strong winds! Or gentle breezes... $\endgroup$ – Joe Bloggs Jul 26 '20 at 6:53
  • $\begingroup$ @JoeBloggs yeah... they'd have the biggest weakness since the movie Signs $\endgroup$ – Andrew Brēza Jul 26 '20 at 19:30
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    $\begingroup$ If there was an evolutionary pressure to be as light as possible, that would affect not only their air bladder but also the density and weight of all of their tissue. So, if they did weigh 7 pounds, their tissue might have such low density that they might easily encompass a 100 cubic feet air bladder. $\endgroup$ – cowlinator Jul 28 '20 at 4:12
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    $\begingroup$ Also, they would be explosive. $\endgroup$ – cowlinator Jul 28 '20 at 4:13
  • $\begingroup$ @cowlinator those are really good points. You'd end up with huge explosive gas bags drifting with the breeze. $\endgroup$ – Andrew Brēza Jul 28 '20 at 13:31

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