Why is intelligence an advantage? It costs us a lot in energy to maintain our large brains.
The reason intelligence is an advantage is it allows you to adapt faster than evolution. Sort of.
To be precise, technology allows you to adapt faster than evolution, allowing an entity to adapt to multiple environments within one lifespan. Many creatures have technology - crows do, for example - but humans have it off to a fine art. When it gets cold, we put on clothes. When it gets hot, we turn on the air conditioning. We use technology to have fresh fruit in winter (when our ancestors got "winter sickness").
Technology even lets us start to adapt to the most hostile environment to life we yet know: Space.
So, technology is great. But what if you live in an environment that doesn't allow for technology. Say, the atmosphere of a gas giant - which has great conditions for life, but not great conditions for building things.
One group of earth creatures may have the answer: Cephalopods.
Octopi are proving to be remarkably intelligent creatures. They also have manipulative appendages, which are required to use tools. Some octopi build themselves little shelters out of coconut shells they carry around - not unlike a backpack tent. In captivity, octopi have been known to disassemble their tank. Or leave, throw the one bad shrimp from their lunch at the human who fed them, then crawl back in.
But, octopi are at a disadvantage when it comes to using technology to substitute for evolution. True, the coconut shell carriers are using technology so they don't have to evolve a shell. But they haven't built actual houses yet. Why? When you live underwater, you can't come up with some very key developments, like fire. (I'm leaving out the fact that most species of octopus die after breeding, so they have no culture for now).
The same thing might be true in other alien environments.
But octopi have come up with a different way to adapt faster than evolution allows: Editing their own RNA. Instead of following the instructions in their DNA to the letter, they alter them. And in squids and octopi, RNA editing affects the development of the nervous system. Which makes them smarter in the first place - but that's a side effect of increasing the variety of proteins they produce, allowing individuals to handle rapid changes in temperature. Without needing technology.
The downside is that their mutation rate is slower than those of other animals. They've sacrificed something of the ability to evolve - which is probably why they're still in the ocean. Which is also why most animals don't do that.
Humans do do some RNA editing, mind, mostly in primate-specific sequences. It's A-to-I editing in our case. And, RNA editing appears to play a role in psychiatric disorders - so do we also owe some of our intelligence to RNA editing? Maybe - unfortunately, everything I can find on human RNA editing is in thickly-written abstracts I don't have the time to decode right now.
But, how about some takeaways from this:
1. RNA editing may allow rapid adaptation at the price of slower evolution. It may be linked to intelligence.
2. Sentient species that live in environments where technology is difficult may be more likely to have a physiology that relies on it. Easy development of technology, though, allows for the same advantages without the slow mutation disadvantage.
3. What about cases where the mutation rate is extremely slow - could something like RNA editing actually be a primary evolutionary process on a world that isn't very well radiated. Extreme levels of RNA editing could allow for animals that can literally change form through their life (we aren't talking werewolf type shapeshifting here) but in-generation adaptations to, for example, extreme seasons.
4. Could we engineer our own descendants to use RNA editing to adapt - rather like the protagonist of the last third of Neal Stephenson's Seveneves.
5. Is this part of how Time Lords regenerate? (Because I can't resist).