Here's a tentative hypothesis:
- Complexity (intelligence) in life is high-cost, and only happens as a result of selective pressures favoring higher processing power and flexible solutions. Homeostasis is more ideal, where a species survives just fine in its present form for billions of years, as we've seen with some here on earth. If a species isn't challenged, it won't grow.
- Challenging selective pressures favoring higher processing and flexible solutions require... mobility, dexterity, and a computational matrix (i.e. brain). A tree doesn't have that many problems to solve. But a dynamic species does, as it tracks food/resources, predators, etc. Problems. Problems.
- This gets us up to ravens and cuddlefish. These kinds of creatures have dexterity, mobility, and processing. So they're very clever about how they innovate to get food. HOWEVER... they are capped, imo.
- Dolphins are a step up from ravens and cuddlefish because of the social aspect. Why? Because the social aspect is another --even more computationally taxing problem (just ask an aspie!) -- that requires a lot of abstraction. So I see socialization as one of the most likely additional factors that works as a selective pressure for a species to solve complex problems.
Essentially, at some point the "abstraction" has to detach itself from the environment. Humans interface with ideas, as if ideas were objects in the world. We "problem solve" in a conceptual space, simulating scenarios that don't exist.
I can't think of another selective pressure that would catalyze that sort of abstraction, aside from socialization and language-development, which go hand in hand. Language development is what allowed us to abstract concepts, and we developed language to communicate with each other.
So I would add: language (which implies socialization) as a fourth criteria, giving us:
- mobility
- dexterity
- processing
- language
What do you guys think?
edit: of a higher nuances than "meow"
we need to be able to relay very specific information ("i put the spear under my tent, go get it, we need you to hunt with us").