The argument that in real life intelligence and social behaviour is strongly linked thus the it should in the game too is a pretty bad argument tbh and would if anything only make the game far far worse. The whole point with fantasy is to allow concepts that would be impossible/improbable in the real world and through that create a much more interesting setting.
I'd argue that occasional bands of various creatures are far more interesting than solitary monsters who happen to be allegedly sentient.
For that matter, do we even know if evolution works withing the DF setting? Any confirmation from Toady on the matter, or is that just as much speculation and making things up as saying "a wizard did it"?
There's equal speculation on both sides, but one side is based on real-world science (supported by the timescales implied by the real-world geology) and the other is random guesses based on how creation myths usually are.
And regarding the ogres, what evidence suggests they are mammals?
They have hair and are shaped like primates.
Most ogres in fantasy also share mammalian, and often specifically primate, characteristics such as hair and dextrous hands.
To apply real world rules like that to something that in my opinion should definitely not follow real world rules only serves to simplify the game and make the setting less interesting. Fantasy elements should follow logical rules, but their own rules, not those of the real world which once again the whole point of fantasy is to differ from.
I disagree with your argument, because it is based on faulty principles. I could use an analogous argument to argue against including
trees or
iron in DF. They're real-world stuff, we should replace them with fantasy BS that follows its "own rules, not those of the real world which once again the whole point of fantasy is to differ from."
I for one find the notion of various semi-megabeasts or megabeasts grouping up with other types off-putting, as it doesn't conform to how I want to see them implemented, but I realize that's mostly a matter of taste. Smaller groups of beasts on occasion sounds like a great idea for some of them, but if so it should be because it fits the setting and the game, not because of trying to project real world rulesets where they don't belong (ie the fantasy elements) ^^
Why should groupings of different kinds of beasts be different than:
1. Groupings of the same kind of beast?
2. Civilizations of mixed race?
3. Adventuring parties of mixed race?
4. Real-world groups which, despite their outward and cultural differences, managed to work together?
5. Real-world symbiosis and/or domestication?
