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.
Perhaps, but as I stated that's more am matter of taste than anything, the argument is still a bad one imo.
It's a bad argument to use either way, and for the exact same reasons.
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.
Seeing as currently most beings seem to be created at the start of world gen I'd say the random guesses based on creation myth would be more logical then evolution then 
"In a time before time..." precedes the explanation of every megabeast, semimegabeast, demon, and forgotten beast's first event in Legends Mode. Look it up; you can't miss it.
This
proves that there was time before Year 1, which
proves that evolution could have occurred.
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.
Neither are much solid evidence of having a common evolutionary background though. The real world is full of examples of convergent evolution (dolphins resembling sharks for example) with completely different evolutionary background of the resembling features.
...Except that hair is a defining mammalian characteristic (as is endothermism, implied by the ogre's HOMEOTHERM tag), as digits are a primate one. Convergent evolution is for things like shape. It applies to amphibian men (who, even apart from the name, are pretty clearly non-mammalian), but not to more "minor" characteristics like fur and digits, which are identifying and idiosynchraic of assorted clades.
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."
What faulty principles? I also think you misunderstand me, I'm not saying there should be no "real-world stuff", or that they should not follow real world rules. I'm just saying that trying to impose real-world rules on clear fantasy features will only limit and lessen them into something that is no longer fantasy. If you want all the fantasy beings in the game to be shoe-horned into fitting real world scientific principles then I'm fairly certain a whole lot of the current game would have to be scrapped completely. The ratio of real world to fantasy elements on the other hand is a whole seperate can of worms which is also mostly a matter of taste.
On the other hand, saying real-world natural laws don't apply to DF is essentially what you're doing. You're saying that my arguments based on real-world biology are invalid because of their inapplicability to a fantasy world; I'm saying that arguments [for iron being present in DF, say] based on real-world geology, metallurgy, chemistry, etc, are invalid for exactly the same reason. How is this not an apt analogy?
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?
In my mind a giant and minotaur for example are simply not the kind of beings that would group up. Trying to argue against opinions on flavour though is rather pointless imo ;P
You...kinda didn't answer my question.
At all.
What makes a group of, say, minotaurs and ogres different from any of the 5 analogous examples provided? They cover mostly fantasy bases--the only ones you accept as germane--as well as real-world ones--which can be concretely proven.
