Let's not get into real world science here. Other races can be smarter because of physical reasons that'd we'd understand, physical reasons that are beyond real-world humanity's current understanding, or simply "Because Magic." E.g., elves, dragons, etc. are inherently magical.
Agreed. In my head cannon high elves got the +1 intelligence because intelligence is the arcane magic ability score and magic is emphasized in elven culture and they had about 80 more years of schooling than did humans. If you become an adult at age 100 you've been thinking about magic longer than 99% of human wizards.
On Wolfheart - I mostly agreed with him but I found his efforts to avoid offending anyone rather painful. We should have the option of either system. But if you are going to bring in the (unpopular) Tasha's system you should do it correctly.
The species ability bonuses listed in the PHB scores should be the default and if people want to switch to the boring, lore-destroying Tasha's alternative they can do so. Because remember it's not ASI's that make the races interesting it's things like being blind in the dark and moving slower than other species!
