Structural differences in their larynx, tongue, or lips seem likely.
I must say I'm already a big fan of Pelia.
Spock is visibly affected by bloodwine and gets a hangover, although he states in TOS: “The Conscience of the King” that “My father’s race was spared the dubious effects of alcohol.”
Personally I always took that not as "Vulcans aren't affected by alcohol", but "Vulcans historically have no culture of drinking."
As always, I feel compelled to point out that Turkana IV was never said to have been a member of the Federation - they “severed relations” with the Federation, but that doesn’t necessarily mean they were a member (in fact, I think it strongly suggests that they were not, as that’s a very clunky way to refer to secession).
That's a reasonable objection to raise but I'd counter with the point that it seems unlikely that a human colony could be established except under the auspices of the Federation, or at least United Earth.
Well, his big successes were early, right? Maybe the institute was too.
He was a frontline doctor during a conflict with an enemy that considers medics viable targets.