... [E]lves are spirits and sprites, playing in eternal youth, living in the moment, powerful in magic and unconcerned about the future.... They are not HUMAN+... One elf lost in the world of the men, where actions have consequences and existence is weighty, does what the elf does - fights well with light weapons, and uses magic and stealth in the natural realm.
I think he has a perfectly valid take on the subject. I'd like to take that thread and run in a different direction.
Races in the Early Modern Period are "humans in funny hats." Just as Neanderthal man and Homo Sapien man evolved in proximity and shared Europe (whether you consider them as subspecies or distinct species), so have all the races in the EMP. Well, without one species going extinct in the process.
This racial condition presupposes a certain level of tolerance on the part of man that might seem out of place. In a world where an instant enmity might spring forth from minor differences, like say between neighboring German principalities, it is hard to imagine humans tolerating Elves, Dwarves, Gnomes, and the whole lot without someone going extinct.
So we just have to live with this seeming contradiction. There can still be plenty of room for racism and bigotry, similar to today, just with a lot less genocide of native populations.
All races have a common genesis but not a common ancestry. So each race evolved much like humans, developed societies, changed, and have arrived in their present fashion through the march of their own history. Of course, that history includes conflict and tolerance, stability and upheaval, with all of the ups and downs you might expect.
Now don't expect me to go and re-write history and include all these fun races in them. For the reality of running a D&D game, not a whole lot changes. This is just my conception of the fantasy races and why I use the AD&D convention of race + class and also why I removed racial limitations on class selection. Oh, and all races will have a similar lifespan. So sorry, there are no Elves around that got to hobnob with Romulus Augustulus and see the fall of the Roman Empire.