Well, what is called Tolkien elves these days sort of predate modern fiction though. Members of the elves in various cultures were largely just beautiful humans with mysterious ways. Some were not of course.
At any rate elven variance could be easily explained with their closeness to the weave and being more fluid in shape in form although that cribs a lot from Wendy pinis elfquest.
A (primarily) Chaotic Good race of wanderlust-stricken hedonists? Methinks more of their ancestors were knocking Boots of Elvenkind with "lowly humans" than they care to admit.