Elves are mythological creatures, works of fantasy. But their is a hard core reality to them that is based in scientific fact. After examining what an elf IS, it is easy to see that there is a factual component to the myths. Like Schliemann finding Troy by reading Homer, we can find the real elves by examining the myths with a careful eye.
Elves are a mythological and anthropological artifact descended from Norse myths and folktales. They were originally very crude and ambiguously drawn fertility spirits and nature spirits. They evolved through their dispersion through Danish, Finnish and Germanic cultures into predominantly disease spirits, although these elves were most often the cause of minor irritations, like rashes and such. The primary trait of the original elves, as shown in the etymology of the word, was mainly a paleness of complexion. They were human, by and large, immortal, lithe and eternally youthful, but always pale. And most important, because it really isn't something intuitively true of mythological fertility or nature spirits in general, they love music and especially dance.
In time, elves became diminutive even as their role changed from the powerful and authoritative creatures of myth, to the petty and insignificant creatures of folklore. As they seemingly lost power and fame, they grew tiny and cute. After a time they became simple mischievous pranksters who could be bought off with some butter or warded with scary looking symbols. But they still retain their love of dance and music, even, in Scandinavian legends, being capable of dancing a man to death.
In modern times, beginning perhaps with Lord Dunsany and George MacDonald, and culminating in the J.R.R. Tolkien, elves were revisited and re-invigorated to their first status. The elves of Dunsany and MacDonald are quite different from the firefly faeries that populated children's books. And Tolkien's elves are sober and somber beings, wise and terrible. Tolkien is responsible, as no other man can claim, for bringing the elves back to their natural and original status as mythological powers. Their musical talents are highlighted in Tolkien's works, especially in their love for poetry.
So, what about the real elves? Well, strangely enough, human beings missing the gene for elastin, a deficiency called Williams Syndrome, which has symptoms that are very interesting indeed. Children with Williams syndrome display physical traits that are similar to what the myths portray as elven. They have pointy chins, upturned noses, long upper lips, wide mouths, full lips, small teeth. They have predominantly small frames and have trouble with low birth weight and low weight gain. Those with Williams Syndrome who have green or blue eyes often have an unusual starburst pattern to their iris. Their typical hypocalcemia can cause hyperreflexia, or involuntary movement, as well as periods of crankiness caused by muscle pain. Those with Williams Syndrome also have a sensitivity to sound at certain frequencies, often displayed as an overly-emotional response. In addition, children with Williams Syndrome display very particular mood and emotional traits. They are generally very friendly, outgoing, and sweet.
Now, it is a little stretch of the imagination to see in these symptoms, if colored by culture and superstition, plus a little old fashioned folk-exaggeration, the origins of a race of elves, perhaps changelings exchanged for human children. That they respond differently to music, that their appearance is so startling, seems very much more than coincidence. Is it likely that such a rare genetic condition was prevalent enough in this region to be misidentified as a supernatural race distinct from homo superstitiens? That might make a good thesis for a promising student in genetics.