Changelings are part of Western Folklore, a child of a fairy type (Elf, Troll etc) which has been secretly swapped for a human baby and left in its place. George Waldron gave the following description of one he saw in the Isle of Man and it was subsequently reprinted in ‘The Science of Fairy Tales’ (1891) by Edwin Sidney Hartland.
The UFO community is pretty strange. You can find literally hundreds of books and websites devoted to cases which have left not even the most insignificant evidence while cases with solid physical evidence (which may or may not be of extraterrestrial origin, but that’s another matter) tend to be forgotten or ignored.
La Hogue Bie is a major Neolitic ritual site dating back to 3500BC and one of the best preserved cruciform passage graves in Europe. Its passage is twenty meters long and is covered by a 12.2 meter high earth mound. The mound istelf is 58 meters in diameter and covers an area of 2400 square meters.