George said that the people who built this place and the others, including Newgrange, probably practiced “excarnation,” in which the deceased would be left outside in the elements until only the skeleton remained, and some pieces of bone would then be deposited in the burial chamber with all the others.
This is a view from the main chamber outward along the passage.  The various constrictions in the passage (only about ten feet long) produce a square of light against the petroglyphs on the sunrises of the equinoxes.  This passage is also perfectly aligned with the Neolithic site at Tara; another site on a distant mountain to the north has a passage and chamber perfectly aligned with this site at Loughcrew.  It strikes me that if light can only get into these passage chambers from one direction, it could also only get out in one direction, so these structures could have been a Neolithic secure communications network as well as just bone yards or sun worship sites.  That might explain the hilltop locations of most of these places, too, since the whole island was densely wooded 5,000 years ago, making long sightlines in multiple directions rare.