What do you picture when you think about Neanderthals? Probably something like this: Prominent brow, big nose, lots of hair, and tiny, close set eyes. People think of Neanderthals with stone tools, spearing mammoths, being ambushed by Cro-Magnons. But people hardly think of Neanderthals as having any kind of spiritual inclination. Newgrange was built during the Neolithic period, around 3200 BC, making it older than the pyramids and stonehenge. It is speculated by archeologists that it was built to serve a religious purpose, which for me, is probably the most interesting aspect of Newgrange.
Although pictures inside were not allowed, you can see from the outside on the entrance stone the swirl pattern that was present in much of the chamber. Not much is known about this pattern. It is speculated to mean anything from life to psychedelic mushrooms. What I think is interesting is that, although the meaning remains unknown, everybody acknowledges that it must have some meaning. We think about Neanderthals as being akin to apes: unintelligible. But here we have a complex structure built by them, one that might have been used for spiritual/religious purposes. In order to have religion, one must first have a mind. And so, to me, Newgrange is an amazing example of the fact that the Neanderthals might have had sentience, although we typically do not interpret them that way.
If you are inside of Newgrange on the Winter Solstice, you can see the whole chamber light up for a solid seventeen minutes. Nobody knows what this means. What they do know is that Newgrange was constructed geometrically so that this illumination of the chamber would happen every year during the Winter Solstice. This is consistent with the notion that Newgrange was built for religious purposes. Why else would they construct it so that it would only be fully lit for a mere seventeen minutes out of the year?
To have spiritual beliefs is to have a mind. You can look at bones, you can carbon date them, but you cannot measure the capacity to have consciousness (just yet). Newgrange was a wonderful compliment to the idea that the Sciences and Humanities must diverge to get the whole picture.