Cairns - certainly rough cairns - were built in pairs near the top of a hill where they would appear on the horizon from a stone circle or other ceremonial site below. This is well known and fairly mainstream. The moon at the northernmost setting place could have a pair of cairns to 'frame' the calendrically important place. The moon just gets there once every 18 years eg. These little cairns are very prominent on the horizon, from lower down, but there are sink holes and a fairly new valley where a small stone circle or row might have been.

There's also a very low standing stone about twenty yards away, on the low side of the cairns. (I'd forgotten about that). I only found it this summer. It 'points' at the lower cairn. Practically shepherds are lacking in imagination. They make sheep folds well but would need an active tradition of this-kind-of cairn building to be able to build a pair with such fluidity. The only time such a tradition existed, I would argue, was in the Neolithic/Early Bronze Age. (You could also try and persuade me Iron Age, perhaps contemporary with the Romans, but certainly no later than that). The shape is reminiscent of turned shield bosses, perhaps ?