My guess is they're druid, like Stone Henge.
Stonehenge pre-dates the druids and had nothing to do with them when it was built. The druidic connection was invented in the 19th century by people who wanted to resurrect their "ancestral" religion but had no real idea what they were doing.
That's right, these stone circles pre-date the Druids.
There is still no consensus on why they were built and what they were for.
At the start of the video it shows a glimpse of Silbury Hill which is - I believe - the largest man-made ancient hill in the world, it is only a stones throw from the Avebury stones, but again, no-one is sure why it was built and what it was for. It's proximity to Avebury obviously makes ppl think there was a link, but who knows.
I guess places of holy pilgrimage have always been part of human existence. The Hajj to Mecca is just one that's still alive.
I have always thought the kissing of the stone in the Ka'ba was a pre-historic custom. Perhaps the pilgrims to Avebury also kissed stones.
Man is always reaching out to God - and in the absence of God - stones will do! LOL