Just a little correction, if I may offer it. The article asks:

> How did the bluestones, which weigh between four and eight tons apiece, arrive at the site, nearly 5,000 years ago, from 170 miles away in North Wales?

It's my understanding that the majority of the bluestones have been confirmed to come from the Pembrokeshire area in South West Wales, not North Wales.

Some searching returned these results:

http://www.bbc.co.uk/news/uk-wales-south-west-wales-16245746

http://www2.le.ac.uk/offices/press/pdf-files/uploaded-to-ebu...

Hope that's of some interest to folks...