I put forward the theory(a long time ago in a forum far far away)that as the winters in times gone past were more severe...the hunting would be thin so food would've been previously stored during the appropriate season. Rather than have the men sit around doing nothing(can see the looks on the faces of the women with those hulking brutes laying about under their feet...it's reflected in the face of modern woman every time she tries to hoover around a man watching telly today......) they went and gathered the stones from afar... the stones were transported over snowy wastes by sled(easier than by dry land or sea) as a form of community service and tribal bonding and the stones would be needed to replace wood as a more permanent edifice...several birds killed with one stone(NPI)...the men had something to do,wooden "henges" got replacement building materials and tribal morale was sustained.
Perhaps there was some form of barter involved..hunters swapped food with quarriers???
Only an idea.
All fuel added to an ever-increasing fire Resonox! Somewhere amongst all the ideas the truth lies hidden but is probably a combination of sorts of many of those ideas. In the meantime ideas seem to change with the weather don't they with one one person (archo or otherwise) putting a theory forward only to have the next one knock it down!!