Danish Neolithic stone pulling

 This video is great fun, even if you don't understand Danish!  It's a good reconstruction of the methods by which goodness knows how many Neolithic burial chambers / long barrows / cromlechs were built all over Europe.  So these techniques were clearly available to the builders of Stonehenge, as were the techniques of tipping up extremely large monoliths (like those on Brittany) and placing them vertically in the ground.

So those techniques are not in question.  The really interesting question is this:  what are the conditions required for this activity to take place?  You need four things (at least):
1.  Motivation
2.  Technical ability and manpower
3.  A ready source of stones of the right sort
4.  Favourable physical conditions

That's what we really need to concentrate upon.  I have noticed that the successful stone hauling experiments have been done on flat or undulating terrain in dry conditions.  Obviously if your sledge or rollers are sinking into a bog forward movement of the stone will become impossible; and there also comes a point, on a slope of a certain gradient, where haulage upslope will become impossible even with vast numbers of men who have an unhindered route and a clear pulling trail. 

To me that suggests that Salisbury Plain (dry undulating chalkland) was good stone-pulling territory, whereas West Wales (with thin acid soils, frequent bogs, deep wooded river valleys with rushing streams, and more or less continuous Neolithic jungle covering the land surface) was not.

Around 4,500 years ago, when the "stone phase" of Stonehenge was under construction, what was the climate like?  According to Michael Allen, in the Early and Middle Neolithic there was still a lot of primeval forest left on Salisbury Plain, with thick deciduous woodland in the valleys and coombes, and with quite large areas of secondary woodland on the plain itself.  The area of grazed grassland was expanding all the time.  By the time of the "stone phase" (Late Neolithic) the clearance of primary forest is almost complete, and there is an almost continuous expanse of open grassland on the plain.  This cannot be coincidence.  Suddenly we have a large settled community based on farming, and a well developed social organization as well, allowing large-scale engineering projects to be initiated, if not actually completed.

And the haulage of stones was suddenly possible over an open landscape.  The crucial question is this:  how far afield were the stone collectors able to roam, given the technical and manpower resources that they had available?  Some thought needed on this.....