Stonehenge and its Environs 134
Image by RiotGibbon

GordonP wrote:
Nothing difficult about loading a 6 ton stone onto a boat. Not even in Neolithic times.
Hmmm -- nothing difficult in theory, maybe, but in a real world of slippery river-banks, tides and fast-flowing streams? I was involved in the Millennium Stone project in 2000. The organizers thought it would be easy to shift the bluestone from the shore at Blackpool Mill onto the two trussed-together curraghs. Total shambles. A JCB and a heavy lift crane both had to be brought in to do the job. Then a bit later the stone was lost onto the bed of Milford haven and had to be recovered with the aid of divers and a salvage pontoon. The full exciting story here:
http://www.brianjohn.f2s.com/enigma2.html

You seem a tad keen to find reasons to rule out human transportation. As I mentioned, the Millenium project was a shambles but I was a witness to Gordon's project which convinced me it was a possibility. That, plus the fact I was aware the date range of suitable boats has been pushed back and a boat has been found loaded with stones are three recent reasons why I reckon human transportation is quite a viable speculation.

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Hmmm -- nothing difficult in theory, maybe, but in a real world of slippery river-banks, tides and fast-flowing streams?

Load the boat on the beach while the tide is out then just wait for the tide to come in.

I could easily load a 6-ton stone onto a craft similar in construction to the Ferriby boat in less than 3 hours.