A recent discovery of a Y-shaped wooden sledge at a megalithic site in Japan has lead a team of students from the Institute of Archaeology at London University's University College (UCL), to re-think how the Stonehenge stones were transported to the site.
     Previous ideas had centred on the impractical use of tree trunks as rollers. Experiments using these failed badly as, unless the trunks were exactly the same diameter as each other and perfectly round, the immense weight of the stones rolling over them would either crush them or push them into the ground.
     This new technique uses static 'rollers' with a smooth, low friction wooden sled being pulled over them. The experiment involved a slab of stone weighing a mere 1 ton and a team of 10 managed to pull it easily, at a steady speed of 1.6 km/hour. This lead to the belief that the 2 ton bluestones from the Preseli Hills in West Wales could have been transported in this way.
     It was not possible to confirm if the same technique could have been used for the much larger (32 ton) sarsen stones, albeit the journey would have been much shorter. Even the organisers were surprised with the ease with which the experiment worked.
     Event organiser, Barney Harris, from the Institute of Archaeology, is quoted as saying "All we can really tell from experiments like this is the minimum number of people involved. My preliminary calculations led me to believe it would take slightly more people. In the event, what I thought would take 15 people, at a minimum, actually needed only 10 people".
     More experimentation, over a variety of surfaces (this experiment was conducted over the smooth manicured grass of Gordon Square, adjacent to UCL) before a more accurate, revised estimate of the construction period for Stonehenge can be made

Edited from Live Science (17 June 2016)