The Preseli stones from Stonehenge are approximately double the weight as the experimental block, but it is possible that one huge stone could have been brought by a group of just 20 people. The community living in the area during the Neolithic would have numbered several thousand so the absence of just a few dozen people was unlikely to cause any hardship. Doctoral student Barney Harris, who conducted the trial in Gordon Square, London, a stone's throw from UCL's Institute of Archaeology, said he was surprised that so few people had been required to move the block. "We were expecting...