One of the world's greatest ancient civilisations may have been built on llama droppings, a new study has found.Machu Picchu, the famous Inca city set in the Peruvian Andes, celebrates the centenary of its "'discovery" by the outside world this July. Dignitaries will descend on site for a glitzy event in July marking 100 years since US explorer Hiram Bingham came upon the site, but the origins of Machu Picchu were far less glamorous. According to a study published in archaeological review Antiquity, llama droppings provided the basis for the growth of Inca society. It was the switch from hunter-gathering...