Using isotope analysis, which identifies chemical signals from the food and water that animals have consumed, the researchers were able to determine geographical areas where the pigs were raised. The study offers the most detailed picture yet of the degree of mobility across Britain at the time of Stonehenge. Dr Madgwick said: "Arguably the most startling finding is the efforts that participants invested in contributing pigs that they themselves had raised. Procuring them in the vicinity of the feasting sites would have been relatively easy. "Pigs are not nearly as well-suited to movement over distance as cattle and transporting them, either slaughtered or on the hoof, over hundreds or even tens of kilometres, would have required a monumental effort. "This suggests that prescribed contributions were required and that rules dictated that offered pigs must be raised by the feasting participants, accompanying them on their journey, rather than being acquired locally." - www.sciencedaily.com