Sites in Turkey, including the famous Gobekli Tepe, show that before agriculture, hunter-gatherers started harvesting wild grasses. They were using the ancestors of wheat and barley to make beer - crushing them up in big tubs and leaving them to ferment. They found hundreds of these tubs and even simple musical instruments. What were they doing - having a festival of course. At this proto-Glastonbury hunter gatherer groups would come from miles around to drink, listen to someone rock out on the deer-horn flute and enjoy themselves.