The need to collect information on agricultural production has been with us since the dawn of civilisation. Agriculture was the main economic activity, supplying both food for growing populations and the basis for taxation. The Sumerians of Mesopotamia before 3000 BC developed writing systems in order to record crop yields and livestock numbers. The Ancient Egyptians recorded the extent and productivity of arable land on the banks of the Nile. Later conquerors surveyed their new possessions, as in the Norman conquest of England which resulted in the Domesday Book of 1086, recording the agricultural potential of each district in great detail.