The 7th millennium BC spanned the years 7000 BC to 6001 BC (c. 9 ka to c. 8 ka). It is impossible to precisely date events around this millennium, and all dates mentioned here are estimates mostly based on geological and anthropological analysis. Towards the end of this millennium, the islands of Great Britain, and Ireland were severed from continental Europe by rising seawater. Communities Population Neolithic culture and technology were established in the Near East by 7000 BC and there is increasing evidence through the millennium of its spread or introduction to Europe and the Far East. In most of the world, however, including north and western Europe, people still lived in scattered Palaeolithic hunter-gatherer communities. The Mehrgarh chalcolithic civilization began around 7000 BC. The world population is believed to have been stable and slowly increasing. It has been estimated that there were perhaps ten million people worldwide at the end of this millennium, growing to forty million by 5000 BC and 100 million by 1600 BC, an average growth rate of 0.027% p.a. from the beginning of the Neolithic to the Middle Bronze Age. Europe Neolithic culture and technology reached modern Turkey and Greece c. 7000 BC; and Crete about the same time. The innovations, including the introduction of farming, spread from the Middle East through Turkey and Egypt. There is evidence of domesticated sheep or goats, pigs, and cattle, together with grains of cultivated bread wheat. The domestication of pigs in Eastern Europe is believed to have begun c. 6800 BC. The pigs may have descended from European wild boar or were probably introduced by farmers migrating from the Middle East. There is evidence, c. 6200 BC, of farmers from the Middle East reaching the Danube and moving into Romania and Serbia. Farming gradually spread westward and northward over the next four millennia, finally reaching Great Britain and Scandinavia c. 3000 BC to complete the transition of Europe from the Mesolithic to the Neolithic. Near East The Ubaid period (c. 6500–3800 BC) began in Mesopotamia, its name derived from Tell al-'Ubaid where the first significant excavation took place. By the end of this millennium, Tell es-Sultan (Jericho) had become a large agricultural settlement with some eight to ten acres within its walls. Kathleen Kenyon reckoned that it was home to about three thousand people. Construction was done using stone implements to mould clay into bricks. The main