This week's programmes in the history of the world look at the growing sophistication of modern humans around the globe between 5000 and 2000 BC. Mesopotamia had built the royal city of Ur, the Indus valley boasted the city of Harappa, and the great early civilisation of Egypt was beginning to spread along the Nile. In Britain life was much simpler, although trade links with Europe were well established. In today's programme, Neil Macgregor tells the story of a beautiful piece of jade, shaped into an axe head. It is about 6000 years old and was discovered near Canterbury in Kent but was made in the high Alps. Neil MacGregor tells the story of how this object may have been used and traded and how its source was cunningly traced to the heart of Europe