A 5,000-year-old piece of chewing gum - one of the oldest ever to be discovered - has been found by a British archaeology student. The discovery of the Neolithic gum, made from birch bark tar, was made by Sarah Pickin, 23, during a dig in Finland. The gum had tooth prints in it. Trevor Brown, her tutor at the University of Derby, said: "Birch bark tar contains phenols, which are antiseptic compoun