Lake sediments are valuable archives of past environmental change. We examine the pollen, diatom and geochemical composition of lake sediment cores to reconstruct past climate, vegetation and human impact. Current projects include the Late Pleistocene history of the Blue Nile catchment, Ethiopia. Cores taken in October 2003 from Lake Tana, the source of the Blue Nile, reveal that the lake was dry between 16,500 and 15,500 years ago. Ongoing research is focused on the question of whether the lake also ceased to outflow into the Blue Nile at 4200 years ago, causing the droughts that brought the downfall of the Egyptian Old Kingdom.