 Schmidt's preheating hypothesis was also tested and again supported by S. Terry Childs in 1996.Pollen core samples in the region document the loss of forested habitats and the expansion of grasslands beginning around the 2nd millennium BC and continuing up to the 11th century AD.It is argued that part of the advancement of grasslands in Kagera Region was due to iron smelting as it required the production of charcoal on a large scale.