Ancestors mostly from africa or parts of asia. Closely related to monkeys, who suffer similar parasites, fungi, etc. Monkeys can be infected by 15-20 species of malaria. Humans can be infected by: both can suffer from malaria from eachother. Tiny organisms like in tropical rain forests, not cool and dry so they can live on their own until host comes along. People got smarter, made weapons better survival and food supply. Human cultural evolution threw off biological evolution. Language came next, making them more human. New parasites came in (or worms) that can infect humans by eating meat. Trypanosome (sleeping sickness) in africa in antelope transferred to humans by testes fly. Balance because people herd fly back to people. Herds became prey of other adapted animals, not just people. Prehumans and protohuman lagged behind the african population. 8000 b. c. human hunting groups expanded all around the globe. Human population went up = rate of infection went up.