1) Africa is considered the cradle of humanity, as the oldest human skeletons have been found in East Africa, including a female skeleton nicknamed "Lucy" dated to 3.6-3 million years ago. 2) Several human species emerged in Africa over time, including Homo habilis, Homo erectus, and Homo sapiens, with Homo erectus living 1.5 million to 250,000 years ago. 3) Early humans like Homo erectus showed evidence of walking upright 3.5 million years ago based on footprints found in East Africa.