John Hanning Speke arrange a better relationship for Mere with another man, without success it seems. Finally, given permission by Mutesa in June 1862 to leave, Speke then travelled down the Nile now reunited with Grant. Because of travel restrictions placed by the local chieftains, slave raiding parties, tribal wars and the difficulty of the terrain, Speke was not able to map the entire flow of the Nile from Lake Victoria north. Why he did not make more efforts to do so is not clear, but the enormous hardships of the journey must have played a large role. By January 1863 Speke and
Hamites races were too broad to have stemmed from a single common ancestor, but were instead consistent with separate racial origins. In his "Crania Aegyptiaca" (1844), Morton analyzed over a hundred intact crania gathered from the Nile Valley, and concluded that the ancient Egyptians were racially akin to Europeans. His conclusions would establish the foundation for the American School of anthropology, and would also influence proponents of polygenism. In the second half of the 19th century, the British explorer John Hanning Speke would further popularize the ancient Hamitic peregrinations in his publications on his search for the source of the Nile