Oppenheimer writes that there was only one migration out of Africa that contributed to the peopling of the rest of the world. Oppenheimer believes that anatomically modern humans crossed the Red Sea from the Horn of Africa and followed the "southern coastal route" once in Asia. Thus Oppenheimer is opposed to the theory that there was another out of Africa migration using a northern route along the Nile and into the Levant as suggested by Lahr and Foley 1994. The book also supports the theory that modern humans were in South Asia during the Toba catastrophe.