While reading chapter 3 "Accumulating Small Change" of "The Blind Watchmaker" I came accross how different species around the world can evolve into similar traits. For example, the African and South American wekaly electric fish, use electric waves in a similar way but have their differences in shape (i.e., single fin on the back and single fin on the belly, respectively). If this type of similarities can be found with other species (bats, fish, dolphins, etc.) how come there isn't a human equivalent? How come the oldest human fossils are all found in Africa and theories point to modern humans migrating from Africa to the rest of the world. Shouldn't there be similar/equivalent fossils for the modern human in other parts of the world? I'm just curious to find out if there are clues, or theories that will explain why modern humans evolved from Africa only. Were there geographical factors or any other factors that drove natural selection into preventing evolution elsewhere?