ABSTRACT
It is well established that all of the events in early human evolution took place in East Africa where tectonic activity had resulted in formation of Great Rift Valley and Olduvai Gorge. The two main rift valleys consisted of mainly inland salt water lakes in the east and large fresh water lakes to the west. Evidence suggests that many of these lake basins were transient and highly sensitive to local climatic changes. The finding of hominin fossils and tools here and elsewhere has allowed archaeologists to identify four main stages in human evolution, which are discussed.
The importance of salt balance in cellular processes in the body and hominin kidney adaptations to a waterside aquatic habitat is explained. The structure of the human kidney with multiple pyramids is described and how this is similar to aquatic mammals, but is different from the kidneys of other terrestrial mammals, with the exception of the camel. (153 words)
