Speculations About the Effects of Fire and Lava Flows on Human Evolution

Recent research argues that an association with fire, stretching back millions of years, played a central role in human evolution resulting in many modern human adaptations. Others argue that hominin evolution was driven by the roughness of topographic features that resulted from tectonic activity in the African Rift valley. I combine these hypotheses to propose that, for millions of years, active lava flows in the African Rift provided consistent but isolated sources of fire, providing very specific adaptive pressures and opportunities to small isolated groups of hominins. This allowed these groups of early hominins to develop many fire specific adaptations such as bipedalism, smaller teeth and mouths, shorter intestines, larger brains, and perhaps a host of social adaptations. By about 1.8 million years ago, Homo erectus emerged as a fire adapted species and mastered the technology necessary to make fire itself. This technology allowed them to move into the rest of the world, taking a new kind of fire with them that would change ecosystems everywhere they went. This hypothesis is supported by recent geologic work that describes a large lava flow occurring in the region of the Olduvai Gorge during the 200 000 year time period we believe Homo erectus emerged in the area.