Researchers from the School of Geography and the Environment at the University of Oxford surveyed the now-dry basin of Lake Makgadikgadi in the Kalahari Desert, which at 25,000 square miles is about the same size of present-day Lake Victoria. Their research was prompted by the discovery of the first of what are believed to be the world’s largest stone tools on the bed of the lake. Although the first find was made in the 1990s, the discovery of four giant axes has not been scientifically reported