The Oldowan is the archaeological term used to refer to the stone tool industry that was used by hominids during the earliest Palaeolithic period. For a long time it was thought that the Oldowan was the earliest stone tool industry in prehistory, from 2.6 million years ago up until 1.7 million years ago. It was followed by the more sophisticated Acheulean industry. Oldowan tools were therefore the earliest tools in human history, and mark the beginning of the archaeological record. The term "Oldowan" is taken from the site of Olduvai Gorge in Tanzania, where the first Oldowan tools were discovered by the archaeologist Louis Leakey in the 1930s. Now it is realised that stone tools were used much earlier (3.3 million years ago) and that was definitely before the genus "Homo" had evolved.