The earliest evidence of humans using fire comes from many archaeological sites in East Africa, like Chesowanja near Lake Baringo, Koobi Fora, and Olorgesailie in Kenya. The evidence at Chesowanja is the discovery of red clay shards that scientists estimate are 1.42 million years old. Scientists reheated some of the shards at the site, and found that the clay must have been heated to 400 °C to harden.