Modern humans evolved in Africa beginning around 200,000 years ago, from where they spread first to the Middle East and thence to Asia and Australia. They were hunter-gatherers who developed a profound knowledge of the natural environment and evolved a sophisticated material culture in the course of their search for food and shelter. A large number of their temporary and semipermanent settlement sites have been discovered and excavated in different parts of mainland Southeast Asia reaching back some 40,000 years.