Prehistoric humans, also known as cavemen, were the earliest known species of human beings. They lived during the Paleolithic period, which lasted from about 2.5 million to 10, 000 years ago. During this time, they used stone tools and hunted animals for food. Another prehistoric human species was Java Man, who lived in Indonesia during the Pleistocene period, which lasted from about 2.6 million to 11, 700 years ago. Java Man is believed to be the ancestor of modern humans.