H. erectus originally migrated from Africa during the Early Pleistocene, possibly as a result of the operation of the Saharan pump, around 2.0 million years ago, and dispersed throughout much of the Old World. Fossilized remains 1.8 and 1.0 million years old have been found in Africa (Lake Turkana and Olduvai Gorge), Europe (Georgia, Spain), Indonesia, Vietnam, and China.
Dutch anatomist Eugene Dubois, who was fascinated especially by Darwin's theory of evolution as applied to man, set out to Asia to find a human ancestor in 1886. In 1891, his team discovered a human fossil on the island of Java, Indonesia. Dubois described the species as Pithecanthropus erectus, based on a calotte (skullcap) and a femur like that of H. sapiens found from the bank of the Solo River at Trinil, in East Java. This species is now regarded as Homo erectus. This find became known as Java Man.
Throughout much of the 20th century, anthropologists debated the role of Homo erectus in human evolution. Nevertheless, early in the century, due to discoveries on Java and at Zhoukoudian, it was believed that modern humans first evolved in Asia. Only a few naturalists, such as Charles Darwin, predicted that humans' earliest ancestors were African: he pointed out that chimpanzees and gorillas, obviously human relatives, live only in Africa.
From 1950s to 1970s, however, numerous fossil finds from East Africa yielded evidence that the oldest hominins originated there. It is now believed that H. erectus is a descendant of earlier genera such as Ardipithecus and Australopithecus, or early Homo Genuses, such as H. habilis or H. ergaster. H. habilis and H. erectus coexisted for several thousand years, and may represent separate lineages of a common ancestor.