Homo erectus

Homo erectus (/ˌhoʊmoʊ əˈrɛktəs/ lit. 'upright man') is an extinct species of archaic human from the Pleistocene, spanning nearly 2 million years. It is the first human species to evolve a humanlike body plan and gait, to leave Africa and colonize Asia and Europe, and to wield fire. H. erectus is the ancestor of later human species, including H. heidelbergensis — the last common ancestor of modern humans, Neanderthals, and Denisovans. As such a widely distributed species both geographically and temporally, H. erectus anatomy varies considerably. Subspecies are sometimes recognized: H. e. erectus, H. e. pekinensis, H. e. soloensis, H. e. ergaster, H. e. georgicus, and H. e. tautavelensis.

The species was first described by Eugène Dubois in 1893 as "Pithecanthropus erectus" using a skullcap, molar, and femur from Java, Indonesia. Further discoveries around East Asia were used to contend that humanity evolved out of Asia. Based on historical race concepts, it was argued that local H. erectus populations evolved directly into local modern human populations (polycentrism) rather than all humanity sharing a single anatomically modern ancestor (monogenism). As the fossil record improved over the mid-to-late 20th century, "Out of Africa" theory and monogenism became the consensus.

The typical skull has a pronounced brow ridge, a protruding jaw, and large teeth. The bones are much thicker than in modern humans. East Asian populations normally have an even more robust skeleton and larger brain volume — averaging 1,000 cc (61 cu in). Western H. erectus brain volume could be as low as 546 cc (33.3 cu in) in H. e. georgicus. H. erectus probably had a faster apelike growth trajectory, lacking the extended childhood required for language acquisition. Reconstructed adult body dimensions range from 141–167 cm (4 ft 8 in – 5 ft 6 in) in height and about 50 kg (110 lb) in weight.

H. erectus invented the Acheulean tool industry, a major innovation of large, heavy-duty stone tools. These may have been used in butchery, vegetable processing, and woodworking of spears and digging sticks. H. erectus was a major predator of large herbivores on the expanding savannas during the Quaternary glaciation. The species is usually characterized as the first hunter-gatherer and the first to practice sexual division of labor. Fire usage and cave habitation were probably not important aspects of daily life. Similarly, H. erectus may not have often ventured into colder regions or cooked meat. The last occurrence of H. erectus is 108,000 to 117,000 years ago (H. e. soloensis) in Southeast Asia, until the last savannas in the region gave way to jungle.

While Charles Darwin had hypothesized in his 1871 Descent of Man that humans most likely evolved in Africa, many late-19th century evolutionary naturalists postulated that Asia was the birthplace of humankind. Asia is midway between all continents via land routes or short sea crossings, providing optimal dispersal routes throughout the world. Among the major proponents of "Out of Asia" theory was Ernst Haeckel, who argued that the first human species (which he speculatively named Homo primigenius) evolved on a now-disproven hypothetical continent "Lemuria" from a species he termed Pithecanthropus alalus (speechless ape-man). "Lemuria" had supposedly sunk below the Indian Ocean, accounting for the lack of fossil evidence.

Dutch scientist Eugène Dubois joined the Royal Netherlands East Indies Army to search for the "missing link" of human evolution in Java. At the Trinil site, his team found a skullcap and molar in 1891, and a femur in 1892 (Java Man), which he named "Pithecanthropus erectus" in 1893. He attempted to convince the European scientific community that he had found an upright-walking ape-man dating to the late Pliocene or Early Pleistocene; they dismissed his findings as some kind of non-human ape.

Dubois argued that "P. erectus" was a gibbon-like ape which was the precursor to a more familiar human body plan, but in the 1930s, German-American anatomist Franz Weidenreich noticed a striking similarity with ancient human remains recently being unearthed in China (Peking Man, "Sinanthropus pekinensis"). This characterization became better supported as German-Dutch palaeontologist Gustav Heinrich Ralph von Koenigswald discovered more Indonesian ancient human remains over the decade at Mojokerto, Sangiran, and Ngandong. Weidenreich believed that they were the direct ancestors of the local modern human Homo sapiens subspecies, in accord with historical race concepts (polycentricism) — that is, Peking Man was the direct ancestor of specifically Chinese people, and Java Man of Aboriginal Australians. As the significance of racial distinction diminished with the development of modern evolutionary synthesis, many fossil human species and genera around Asia, Africa, and Europe (including "Pithecanthropus" and "Sinanthropus") were reclassified as subspecies of Homo erectus.

During the late 20th century, some of the oldest H. erectus fossils were discovered across Africa, the first being Kenyan archeologist Louis Leakey's Olduvai Hominin 9 in 1960. As the human fossil record expanded, the "Out of Africa" theory and monogenism became the consensus: that all modern humans share a fully anatomically modern common ancestor. H. erectus is now generally considered to be an African species which later dispersed across Eurasia, with later African populations giving rise to the modern human lineage.