Homo erectus

Homo erectus
Homme de Tautavel 01-08.jpg
Reconstructed skeleton of
Tautavel Man[2]
Scientific classification edit
Kingdom:Animalia
Phylum:Chordata
Class:Mammalia
Order:Primates
Suborder:Haplorhini
Infraorder:Simiiformes
Family:Hominidae
Subfamily:Homininae
Tribe:Hominini
Genus:Homo
Species:
H. erectus
Binomial name
Homo erectus
(Dubois, 1893)
Synonyms

Homo erectus (meaning 'upright man') were a species of archaic humans from the Pleistocene, earliest occurrence about 2 mya. They are proposed to be the direct ancestors to several human species, such as H. heidelbergensis, H. antecessor, Neanderthals, Denisovans, and modern humans.[3][4] As a chronospecies, the time of its disappearance is thus a matter of contention or even convention. There are also several proposed subspecies with varying levels of recognition.

H. erectus appear to have been much more similar to modern humans than to their ancestors, the australopithecines, with a more humanlike gait, body proportions, height, and brain capacity. H. erectus are associated with the Acheulean stone tool industry, and is thought to be the earliest human ancestor capable of starting fires, speech, hunting and gathering in coordinated groups, caring for injured or sick group members, and possibly art-making.

Taxonomy

Naming

The first remains, Java Man, were described by Dutch anatomist Eugène Dubois in 1893, who set out to look for the "missing link" between apes and humans in Southeast Asia, because he believed gibbons to be the closest living relatives to humans in accordance with the "Out of Asia" hypothesis. H. erectus was the first fossil hominin found as a result of a directed expedition.

Excavated from the bank of the Solo River at Trinil, East Java, he first allocated the material to a genus of fossil chimpanzees as Anthropopithecus erectus, then the following year assigned it to a new genus as Pithecanthropus erectus (the genus name had been coined by Ernst Haeckel in 1868 for the hypothetical link between humans and fossil Apes). The species name erectus was given because the femur suggested that Java Man had been bipedal and walked upright. However, few scientists recognized it as a "missing link", and, consequently, Dubois' discovery had been largely disregarded.[5]

Forensic reconstruction of an adult female Homo erectus.[6]

In 1921, two teeth from Zhoukoudian, China discovered by Johan Gunnar Andersson had prompted widely publicized interest.[7] When describing the teeth, Davidson Black named it a new species Sinanthropus pekinensis from Ancient Greek Σίνα sino- "China" and Latin pekinensis "of Peking". Subsequent excavations uncovered about 200 human fossils from more than 40 individuals including five nearly complete skullcaps.[8] Franz Weidenreich provided much of the detailed description of this material in several monographs published in the journal Palaeontologica Sinica (Series D). Nearly all of the original specimens were lost during World War II during an attempt to smuggle them out of China for safekeeping. However, casts were made by Weidenreich, which exist at the American Museum of Natural History in New York City and at the Institute of Vertebrate Paleontology and Paleoanthropology in Beijing.

Similarities between Java Man and Peking Man led Ernst Mayr to rename both as Homo erectus in 1950. Throughout much of the 20th century, anthropologists debated the role of H. erectus in human evolution. Early in the century, due in part to the discoveries at Java and Zhoukoudian, the belief that modern humans first evolved in Asia was widely accepted. A few naturalists—Charles Darwin the most prominent among them—theorized that humans' earliest ancestors were African. Darwin pointed out that chimpanzees and gorillas, humans' closest relatives, evolved and exist only in Africa.[9]

Evolution

Forensic reconstruction of an adult male Homo erectus.[10]
Map of the distribution of Middle Pleistocene (Acheulean) cleaver finds

It has been proposed that H. erectus evolved from H. habilis about 2 mya, though this has been called into question because they coexisted for at least a half a million years. Alternatively, a group of H. habilis may have been reproductively isolated, and only this group developed into H. erectus (cladogenesis).[11]

Because the earliest remains of H. erectus are found in both Africa and East Asia (in China as early as 2.1 mya[12][13][14][15]), it is debated where H. erectus evolved. A 2011 study suggested that it was H. habilis who reached West Asia, that early H. erectus developed there, and that early H. erectus would then have dispersed from West Asia to East Asia (Peking Man), Southeast Asia (Java Man), back to Africa (Homo ergaster), and to Europe (Tautavel Man), eventually evolving into modern humans in Africa.[16][17] Others have suggested that H. erectus/H. ergaster developed in Africa, where it eventually evolved into modern humans.[18][19]

Subspecies

"Wushan Man" was proposed as Homo erectus wushanensis, but is now thought to be based upon fossilized fragments of an extinct non-hominin ape.[23]

Since its discovery in 1893 (Java man), there has been a trend in palaeoanthropology of reducing the number of proposed species of Homo, to the point where H. erectus includes all early (Lower Paleolithic) forms of Homo sufficiently derived from H. habilis and distinct from early H. heidelbergensis (in Africa also known as H. rhodesiensis).[24] It is sometimes considered as a wide-ranging, polymorphous species.[25]

Reconstruction of Homo georgicus based on D2700, by Élisabeth Daynès, Museo de la Evolución Humana, Spain.

Due to such a wide range of variation, it has been suggested that the ancient H. rudolfensis and H. habilis should be considered early varieties of H. erectus.[26][27] The primitive H. e. georgicus from Dmanisi, Georgia has the smallest brain capacity of any known Pleistocene hominin (about 600 cc), and its inclusion in the species would greatly expand the range of variation of H. erectus to perhaps include species as H. rudolfensis, H. gautengensis, H. ergaster, and perhaps H. habilis.[28] However, a 2015 study suggested that H. georgicus represents an earlier, more primitive species of Homo derived from an older dispersal of hominins from Africa, with H. ergaster/erectus possibly deriving from a later dispersal.[29] H. georgicus is sometimes not even regarded as H. erectus.[30][31]

It is debated whether the African H. e. ergaster is a separate species (and that H. erectus evolved in Asia, then migrated to Africa),[32] or is the African form (sensu lato) of H. erectus (sensu stricto). In the latter, H. ergaster has also been suggested to represent the immediate ancestor of H. erectus.[33] It has also been suggested that H. ergaster instead of H. erectus, or some hybrid between the two, was the immediate ancestor of other archaic humans and modern humans.

In a wider sense, H. erectus had mostly been replaced by H. heidelbergensis by about 300 kya years ago, with possible late survival of H. erectus soloensis in Java an estimated 546–143 kya.[1]

Dmanisi skull 3 (fossils skull D2700 and jaw D2735, two of several found in Dmanisi in the Georgian Transcaucasus)

Descendents and synonyms

Homo erectus is the most long-lived species of Homo, having survived for over a million years. By contrast, Homo sapiens emerged about a quarter million years ago.

Regarding many archaic humans, there is no definite consensus as to whether they should be classified as subspecies of H. erectus or H. sapiens or as separate species.

If considering Homo erectus in its strict sense (that is, as referring to only the Asian variety) no consensus has been reached as to whether it is ancestral to H. sapiens or any later human species.[citation needed] Similarly, H. antecessor and sisters, including modern humans, appear to have emerged specifically as sister of, for example, the Asian variety of H. erectus.[36] Moreover, some late H. erectus varieties may have introgressed into the Denisovans, which then later introgressed into H. sapiens.[37] However, it is conventional to label European archaic humans as H. heidelbergensis, the immediate predecessor of Neanderthals.

Meganthropus refers to a group of fossils found in Java, dated to between 1.4 and 0.9 Mya, which are tentatively grouped with H. erectus, at least in the wider sense of the term in which "all earlier Homo populations that are sufficiently derived from African early Homo belong to H. erectus",[24] although older literature has placed the fossils outside of Homo altogether.[38]