Homo erectus

Homo erectus (Latin: "upright man") is an extinct species of the genus Homo. Dutch anatomist Eugene Dubois (1890s) first described it as Pithecanthropus erectus, based on a calotte (skullcap) and a modern-looking femur found from the bank of the Solo River at Trinil, in central Java. However, thanks to Canadian anatomist Davidson Black's (1921) initial description of a lower molar, which was dubbed Sinanthropus pekinensis, most of the early and spectacular discoveries of this taxon took place at Zhoukoudian in China. German anatomist Franz Weidenreich provided much of the detailed description of this material in several monographs published in the journal Palaeontologica Sinica (Series D). However, nearly all of the original specimens were lost during World War II. High quality Weidenreichian casts do exist and are considered to be reliable evidence; these are curated at the American Museum of Natural History (NYC) and at the Institute of Vertebrate Paleontology and Paleoanthropology (Beijing).

Throughout much of the 20th century, anthropologists debated the role of H. erectus in human evolution. Early in the century, due to discoveries on Java and at Zhoukoudian, it was believed that modern humans first evolved in Asia. This contradicted Charles Darwin's idea of African human origin. However, during the 1950s and 1970s, numerous fossil finds from East Africa (Kenya) yielded evidence that the oldest hominins originated there. It is now believed that H. erectus is a descendant of earlier hominins such as Australopithecus and early Homo species (e.g., H. habilis), although new findings in 2007 suggest that H. habilis and H. erectus coexisted and may be separate lineages from a common ancestor.

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 most of the Old World, reaching as far as Southeast Asia.

Fossilized remains 1.8 and 1.0 million years old have been found in Africa (e.g., Lake Turkana and Olduvai Gorge), Europe (Georgia, Spain), Indonesia (e.g., Sangiran and Trinil), Vietnam, and China (e.g., Shaanxi). H. erectus is an important hominin because it is believed to have been the first to leave Africa. However, some scholars believe that H. erectus is not the direct ancestor of modern H. sapiens.

A homo erectus skull, Tchadanthropus uxoris, discovered in 1961, is the partial skull of the first early hominid till then discovered in Central Africa, found in Chad during an expedition led by the anthropologist Yves Coppens. While some then thought it was a variety of the Homo habilis, the Tchadanthropus uxoris is no longer considered to be a separate species, and scholars consider it to be Homo erectus, and it is even argued that the skull is just a modern human, Homo sapiens sapiens, weathered by the elements to look like an australopithecine skull.

Description

Homo erectus has fairly derived morphological features and a larger cranial capacity than that of Homo habilis, although new finds from Dmanisi in the Republic of Georgia show distinctively small crania. The forehead (frontal bone) is less sloping and the teeth are smaller (quantification of these differences is difficult, however; see below). Homo erectus would bear a striking resemblance to modern humans, but had a brain about 75 percent (950 to 1100 cc) of the size of that of a modern human. These early hominines were tall, on average standing about 1.79 m (5 feet, 10 inches). The sexual dimorphism between males and females was slightly greater than seen in modern Homo sapiens with males being about 20-30% larger than females. The discovery of the skeleton KNM-WT 15000 ( Turkana boy) made near Lake Turkana, Kenya by Richard Leakey and Kamoya Kimeu in 1984 was a breakthrough in interpreting the physiological status of H. erectus.

Homo erectus would have been much stronger than modern humans, was the first hominid to hunt, use complex tools and care after weaker companions.

Usage of tools and general abilities

Homo erectus used more diverse and sophisticated tools than its predecessors. This has been theorized to have been a result of Homo erectus first using tools of the Oldowan style and later progressing to the Acheulean style. The surviving tools from both periods are all made of stone. Oldowan tools are the oldest known formed tools and date as far back as about 2.6 million years ago. The Acheulean era began about 1.2 million years ago and ended about 500,000 years ago. The primary innovation associated with Acheulean handaxes is that the stone was chipped on both sides to form two cutting edges. In addition it has been suggested that Homo erectus may have been the first hominid to use rafts to travel over oceans but however this idea is controversial within the scientific community.

Social aspects

Homo erectus (along with Homo ergaster) was probably the first early human species to fit squarely into the category of a hunter-gatherer society. Anthropologists such as Richard Leakey believe that H. erectus was socially closer to modern humans than the more primitive species before it. The increased cranial capacity generally coincides with the more sophisticated tool technology occasionally found with the species' remains.

The discovery of Turkana boy in 1984 has shown evidence that despite H. erectus's human-like anatomy, they were not capable of producing sounds of a complexity comparable to modern speech.

H. erectus migrated all throughout the Great Rift Valley, even up to the Red Sea. Early humans, in the person of Homo erectus, were learning to master their environment for the first time. Attributed to H. erectus, around 1.8 million years ago in the Olduvai Gorge, is the oldest known evidence of mammoth consumption (BioScience, April 2006, Vol. 56 No. 4, p. 295). Bruce Bower has suggested that H. erectus may have built rafts and traveled over oceans, although this possibility is considered controversial.

A site called Terra Amata, which lies on an ancient beach location on the French Riviera, seems to have been occupied by Homo erectus and contains the earliest (least disputed) evidence of controlled fire dated at around 300,000 years BP. There are also older Homo erectus sites in France, China, Vietnam, and other areas that seem to indicate controlled use of fire, some dating back 500,000 to 1.5 million years ago. A presentation at the Paleoanthropology Society annual meeting in Montreal, Canada in March of 2004 stated that there is evidence for controlled fires in excavations in northern Israel from about 690,000 to 790,000 years ago. Despite these examples, some scholars continue to assert that the controlled use of fire was atypical of Homo erectus, and that the use of controlled fire is more typical of advanced species of the Homo genus (such as Homo antecessor, H. heidelbergensis and H. neanderthalensis).

Classification

There has been a great deal of discussion concerning the taxonomy of Homo erectus (see the 1984 and 1994 volumes of Courier Forschungsinstitut Senckenberg), and it relates to the question whether or not H. erectus is a geographically widespread species (found in Africa, Europe, and Asia), or is it a classic Asian lineage that evolved from less cranially derived African H. ergaster.

While some have argued (and insisted) that Ernst Mayr's biological species definition cannot be used here to test the above hypotheses, we can, however, examine the amount of morphological (cranial) variation within known H. erectus / H. ergaster specimens, and compare it to what we see in different extant primate groups with similar geographical distribution or close evolutionary relationship. Thus, if the amount of variation between H. erectus and H. ergaster is greater than what we see within a species of, say, macaques, then H. erectus and H. ergaster should be considered as two different species. Of course, the extant model (of comparison) is very important and choosing the right one(s) can be difficult.

Descendants and subspecies

Homo erectus remains one of the most successful and long-lived species of the Homo genus. It is generally considered to have given rise to a number of descendant species and subspecies. The oldest known specimen of the ancient human was found in Africa.

• Homo erectus
  • Homo erectus yuanmouensis
  • Homo erectus lantianensis
  • Homo erectus pekinensis
  • Homo erectus palaeojavanicus
  • Homo erectus soloensis

Other species

• Homo floresiensis
• Homo antecessor
• Homo heidelbergensis
• Homo neanderthalensis
• Homo sapiens
  • Homo sapiens sapiens
• Homo rhodesiensis
• Homo cepranensis

The discovery of Homo floresiensis, and particularly its recent survival, has raised the possibility that numerous descendant species of Homo erectus may have existed in the islands of Southeast Asia which await fossil discovery. Some scientists are skeptical about the claim that Homo floresiensis is a descendant of Homo erectus. One theory holds that the fossils are from a modern human with microcephaly, while another one claims that they are from a group of pygmys.

Individual fossils

Some of the major Homo erectus fossils:

• Indonesia (island of Java): Trinil 2 (holotype), Sangiran collection, Sambungmachan collection, Ngandong collection
• China: Lantian (Gongwangling and Chenjiawo), Yunxian, Zhoukoudian, Nanjing, Hexian
• India: Narmada (taxonomic status debated!)
• Kenya: WT 15000 (Nariokotome), ER 3883, ER 3733
• Tanzania: OH 9
• Vietnam: Northern, Tham Khuyen, Hoa Binh
• Republic of Georgia: Dmanisi collection
• Turkey: Kocabas fossil

Some scholars consider specimens outside of Asia to be Homo ergaster. In other words, Homo erectus is an Asian lineage derived from Homo ergaster, which originated in Africa ca. 2.0 million years ago (Ma).