Homo habilis

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How to read a taxoboxHomo habilis
Fossil range: Pliocene-Pleistocene
KNM ER 1813 discovered at Koobi Fora
KNM ER 1813 discovered at Koobi Fora
Scientific classification
Kingdom: Animalia
Phylum: Chordata
Class: Mammalia
Order: Primates
Family: Hominidae (Great Apes)
Genus: Homo
Species: H. habilis
Binomial name
Homo habilis
Leakey et al, 1964

Homo habilis (IPA /ˈhoʊmoʊ ˈhæbələs/), meaning "handy man," or "skillful person," is the oldest known species of the genus Homo, to which human beings belong. Homo habilis lived from approximately 2.5 million to 1.5 million years ago, appearing first in the late Pliocene or early Pleistocene. It is considered to have diverged from the Australopithecines.

Some scientists have proposed moving this species out of the genera Homo and into Australopithecus. Fossil findings are very fragmentary. Kreger (2005) concludes that "No two researchers attribute all the same specimens as habilis, and few can agree on what traits define habilis, if it is a valid species at all, and even whether or not it belongs in the genus Homo or Australopithecus."

In the view of theologians, who believe that human beings are special creations of God, Homo habilis provided the foundation for modern humans. Together with its precursors, such as Australopithecus, it can be seen as fulfilling stages required in the course of creating the human physical aspect. (It is also possible that they were not direct ancestors, but rather had a role in preparing the environment for modern humans.)

Contents

Overview

Homo habilis is one of the earliest known hominids. The term "hominid" technically refers to any member of the biological family Hominidae (the "great apes"), a group of primates that includes extinct and extant humans, chimpanzees, gorillas, and orangutans. However, the original use of "hominid" was restricted to humans and their extinct relatives; that is, those more closely related to humans than the great apes. This original definition of hominid remains popular with many anthropologists and lay people.

Homo habilis is arguably the first species of the Homo genus to appear. In its appearance and morphology, H. habilis was the least similar to modern humans of all species to be placed in the genus Homo (except possibly Homo rudolfensis). Homo habilis was short and had disproportionately long arms compared to modern humans; however, it had a reduction in the protrusion in the face. These hominins were smaller than modern humans, on average standing no more than 1.3 m (4'3") tall. H. habilis's brain capacity was on average 50 percent larger than australopithecines, but considerably smaller than the 1350 to 1450 cc range of modern Homo sapiens.

Another fossil hominid from about two million years ago was found that was originally described as Homo habilis, but was eventually separated, with the larger-brained specimens assigned to H. rudolfensis and the name habilis restricted to the smaller specimens. Homo habilis brains measured only 450, 500, and 600 cc, overlapping Australopithecus, while Homo rudolfensis were strikingly larger, from 700 to 900 cc (Mayr 2001). Ironically a finding of a specimen now assigned as H. rudolfensis (KNM ER 1470), but then considered H. habilis, is credited with leading to acceptance of habilis as a distinct species (Smithsonian NMNH 2007).

Hominid fossil findings are actually quite fragmentary (see human evolution and the accounts of habilis findings below), and thus interpretations are subject to change. The small size and rather primitive attributes have led some experts (Richard Leakey among them) to propose excluding H. habilis from the genus Homo, and renaming them as Australopithecus habilis. Mayr states that "Homo habilis is now considered a late species of Australopithecus."

Homo habilis is thought to have descended from a species of australopithecine hominid, and its immediate ancestor may have been the more massive and ape-like Homo rudolfensis. Despite the ape-like morphology of the bodies, H. habilis remains are often accompanied by primitive stone tools (for example, at Olduvai Gorge, Tanzania, and Lake Turkana, Kenya).

Homo habilis is thought to be the ancestor of the lankier and more sophisticated, Homo ergaster, which in turn gave rise to the more human-appearing species, Homo erectus. Debates continue over whether H. habilis is a direct human ancestor, and whether all of the known fossils are properly attributed to the species.

Mayr (2001) notes that the Homo genus, a far advanced hominid, appeared suddenly in eastern Africa. He finds this quite puzzling, as H. rudolfensis does not seem to have descended from any known Australopithecus species in eastern and southern Africa, and if it came from Australopithecus species elsewhere (western and northern Africa), then no fossils have been found so far.

Findings

Richard Leakey describes the discovery and naming of the first habilis in The Making of Mankind (1981). It was unearthed by anthropologist Louis Leakey's son, Jonathan Leakey, at Olduvai Gorge, Tanzania, on November 4, 1960, and was called at first "Jonny's child." It was announced in 1964. Richard says that Louis named the fossil for its "ability to make tools" and that habilis means "skillful." By another account, Louis Leakey solicited a name from Raymond Dart, which Phillip Tobias translated as "handyman." Later, it became OH 7 described under "famous specimens," below. The definition of this species is credited to both Mary and Louis Leakey, who found fossils in Tanzania, East Africa, between 1962 and 1964.

This first specimen, OH 7, is the type specimen of Homo habilis. The specimen consists of "a nearly complete left parietal, a fragmented right parietal, most of the mandibular body (including thirteen teeth), an upper molar, and twenty-one finger, hand, and wrist bones" (Kreger 2005).

One set of fossil remains (OH 62), discovered by Donald Johanson and Tim White in Olduvai Gorge in 1986, included the important upper and lower limbs. An older (1963) finding from the Olduvai site found by N. Mbuika had included a lower jaw fragment, teeth, and upper mandible possibly from a female dating 1.7 million years old. The remains from 3 skeletons (McKie 2000) demonstrated an australopithecine-like body with a more human-like face and smaller teeth.

Famous specimens
  • KNM ER 1813 is a relatively complete cranium which dates to 1.9 million years old, discovered at Koobi Fora, Kenya by Kamoya Kimeu in 1973. The brain capacity is 510 cc, not as impressive as other early specimen and forms of Homo habilis discovered. However, Kreger (2005) notes that some scientists conclude that KNM-ER 1813 is a near perfect Homo erectus, except for its small brain and size, and that it could be an erectus that was small or even be a Homo ergaster.
  • OH 7 dates to 1.75 million years old and was discovered by Jonathan Leakey on November 4, 1960, at Olduvai Gorge, Tanzania. It is the type specimen. It has a lower jaw complete with a number of teeth and the left parietal is nearly completed. The brain size attributed to this specimen (assumed to be a young boy) ranges from 590-710 cc (Kreger 2005).
  • OH 24 (AKA "Twiggy") is a roughly deformed cranium dating 1.8 million years old, discovered in October 1968, at Olduvai Gorge, Tanzania by Peter Nzube. It was found in a very fractured state, cemented in limestone rock, and had to be reconstructed, but over 100 small fragments could not be assigned a location in the reconstruction (Kreger 2005). An estimate of 590 cc is given for the brain volume (Kreger 2005). A reduction in a protruding face is present compared to members of more primitive Australopithecines.
  • KNM ER 1805 is a specimen of an adult H. habilis made of 3 pieces of cranium dating 1.74 million years old from Koobi Fora, Kenya. Previous assumptions were that this specimen belonged to H. erectus based on the degree of prognathism and overall cranial shape.

Interpretations

Homo habilis is thought to have mastered the Olduwan era (Early Paleolithic) tool case, which utilized stone flakes. These stone flakes were more advanced than any tools previously used, and gave H. habilis the edge it needed to prosper in hostile environments previously too formidable for primates. Whether H. habilis was the first hominin (member of the tribe Hominini: extinct and extant chimpanzees and humans) to master stone tool technology remains controversial, as Australopithecus garhi, dated to 2.6 million years ago, has been found along with stone tool implements at least 100,000-200,000 years older than H. habilis.

Most experts assume the intelligence and social organization of H. habilis were more sophisticated than typical australopithecines or chimpanzees. Yet despite tool usage, H. habilis was not the master hunter that its descendants proved to be, as there is ample fossil evidence that H. habilis was a staple in the diet of large predatory animals such as Dinofelis, a large predatory cat similar to a leopard. H. habilis seems to have used tools primarily for scavenging, such as cleaving meat off of carrion, rather than defense or hunting.

Homo habilis co-existed with other Homo-like bipedal primates, such as Paranthropus boisei, some of which prospered for many millennia. However, H. habilis, possibly because of its early tool innovation and a less specialized diet, became the precursor of an entire line of new species, whereas Paranthropus boisei and its robust australopithecine relatives disappeared from the fossil record.

The classification of H. habilis into the Homo genus is controversial. Like Homo rudolfensis, H. habilis lacked many of the things that were unique to later hominins, such as slim hips for walking long distances, a sophisticated sweating system, narrow birth canal, and legs longer than arms. Such traits as noticeable whites in the eyes, smaller hairs resulting in exposed skin, and a naked appearance remain theoretical. Despite larger brains than earlier species, and bipedal locomotion, many scientists think H. habilis and its close relative H. rudolfensis to be more ape-like, and not properly belonging in the Homo genus.

References

  • Gallant, R. A. 2000. Early Humans. New York: Benchmark Books. ISBN 0761409602.
  • Kreger, C. D. 2005. Homo habilis: Introduction. Archaeology.info. Retrieved March 4, 2007.
  • Leakey, R. E. 1981. The Making of Mankind. Elsevier-Dutton Publishing Company, Inc. ISBN 0525150552.
  • Mayr, E. 2001. What Evolution Is. New York: Basic Books. ISBN 0465044255.
  • McKie, R. 2000. Dawn of Man: The Story of Human Evolution. New York: Dorling Kindersley Pub. ISBN 0789462621.
  • Smithsonian National Museum of Natural History (Smithsonian NMNH). 2007. Homo habilis. Smithsonian Institution. Retrieved March 4, 2007.

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