Homo habilis

Homo habilis (IPA ) ("handy man", "skillful person") is a species of the genus Homo, which lived from approximately 2.6 million to at least 1.4 million years ago at the beginning of the Pleistocene. The definition of this species is credited to both Mary and Louis Leakey, who found fossils in Tanzania, East Africa, between 1962 and 1964. 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. It is thought to have descended from a species of australopithecine hominid. Its immediate ancestor may have been the more massive and ape-like Homo rudolfensis. Homo habilis had a cranial capacity slightly less than half of the size of modern humans. Despite the ape-like morphology of the bodies, H. habilis remains are often accompanied by primitive stone tools (e.g. Olduvai Gorge, Tanzania and Lake Turkana, Kenya).

Homo habilis has often been 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. However, in 2007, new findings suggest that the two species coexisted and may be separate lineages from a common ancestor instead of H. erectus being descended from H. habilis.

Findings
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 demonstrated australopithecine-like body with a more human-like face and smaller teeth. Compared to australopithecines, H. habilis's brain capacity of 590 and 650 cc was on average 50% larger than australopithecines, but considerably smaller than the 1350 to 1450 cc range of modern Homo sapiens. These hominins were smaller than modern humans, on average standing no more than 1.3 m (4'3") tall.

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 as "Australopithecus habilis".

KNM ER 1813
KNM ER 1813 is a relatively complete cranium which dates 1.9 million years old, discovered at Koobi Fora, Kenya by Kamoya Kimeu in 1973. The brain capacity is 510cc, not as impressive as other early specimen and forms of Homo habilis discovered.

OH 7
OH 7 dates 1.75 million years old and was discovered by Jonathan Leakey on November 4, 1960 at Olduvai Gorge, Tanzania. It is a lower jaw complete with teeth and due to the size of the small teeth; researchers estimate this individual had a brain volume of 363cc.

OH 24
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. The brain volume is just under 600cc; also a reduction in a protruding face is present compared to members of more primitive Australopithecines. Twiggy was found in a distorted matrix with a coating of limestone rock.

KNM ER 1805
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 belongs 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 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 sister species (or 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 scimitar-toothed predatory cat the size of a jaguar. H. habilis used tools primarily for scavenging, such as cleaving meat off of carrion, rather than defense or hunting. 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.

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 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.

Stratification and expansion
The evolution of Homo habilis is associated with the species' movement from the central Saharan region of Africa into the more demanding, yet resourceful habitats of Europe and to a lesser extent Asia. The major developments which contributed to this phenomena were the greater knowledge and skill with which Homo habilis crafted the rock blade, increasing knowledge about climate and how to adapt accordingly and the evolution of the voice-box which allowed greater co-ordination in hunting than was hitherto possible. Homo habilis, due perhaps to many years of adaptation, were able to create flint blades with 4 inches of cutting blade, this finer blade was strong enough to advance Homo habilis from scavenger to hunter. After many thousands of years of adaptation, humans were eventually able to accumulate enough information about the climate to adapt accordingly, building fires and wearing thick hides to stave off the cold. The evolution, or more so the moving of the voice box from the top of the throat to the bottom allowed a greater variety of speech required to co-ordinate and communicate during hunts. All of these evolutionary measures allowed Homo habilis to exploit the harsher climates of Asia and the borders of Europe. The western and central region of Europe was not settled by humanoids until the time of Homo erectus.