Homo Habilis

Homo habilis is a species of the genus Homo, which lived from approximately 2.3 to 1.4 million years ago at the beginning of the Pleistocene period. The discovery and description 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 the earliest known species of the genus Homo and the earliest known species to show novel differences from the chimpanzee and australopithid skulls. In its appearance and morphology, H. habilis is thus the least similar to modern humans of all species in the genus. Homo habilis was short and had disproportionately long arms compared to modern humans; however, it had a less protruding face than the australopithecines from which it is thought to have descended. H. 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 have often been found along with primitive stone tools, such as in Olduvai Gorge, Tanzania and Lake Turkana, and Kenya.

The jaw of Homo habilis is pulled under the brain, with smaller molars (though still much larger than in modern humans), and the skull is thinner, with a distinctive rounded shape, vertical sides and a small forehead above the brows. The first humans have arrived on the scene. A male habilis may have stood at around 1.3 meters and weighed 37 kilos, and females 1.2 meters and 32 kilos. However, some forms of habilis were apparently smaller, and may have stood little more than a meter tall.

Homo habilis has often been thought to be the ancestor of the more gracile and 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 may 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 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.

Homo Erectus

Homo erectus is an extinct Genus of homo who originated in Africa and spread out as far as China and Java—from the end of the Pliocene epoch to the later Pleistocene, about 1.8 to 1.3 million years ago. There is still disagreement on the subject of the classification, ancestry, and progeny of Homo erectus, with two major alternative hypotheses: erectus may be another name for Homo ergaster, and therefore the direct ancestor of later hominids such as Homo heidelbergensis, Homo neanderthalensis, and Homo sapiens; or it may be an Asian species distinct from African ergaster.

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 much of the Old World. Fossilized remains 1.8 and 1.0 million years old have been found in Africa (Lake Turkana and Olduvai Gorge), Europe (Georgia, Spain), Indonesia, Vietnam, and China.
Dutch anatomist Eugene Dubois, who was fascinated especially by Darwin's theory of evolution as applied to man, set out to Asia to find a human ancestor in 1886. In 1891, his team discovered a human fossil on the island of Java, Indonesia. Dubois described the species as Pithecanthropus erectus, based on a calotte (skullcap) and a femur like that of H. sapiens found from the bank of the Solo River at Trinil, in East Java. This species is now regarded as Homo erectus. This find became known as Java Man.

Throughout much of the 20th century, anthropologists debated the role of Homo erectus in human evolution. Nevertheless, early in the century, due to discoveries on Java and at Zhoukoudian, it was believed that modern humans first evolved in Asia. Only a few naturalists, such as Charles Darwin, predicted that humans' earliest ancestors were African: he pointed out that chimpanzees and gorillas, obviously human relatives, live only in Africa.

From 1950s to 1970s, however, numerous fossil finds from East Africa yielded evidence that the oldest hominins originated there. It is now believed that H. erectus is a descendant of earlier genera such as Ardipithecus and Australopithecus, or early Homo Genuses, such as H. habilis or H. ergaster. H. habilis and H. erectus coexisted for several thousand years, and may represent separate lineages of a common ancestor.