Hominid Evolution: From Africa to Homo Ergaster
The Hominids: An Evolutionary Overview
The hominids are a group of non-arboreal primates whose origin is in Africa for at least several million years. A key characteristic is moving into a bipedal position. This conditions the situation of the foramen magnum at the base of the skull, through which the spinal cord passes to the backbone. On each side and downward facing are the occipital condyles: the double articulation of the skull to the backbone. Their palate is U-shaped, surrounded with a dental arch and small teeth. Their skull houses a large cerebrum. This increase is related to a diet with high energy content because the brain is an organ that spends a lot of energy, requiring locomotor and digestive system adaptations, and increased social complexity.
Ardipithecus ramidus: The Oldest Known Hominid
Ardipithecus ramidus is the oldest hominid known well. Fossils dating back 4.5 million years have been found. While it has many ape-like features, it is doubtful that bipedalism had become fully functional. A. ramidus gave rise to A. anamensis.
Australopithecus anamensis: Apelike Features and Bipedalism
Australopithecus anamensis had an apelike appearance, though its hominid features, such as bipedalism and thick tooth enamel, allowed it to eat hard food.
Australopithecus afarensis: Prognathism and Bipedal Gait
Australopithecus afarensis had a face with a protruding nose (prognathism) and a prominent bony ridge along the axis of the skull (sagittal crest). Its brain capacity was slightly higher than that of chimpanzees. The pelvis and lower limbs have a human aspect, which indicates bipedal gait.
Later Australopithecus afarensis: Anatomical Trends
Later A. afarensis hominids show two anatomical trends in conjunction with bone formation, mainly on the skull and the jaw: a more graceful form, represented by A. africanus, and a more robust form, represented by Paranthropus: P. aethiopicus, P. boisei, and P. robustus. These showed the axis of the skull traversed by a prominent sagittal crest. Unlike the australopithecines, which were omnivores and scavengers, the Paranthropus were vegetarians who ate hard food (except for P. robustus), as evidenced by their powerful jaws. In Ethiopia, a new species has been found, which is considered a. garhi, evolutionarily related to the primitive African Homo, given its teeth and its extended lower limbs.
Homo habilis: The First Toolmakers
Homo habilis: The first Homo remains have been found. Its name comes from the fact that, along with their fossils, in the Olduvai Gorge (Tanzania), a number of very primitive stone tools were found, which are supposed to have been created by them (the ability that makes them human). Its skull was much greater than that of Australopithecus. Despite its marked prognathism and supraorbital ridge marking, its teeth were similar to humans (it was adapted to crushing). It is assumed that Homo habilis began to lose body hair. In their diet, more diversified than that of Australopithecus, dominated by hard foods of plant origin, they were not systematic meat eaters (product of carrion or hunting).
Homo ergaster: Migration Out of Africa
Homo ergaster: The first fossils were discovered on the shores of Lake Turkana and Olduvai Gorge. Its skull, bigger and wider than that of H. habilis, showed well-developed supraorbital arches and small teeth adapted to a diet based on meat, animal fat, and other soft foods. The skeleton was very similar to modern humans. In its helpful, and worked hand axes teardrop, it is found that the end result was a form preconceived by its manufacturer. In its deposits, bones have been found with marks of stone tools, which testifies that meat-eating was common. It is assumed that H. ergaster were the first humans who left Africa, a minimum of 1.9 million years ago.