Fossils of Homo Species

Fossils of Homo Species
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Fossils of Homo Species
According to scientists, archaeologists, historians, anthropologists among other scholars, human beings evolved gradually through numerous stages to their present stage of Homo sapiens sapiens. Human evolution can be defined as the evolutionary history of genus Homo that includes the emergence of Homo sapiens not only as a unique category of hominids but also as a distinct species. Fossils and fossil evidence for that matter provides proofs to scholars and other interested people in human evolution that human species had existed in earlier years in different forms. Fossils also provide the evidence that human species had existed in various activities and how they adapted to their environments during different stages of evolution. Various fossil specimens or tool industries include those of Australopithecus, Acheulin, Aridpithecus, Upper Palaeolithic tool industries, Mousterian, Oldewan, and Paranthropus among others. In this discussion, the fossils of Australopithecus will be discussed.
Australopithecus is a term derived from Latin word australis which means southern and Greek word pithekos which means ape. It is a genus of hominids that is now extinct. Leakey (1994) argues that Australopithecus genus evolved in eastern Africa around 4 million years ago before spreading later on throughout the African continent and eventually becoming extinct around 2 million years ago. Leakey goes further to note that during this time there were different forms of Australopithecus and they included Australopithecus anamensis, Australopithecus afarensis, Australopithecus sediba, and Australopithecus africanus. According to Lewin (1999), Australopithecus is made up of the aforementioned species that fall under two general types; that is, robust forms and gracile forms. Numerous findings have suggested that robust forms existed from 4- 1 million years ago while the gracile forms persisted from 4 - 2 million years ago. Most archaeologists and paleontologists hold that the australopiths formed a critical part in the evolution of human kind. To support their position, they argue that one of the australopith species eventually evolved into the Homo genus in Africa in a period around 2 million years ago which within it contained species such as Homo ergaster, Homo habilis and eventually the modern species of man, Homo sapiens sapiens Lewin (1999).
In regard to the features associated with Australopithecus, Scarre (2005) explains that their brains were roughly 35% of the size of that of a modern human brain. He adds that they were 3 feet 10 inches to 4 feet 7 inches tall. Besides, among several Australopithecus variations there was a significant degree of sexual dimorphism with that of males being larger than those of females. Regarding their diet, the study of Australopithecus fossil teeth have suggested that they were largely frugivorous. They had a massive, thickly- enameled molar teeth adapted to diet of tough plant material. Their diet composed mainly of vegetables, tubers, and fruits. Also, trace element studies of the calcium/ strontium ratios among australopith fossils suggest that there was possibility of animal consumption Scarre (2005). This species was a bipedal ape. Bipedalism arose before the evolution of large volumes of brains or intelligence associated with humans. They did not walk in the human manner but loped along similar to chimpanzee. Their naturally upright stance is confirmed by occipital condyles and foramen magnum being set far forward and the neck muscles attach low down on the back.
As has been noted, Australopithecus genus is made up of several species that fall under two general types namely; robust and gracile forms. The differences in type between the gracile and robust australopithecines are viewed in terms of their adaptive profiles. According to Lewin (1999), the facial and cranial morphology of these two types shows different diets and thus separate niches. The differences thus explain the co- evolution of these two groups on the same landscapes for 2 million years. Robust forms` adaptive profiles show reliance on a diet of gritty and fibrous vegetation. The robust mandible, heavy bone architecture, and the relatively large cheek teeth serve as convincing evidence for a diet that needs intense mastication. As noted, these forms existed between 4 and 2 million years ago. Throughout their existence, they are sympatric with the gracile forms and later on with early Homo. Robust species are: A. robustus, A. boisei, and A. aethiopicus. On the other hand, gracile forms` adaptive profile includes the generalist advantage of human species Scarre (2005). Essentially, they specialized in generalism rather than in hard- to- process herbivorous food. They lacked bony crests for heavy chewing muscles; they had smaller cheek teeth with an emphasis on the anterior dentition, and the general lighter appearance. All these characteristics indicate that this hominid was having a more opportunistic approach to carving out a niche for one`s self. Leakey (1994) notes that these forms appeared 4 million years ago, the same time that their counterparts robust appeared. However, they persisted until 2 million years ago. Gracile species include: A. afarensis, A. africanus, and A. anamensis.
The first fossil of Australopithecus to be discovered and documented was a three- year old Australopithecus africanus fossil which was discovered in a lime quarry at Taung, South Africa White et al. (2006). The specimen discovered was studied by Raymond Dart, an Australian anatomist, who was then working at the University of Witwatersrand in Johannesburg as an anatomy professor. He published his findings in the Journal of Nature in February 1925. Dart observed that the fossil contained several humanoid features and he therefore came to conclusion that this specimen represented an early human ancestors. According to Dart, his conclusion was based on the fact that the position and shape of the base of the brain cast was nearly similar to that of humans. He further observed that the foramen magnum was pointing downward and was close to the central balance point of the skull. Besides, the canine teeth were somehow short. All these traits he concludes were much more like humans` than apes. As White et al. (2006) explain, ten years later Dart and Robert Broom set about to search for more early hominid specimens, and they managed to find A. africanus remains in several sites in addition to fossils of a species that Broom termed as Paranthropus. Broom was a paleontologist who spent the rest of his life searching for early human species fossils after retiring as a medical doctor. He discovered A. robustus in 1936 while he was excavating in Sterkfontein cave in South Africa. He found more africanus remains in Kromdraai cave. The fossils that he found were more muscular and had larger bo...