Impact of Recently Discovered Hominins on the Understanding of Human Phylogeny - Research Paper Example

Impact of recently discovered hominins on the understanding of human phylogeny and biology The discovery of Australopithecus sediba and Homo floresiensis offer us clues to an important transition in our evolution. What we learn from these two discoveries is that about 6 millions year ago, when our ancestors began spending more time walking upright or in twos, their descendants evolved in various species, which have come to be referred to as hominids. For around 3.5 million years we are told that all hominids had the same basic kind of body whose characteristic included; a chimp-sized brain, elongated arms with curved fingers, a snout-like mouth and short legs that enable them to walk slowly on the ground. Scientists have called these early hominids as australopiths which is Latin for apes. Then starting around 2.3 million years ago, something curious happened. New hominids hit the scene, species that were subsequently christened homo, which is Latin for man. With the coming of these hominids, came the flattening of the snout and the shortening of the hook-like fingers of the australopiths, an evolutionary process that is assumed to have given birth to modern man (Homo sapiens). By approximately 1.8 million years ago, a species by the name Homo ergaster, which was about as tall as living humans, with stiff feet in its long legs that were only good for walking on the ground, hit the ground. Its brain on the other hand was only a third of our brain. This is how far the australopiths reached. What followed afterwards was the discovery of a group of species that were more man-like but with slight differences in their feature, species that have since assumed the name “Homo” which is Latin for man. A careful analysis of this narration reveals a missing link between the Australopiths (apes) and the homo (man). The big question that evolutionary scientists and paleoanthropologists have been trying for decades to interrogate is at which point and how did the australopiths turn into Homo. They have been pondering on where exactly did evolution took place and how did it unfold. It is only unfortunate that they have found relatively few hominid fossils from that period, which are not even complete skeleton but just scattered bones. It is only a consolation that Australopithecus sediba left behind two partial skeletons, which have accorded scientists a spectacular look at its anatomy and therefore assist in the understanding of the human phylogeny and biology. Based on the fossils’ anatomy, Dr. Berger, a renowned American paleoanthropologist who first stumbled upon the fossils, and his team have argued that Australopithecus is an australopith that is closely related to homo than any other fossils that has ever been discovered in the history of human evolution. The Australopithecus fossils that have come to be given the name “Australopithecus sediba” are from a boy and woman, both of which were found in the rolling grassland north of Johannesburg, which since the 1930s has been a preferred destination for fossil hunters (Kivell, 2011). One of the things that have made these fossils to qualify as new species of hominid, and an ancestor and a close relative of home sapiens (modern man) as such, is their mixture of both advanced and primitive anatomy that have been found in these fossils. The species sediba, which essentially translate to a wellspring or fountain in Sotho, is said to have strode in an upright gait with comparably long legs than those of a modern man (Evenne, 2011). Other similarities of sediba to the modern man can be found in its hips and bones that resemble greatly those of other species in the Homo genus, its small teeth and its face which is even more similar to the member of the Homo genus (Chiver, 2011). It greatest contrast with the modern man include its apelike arms, relatively primitive feet and a comparably “tinier brain” than that of Australopithecus. According to evolutionary scientists, sediba must have descended from Australopithecus Africanus (Carlson, et al, 2009). At a teleconference, Dr. Berger described Australopithecus sediba as a probable ancestor of Homo erectus, an immediate precursor of Homo sapiens, or a very close “side branch” of the same that however did not lead to modern human (Evenne, 2011). According to him (Berger), Australopithecus sediba is a “time machine” in the evolutionary process. Rick Potts, of the Human Origins Program at Smithsonian, said of the fossils that “they are an intriguing mosaic of features that take you back to the combining and recombining of characteristics and the experimentation and tinkering, that characterize evolution (Chiver, 2011).” Dr. Berger and the entire discovery team of Australopithecus sediba have interpreted the fossils as a formerly unclassified species of sophisticated Australopithecus “with suggestions of the genus Homo.” Berger and his team aside, what is however very clear as far as Australopithecus sediba is in helping us understand human phylogeny and biology is that other than being the earliest direct ancestor of modern man yet to be discovered, it mostly hints that humanity first bipedal steps, or rather first steps, must have taken place in South Africa instead of East Africa as had earlier been thought (Kivell, 2011). In fact, it gives new and fascinating insight into the evolution of both humanity’s brain and anatomy structure. Of particular interest is the way Australopithecus sediba has been widely touted as the missing link between humanity and apes. This has emanated from its features most of which have made it to be referred to as a “fossil that is neither completely an ape nor completely a man but lying somewhere between the two (Chiver, 2011).”The discovery of this fossil having had a small brain might be consistent with Australopithecus (an ape) genus, however the organization of this small brain has been found to be very similar to that of human. In this regard, I am referring to the organization of the frontal lobe of this fossil vis-a-viz that of human. What this similarity portends is that contrary to what was previously thought, organization and brain size within human evolution might not have been an instantaneous change (Evenne, 2011). One of the frequently asked questions in evolutionary biology when it comes to the long list of the so-called transitional fossils is where exactly does the apes stops and human begins? Some would like to convince us that Australopithecus is the link between the Man and the ape, while others would like to convince us that Homo habilis is the link between the two (man and ape). However the Latin name Australopithecus and Homo habilis (meaning ‘Southern Ape’ and ‘handy man’ respectively) bears testimony that one of them is a man while the other is an ape and none comes close to the transition of the two. A serious campaign has also been launched seeking to have all modern apes reclassified into the Homo genus, one of the reason being bandied around by the supporters of this reclassification being that they are so similar to human. This therefore shows just how arbitrary the line between apes and humanity has become. However, bearing the fact that Australopithecus sediba is later than Australopithecus Africanus, while sharing many features with early Homo and especially Homo habilis, there is no doubt that it is the missing link between the two. In supporting the idea that Australopithecus sediba is the missing link between human and apes, Dr. Berger is reported to have explained that its small but advanced brain, a very evolved hand that has long thumbs like those of a human, a very modern pelvis but an ankle and foot shape never seen before in any hominid species, combines both human and ape features. Although Australopithecus sediba fossil were initially dated over 2 million years ago they have since been re-dated to around 1,977 years when it is believed the genus Homo emerged, further reinforcing the ideas that they were the missing link between man and ape (Carlson, et al, 2009). Evolution scientists have also been split right in the middle on whether Australopithecus sediba should be assigned to the Australopithecus or a Homo, which is also a manifestation of the near unanimity of the idea that these fossils must have been the missing bridge between a man and the ape (Carlson, et al, 2009). Majority of researchers believe that the pelvis of the Australopithecus sediba is the one feature that shows the strongest connection toward the commencement of an evolutionary change to the Homo. Researchers have constantly linked the larger brain structure that exists between the two. However, even with the diminutive brain size and cranial structure of Australopithecus sediba, the pelvis structure has moved closer to that of Homo from the previous Australopithecus’ structure. According to Berger, the discovery of Australopithecus sediba is significant in that it enables us to understand human evolution and particularly, what they revealed to us about early hominids’ abilities in making stone tools (Kibii, et al, 2009). The dexterity of the hands of the Australopithecus sediba has been one of the points of convergence with the rest of the homo genus, and especially Homo habilis (handy man). The analysis of fossils of Australopithecus sediba reveals that it was capable of precision grip just as was the case with Homo habilis, a feature that enabled it to carve stone tools. Nicknamed “Hobbit,” the hominid species, Homo floresiensis still remaining the most latest discovered hominid species. Unlike the remains of Australopithecus sediba that were discovered in Africa (South Africa to be specific) those of Homo floresiensis were discovered in the Island of Flores, Indonesia. The analysis of this hominid species reveals that it existed between 95,000 to 17,000 years ago in this Island of Flores and stood about 3 feet 6 inches tall (William et al, 2009). Other characteristics that have been found to have been exhibited by this hominid species include an extremely tiny brain (400mL), shrugged-forward shoulders, large teeth despite their small size, receding forehead, no chin, relatively large feet probability to compensate for their short legs (Weston et al, 2009). Other revelations that can be made from the Homo floresiensis fossil is that it must have used fire, must have used stones tools, must have hunted large rodent and small elephant, and lastly, had to coexist with predators like giant kamondo dragon (William et al, 2009). One of the reasons that have been advanced to explain the diminutive stature and small brain of Homo floresiensis is the dwarfism that has since been associated with the Island of Flores at the time. A manifestation of this dwarfism in the Island of Flores can be found in other species at the Island. The now extinct pygmy elephants whose fossils have been found in the Island are said to have exhibited similar adaptation. Even the smallest known species of the now extinct Stegodon and Homo Elephant were found in the Island of Flores which further reinforces the idea that the island generally predisposed species there to dwarfism – an evolutionary process resulting from an extended isolation on a tiny island like the Island of Flores with limited resources and no predators (William et al, 2009). An examination of the extinct Madagascan hippos has also been used to explain the diminutive brain size that has been found in dwarfed Homo floresiensis and other previous species (Stegodon and Homo Elephant) that have since been found in the Island of Flores. According to these museum scientists, dwarfed mammals on Islands evolved much smaller brains as compared to their body. After a thorough study of nearly three thousand years old dwarf hippos, it was found that the brain sizes of these extinct mammals was at least 30% smaller than would be expected after scaling down their mainland African ancestors to their body size. Applying this model to a typical Homo erectus, the resulting brain capacity is comparable to that of Homo Floresiensis. Therefore Homo floresiensis might have had a smaller brain because it lived on an Island. According to Dr. Eleanor Weston, a Natural History Museum paleontologist, Homo floresiensis must have been a dwarf resulting from its Homo erectus ancestors who were isolated in the Island of Madagascar many years ago. This is a serious finding and an important breakthrough in the understanding of human phylogeny and biology. In fact, though this phenomenon of dwarfism in large mammals is known and documented in the Island of Flores, it has never been better demonstrated before as has been the case with the discovery of Homo floresiensis. Several scientists are interrogating the possibility that the ancestors of Homo floresiensis might have been small when they first arrived in the Island of Flores. Majority others are busy drawing the line between the small statured of Homo floresiensis and that of the current inhabitant of this region, thereby greatly increasing the understanding and literature of the human phylogeny and biology. In fact, there is considerable scientific debate raging on whether Homo floresiensis represent the modern man, although with a growth disorder or a disease. In drawing the line between Homo floresiensis and the modern man scientists have argued that the small body size might have been an adaptation that might have been informed by the need to survive in the context of the limited resources (Weston et al, 2009). Normally, it is considered advantageous for animals that have been isolated on Islands with hostile environment to not only become dwarfs, but also reduce considerable their brain size. In explaining the small size of Homo floresiensis, Dr. Weston argues that the brain is a very costly organ that consumes a lot of energy. Whatever the explanation that might be advanced in explaining the small size the fact remain that leaving in an Island with a hostile environment played a major role in its evolution. Another feature of this hominid is the stone tools majority of which bear a great resemblance to those tools that have been found not only in the whole of island of Flores but throughout the human evolutionary career, like Oldwan tools and Lower Paleolithic tools in Africa and Asia respectively. Just like other previous species, Homo floresiensis selectively hunted animal for food as can be evidenced by the hundreds of bones fragments belonging to stegodon (an extinct elephant type), some with butcher marks, that have been found within occupation layers of Homo floresiensis (William et al, 2009). Scientists are also interrogating exactly how Homo floresiensis is related to other species in the genus Homo. Some of the questions guiding this debate include; how exactly did Homo floresiensis evolve from a previous population of Homo erectus; did it evolved from any of the smaller species and especially those that have been discovered in modern-day Georgia (republic of Dmanisi) or possibly any of the earlier species of the Homo genus (Weston et al, 2009). However, what is not in doubt or a subject of debate is the fact that Homo floresiensis is a valid taxon and a human species that is slightly distinct from the modern man (Homo sapiens) (Weston et al, 2009). This information has been greatly helpful in filling the lacuna that exists in our understanding of the human evolutionary development. In a nutshell, the two fossils have been extremely helpful in enhancing the understanding of human phylogeny and biology and especially filling the gaps that have existed on the link between man and ape. In this regard, I am referring to the sharing of features of both Homo (man) and australopiths (ape) of the Australopithecus sediba which has been translated by evolutionary scientists to mark the transition between man and ape. Homo floresiensis on the other has directed the focus of the evolutionary community on the phenomenon of dwarfism which has greatly enabled us to draw parallels between australopiths and Homo despite their size. This is no doubt a great discovery especially because variation in size has been a major determining factor in the classification of hominids. Works Cited Carlson, J, Stout, D, Jashashvili, T, Ruiter, D, Tafforeau, P, Carlson, K, Berger, L, The Endocast of MH1, Australopithecus Sediba, 2009, Science, 333(6048): 1402-1407 Chiver, T, Australopithecus Sediba: We Can Stop calling it a ‘missing’ Link, The Telegraph, 10th September 2011 Evenne, B, Melborne Researchers Uncover Missing Link, Herald Sun, 9th September 2011 Kibii, M, J, Churchill, E, S, Schid, P, Carlson, J, K, Reed, D, N, Ruiter, J, D, & Berger, R, L, A Partial Pelvis of Australopithecus Sediba, 2009, Science, 333(6048): 1407-1411 Kivell, L, T, Kibii, M, J, Churchill, E, S, Schmid, P, Berger, R, L, Australopithecus Sediba Hand demonstrates Mosaic Evolution of Locomotor and Manipulative Abilities, 2011, Science, 333 (6048): 1411-1417. Weston et al, Insular Dwarfism in Hippos and a Model for Brain Size Reduction in Homo Floresiensis, Nature, 2009, 459 (7243), 85 Retrieved on 25th November 2011 from Read More