The Discovery of Ardipithecus Ramidus - Essay Example

ARDIPITHECUS RAMIDUS PALEOBIOLOGY AND COMPARISON WITH OTHER AUSTROLOPITHECUS By Hominid fossils dating backto the period before the emergence of Australopithecus have been scarce. However, the discovery of Ardipithecus ramidus means that researchers are now in a better position to understand earlier hominid paleobiology and other characteristics of evolution of the extant African ape. Ardipithecus ramidus had reduced canine and premolar concept, and consumed predominantly on plants. The evidence from this fossil remains provides a much sought link between the earliest Hominidae and the current man, revealing the origins of bipedality, orthogrady, diet, ecology and social behavior. The papers presented by the American Association of Advancement of Science (AAAS) provide an in depth analysis of the features of Ardipithecus ramidus as the missing link. The hominid fossils are approximately 4.4 million years old, and present close to 36 fragments, including parts of the skull and the pelvic girdle. The publications cover a number of themes, which include anatomical parts of the human evolution that show that Ardipithecus ramidus dwelt on land could climb trees as well, the habitat occupied by Ardipithecus ramidus based on thousands of fossils excavated at Arima as well as rock components, among others. The skull of Ardipithecus ramidus is of great importance as it enables the establishment of the link between ancient man and the present day man, in terms of brain size and shape of the skull and the face. Suwa et al. (2009) notes that Ardipithecus ramidus had a relatively smaller brain, of between 300 to 350 cubic centimeters, compared to its successor, Australopithecus which had a brain size of about 400cc. This brain size is just about that of female chimpanzees. Suwa et al. further observes that Ardipithecus ramidus had a smaller skull, an indication that it was not adapted to heavy chewing. However, it had a projecting muzzle typical of Sahelonthropus, a fete that gave it an ape-like appearance. Suwa et al further notes that the ridge above its eye socket is slightly different from that observed in chimpanzees, and that the lower part of its face does not project forward as is the case with chimpanzees. In addition, the bottom of the skull of Ar ramidus show that it had a short cranial base, as was the case with Australopithecus. These features point to the fact that despite the small brain Ardipithecus ramidus had, it was already developing hominid-like aspects. Furthermore, Andrea () confirms that even though Ardipithecus ramidus has many apelike features, it has a number of borrowed features as well, characteristics that make it a perfect link between apes and Australopithecines. The canines of Ardipithecus ramidus are almost similar to those of female chimpanzees, though with greater inclination towards those of Australopithecus (Kono et al, 2009). Studies on the molars of Ardipithecus ramidus show that they do not show enamel distribution patterns typical of their predecessors. Just like Australopithecus and other Miocene forms such as Dryopithecus, Ardipithecus ramidus lacks the thin occlusal fovea enamel, which means that it consumed diet containing less abrasive substances that required minimal chewing. This subtle analysis of teeth structure and modification help understand the probable social behavior of Ardipithecus ramidus. The last common ancestors of African apes and hominids had relatively low levels of canine and post canine teeth, which according to Kono et al. correlates to male philopatry and male-female co-dominance. The next concern in this link is the ability to walk upright. To achieve an upright posture, primates had to have a stronger pelvic girdle that could absorb all the tension from the upper body parts. Furthermore, upright posture required a stronger spine, which is not the case in even modern day chimpanzees. It is worth noting that no research gives an adequate explanation on exactly when the pelvic girdle evolved. However, research show that the transformation occurred much earlier, and that one of the oldest hominid pelvic girdles, that of Australopithecus afarensis shows that it had fully adapted to bipedality (Owen et al, 2009). Adapting to bipedality means that the primate had evolved a relatively stronger pelvic girdle, as well as a stronger spine to facilitate the upright posture. The discovery of Ardipithecus ramidus now offers a new insight into this transition. Owen et al. observes that despite the fact that the feet of Ardipithecus ramidus show that it climbed trees, it was able to walk upright while on the ground. He further notes that the gluteal muscles of Ardipithecus ramidus had undergone repositioning, and enabled it to walk without shifting its center of mass from either side. The shape of its ilium elaborates this development very well, and the appearance of the anterior inferior iliac spine, a special growth only found in hominids, further confirms the development of this trait. These changes enabled Ardipithecus ramidus to walk upright, and could as well run, though with slower speed compared to present day humans. This creature thus provides a critical adaptive transition to humans through the modification that resulted in pelvis and a lower limb that could allow the primate to walk upright while still capable of climbing trees. Nevertheless, the transition to upright posture remains a subject of discussion. Some researchers are of the opinion that the evidence provided by Ardipithecus ramidus is merely suggestive of bypedality but not conclusive. For instance, Gibbons (2009) notes that such concerns as the lack of placement of the knee over the ankle points to the likelihood of Ardipithecus ramidus walking while leaning to the side, and which if justified might lead to a unique form of bipedalism. However, regardless of these challenges, Ardipithecus ramidus provides a better link between humans and their ancestors. Furthermore, the fact that this primate did not have some of the specialized traits present in current chimpanzees confirms that there existed a transition point and which could as well be right in front of us in the form of Ardipithecus ramidus. Next in this analysis concerns the combination of propulsion and prehension in Ardipithecus ramidus. The human feet differ considerably with that of apes, a situation that greatly challenged researchers on the relationship between humans and apes. The discovery of Ardipithecus ramidus has provides a better explanation to the difference, and currently fills the missing link, thereby abolishing the longstanding stalemate. The feet of Ardipithecus ramidus have virtually no semblance to that of other primates. Unlike the African ape that is large and has limbs that can only grasp, and feet that are not easy to differentiate from their hands, Ardipithecus ramidus had relatively rigid feet that provided the necessary balance for walking and running. However, Latimer et al (2009) notes that the ability to walk in Ardipithecus ramidus was rather primitive since it had an opposable big toe. This implies that while other toes had undergone great modification to aid in upright posture and walking, the grasping big toe was retained for the same purpose, and thus enabling it to climb trees. This type of evolution ensured that while the African apes developed feet that allowed them to continue having the capability of grasping with high precision, the ancestor of modern man evolved feet that adapted to walking upright. Asfaw (2009) points out that Ardipithecus ramidus had an elbow joint that provided full extension but had no clear evidence of habitual suspension. Its ulna could undergo complete withdrawal and the thumb was moderately robust. The retention of such primitive characters relate to a mode of locomotion that is different from tree climbing; a clear indication that Ardipithecus ramidus never walked on knuckles. He further notes that the adoption of bipedality together with continued reduction in the size of the canine teeth forms the definitive characteristics of hominids. This implies that the last common ancestors of humans and apes were more primitive than was initially imagined. The habitat in which an organism lives also plays a vital role in its evolution patterns. A study of fossil remains of Ardipithecus ramidus reveals that the primate was predominantly a woodland dweller (White, 2009). He further notes that the wooded biotope in the Pliocene varied, and that the areas in which the hominid remains were found have soils rich in fossilized wood fragments, seeds, and animal fossils, which means that the Aramis area of Ethiopia, for instance, had more water than it has today. Fossils from the Aramis region are dominated by bone and dental fragments, an observation that leads to the conclusion that animals that inhabited the place were majorly carnivores. Thus, based on the available evidences from diverse geological and biological sources, Ardipithecus ramidus predominantly dwelt in woodland and grassland areas, feeding on plant material. It is worth noting that current information rally behind Ardipithecus ramidus as being the ‘chronospecies’ between Ardipithecus kadabba and Australopithecus anamensis. Two different hypotheses to back this up exist. The first hypothesis supports the idea of a probable existence of a form of speciation between the last Ardipithecus and the first Australopithecus. Secondly, it could be possible that Ardipithecus ramidus is a remnant of the earlier evolutionary split among the earliest hominids. Having the assumption that the ideas presented by white et al is true, then Ardipithecus ramidus is a ‘chronospecies’ i.e. it is a particular species that falls in a direct line of descent in the evolution of humans and which presumably did not have any side branches. In as much as some researchers may be inclined to think that this argument implies that paleontologists are examining different forms of the same specie occurring at different points in time rather ambiguous, there is the possibility that Ardipithecus ramidus represents a particular phase in evolution of hominids. The transition from Ardipithecus kadabba to Ardipithecus ramidus, then to Australopithecus could have as well descended in a linearly manner. Apart from concentrating on the mode of evolution of Ardipithecus ramidus, the fossils from this ancient man offers valuable insights that can be used to deduce a better understanding of how humans transitioned from Ardipithecus kadabba to Australopithecus. The features of Ardipithecus ramidus are quite impressive in comparison to other early hominids and even currently existing apes. Paleontologists and researchers alike ought to understand this as a transitional series in which it is possible to track the evolution of particular features. The presence of these fossils do not make previously available fossils less important, but rather offers a chance for their re-examination in comparison with the new ones in order to develop a more deductive conclusion on evolution of humans. References Asfaw, Berhane, Tim D. White, Yonas Beyene, Yohannes Haile-Selassie, C. Owen. 2009. Ardipithecus ramidus and the Paleobiology of Early Hominids ANDREA, A. J., & NEEL, C. (2011). World history encyclopedia. Santa Barbara, Calif, ABC-CLIO. Gibbons, Ann. 2009. A New Kind of Ancestor: Ardipithecus Unveiled. Kono, T. Reiko, Suwa, Gen, Scott W. Simpson, Berhane Asfaw, C. Owen Lovejoy and Tim D. White. 2009. Paleobiological Implications of the Ardipithecus ramidus Dentition Latimer, B., C. Owen Lovejoy, Gen Suwa, Berhane Asfaw and Tim D. White. 2009. Combining Prehension and Propulsion: The Foot of Ardipithecus ramidus. Owen, C., Lovejoy, Gen Suwa, Linda Spurlock, Berhane Asfaw and Tim D. White. 2009. The Pelvis and Femur of Ardipithecus ramidus: The Emergence of Upright Walking. Suwa, G., Berhane Asfaw, Reiko T. Kono, Daisuke Kubo, C. Owen Lovejoy and Tim D. White. 2009. The Ardipithecus ramidus skull and its implication for hiominid origin. White, D. T., Berhane Asfaw, Yonas Beyene, Yohannes Haile-Selassie, C. Owen. 2009. Macrovertebrate Paleontology and the Pliocene Habitat of Ardipithecus ramidus. Read More