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Laetoli

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An Appraisal of the Historic Site of Laetoli
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An Appraisal of the Historic Site of Laetoli
Background
Laetoli is a famous excavation site that was discovered in Tanzania. The site is famous for the fossil remains of Plio-Pleistocene hominids Australopithecus afarensis. The hominid footprints were found to be preserved in the volcanic ashes. The exact site is located 45 kilometers away and south of Olduvai Gorge. The site was discovered by Mary Leakey, an archeologist during 1976. The entire excavations were completed in 1978. The hominid footprints provided the first conclusive evidence regarding the presence of bipedal mammals in the Pliocene era. The era traces back to 3.7 million years ago, and bipedal movement was not at all speculated. The fossils of Ardipithecus ramidus confirmed the presence of bipedalism during such period. The bipedalism was confirmed from the footprints. Moreover, other discoveries and findings in the excavations at Laetoli included the animal skeletal remains and hominin fossils. Earlier in the history of evolution, it was predicted that enlarged brains were earlier to develop before bipedalism in man. However, this excavation proved the earlier speculations wrong and it was concluded by various scientists and researchers that bipedalism was earlier to develop compared to enlarged brain in humans or mammals. The site became so important from the perspective of evolution that it was visited numerous times in between 1998 and 20051.

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During such revisits and further excavations the researchers discovered Paranthropus aethiopicus at a site outside the modern day Turkana Basin. The site was first referred to Louis Leakey during 1935, by a man called Sanimu. Louis Leakey was an archeologist and visited the place. He discovered and collected some canine tooth and classified them as primates that were not humans. However, during 1979, the scientists’ P. Andrews and T. White confirmed that the canines were not of non-human primates and they were from the first primate hominids. The site was visited and extensively studied during 1938 and 1939 also. At that time a German archeologist named Ludwig Kohl-Larsen excavated various premolars, incisors and molars of various hominin remains. However, searches from 1939 to 1959 revealed no newer findings and remains. The excavations were discouraged as no new hominin or hominin traits were isolated. It was in the year 1974 when a scientist named George Dove visited the site and collected new evidence of hominin molars from the site. This instigated and encouraged Mary Leakey to excavate the site further during 1976 and 1978. This marked the significant finding of bipedalism in early hominids. It was thus concluded that bipedalism was earlier to develop, compared to enlarged brain in humans or mammals2.
Historical and Evolutionary Significance
The site is a significant milestone from the perspective of evolutionary history. It not will provide bipedalism, but also helped to categorize the species of Australopithecus afarensis, Paranthropus aethiopicus and Ardipithecus ramidus on the nature of their bipedal movements. The footprints found in the volcanic ashes were reconstructed by anthropologists T. White and G. Suwa belonging to University of California4. The reconstructions of footprints were made from a female hominin of the species Australopithecus afarensis4.
Further, these footprints were analyzed by R. Tuttle from the University of Chicago. It was revealed that Australopithecus afarensis had a gait pattern that resembled humans more compared to apes. His study was based on study of bipedal movements of humans and various nonhuman primates and other animals. He deeply investigated the gait patterns and foot structure of such animals and mammals. He took into account the stride length of the foot, the width of the footprints and the angle made by the foot on the ground. Such elaborative study provided another discovery that Australopithecus afarensis exhibited obligatory bipedalism. Moreover, sexual dimorphism was very well marked in these groups of individuals. It was revealed that the size of the brain of Australopithecus afarensis resembled the modern chimpanzees and gorillas than the modern human beings. The site was remarkably excavated and studied by these scientists for the features of bipedalism and the way bipedal movement developed till the modern times1.
The various features of bipedal movements that were elaborated included various anatomical and biomechanical variables. There was lateral transmission of force that took place from the base of the heel to the base of the lateral metatarsal. This indicated that although bipedalism existed such movements were not stable and the organism had to revert to occasional and obligatory bipedalism. This was supplemented by the finding that the foot had a medial and longitudinal arch that was oriented towards the lateral metatarsals. The big toe was much adducted outwards and the impression of the great toe was the deepest in the volcanic fossil remains. Hence, these evidences once again complemented the findings that bipedalism was very unstable and the force of movement and stability was based on the great toe3.
Information Retrieval
The information of the site is quite difficult to be revealed, because of the extensive layers that were formed over the history of time. Moreover, the layers were not demarcated much with respect to mineral deposits that might have provided an easy estimation of the evolutionary trends. The site was excavated through the technology potassium-argon dating of the various striations or rock beds that formed layers one over another, over the tides of time. The rock beds were classified according to various names and features and each had distinct characteristics that helped to provide the basis of hominin evolution. The layers or beds that were isolated include from the lowest. These are the lower Laetolil Beds (the deepest layer), Upper Laetolil Beds (the next layer after lower Laetolil Beds). This was succeeded on the top by Lower Ndolanya Beds and Upper Ndolanya Beds. Then the subsequent beds were the Ogol Laval beds, Naibadad beds, Olpiro beds and finally the Ngaloba Beds. All these four layers congruently defined the significant information, which was very important from the perspective of evolutionary history. The Upper Laetolil Beds produced the evidence of the primate footprints that embarked the bipedal evolution in primates. The Upper Laetolil Beds were formed around 3.7 to 3.8 million years ago and they had a thickness of 130m. The lower Laetolil beds produced no convincing presence of primate ancestry or mammalian trace. The Lower Ndolanya beds and upper Ndolanya beds were separated by one-meter thick calcrete. The evolutionary history of Ogol Lavas could not be ascribed appropriately however it would be somewhat around 2.4 million years ago. No mammalian ancestry was recovered from the Naibadad beds. However, the extensive study of mineral content of this layer provided evidence of Acheulean traits and fauna in the Olpiro beds. The Ngaloba beds were recent and traced back some 120000 to 150000 years ago3.
Detailed Studies
The major studies centered on the hominid footprints that were discovered by Mary Leakey. These footprints were identified from an 80 feet hominin fossil that was preserved in the volcanic ashes5. The volcano was supposed to be from nearby site that was 20 km away from the site of finding of the fossil. Sadiman volcano is approximated to be the likely volcano that erupted during those times. However, a current study done by Zaitsevet et al (2011)4, revealed that the volcanic rashes were not the agents of preserving the foot prints and it rained water that cemented the ash layer on to the fossil bed. The foot prints were not isolated from each other and there were other footprints in the vicinity which helped us to assume that such primates socialized as a nuclear family. The site also revealed various types of fauna. These fossils were of hyenas, antelopes, birds, buffaloes and elephants3.
Appraisal of the Excavated Site
The site is quite popular, on the basis of its evolutionary significance. Moreover, there are adequate popular and scholarly sources that designated the authenticity of the excavations and the conclusive findings. The journal resources published the data based on human anatomical and anthropological features that helped us to form evidence based literature on the bipedal movements. The literature and the resources are trustworthy and have impact rating amongst the scientific and archeological communities across the globe.
Summary and Conclusion
The hominid footprints provided the first conclusive evidence regarding the presence of bipedal mammals in the Pliocene era that traced back to 3.7 million years ago. The three hominids species that were isolated was Australopithecus afarensis, Paranthropus aethiopicus and Ardipithecus ramidus. The elaborative study was done on Australopithecus afarensis. Earlier in the history of evolution, it was predicted that enlarged brains were earlier to develop before bipedalism in primates. Excavation at Laetoli proved the earlier speculations wrong, and it was concluded that bipedalism was earlier to develop compared to enlarge brain in humans or primates. Australopithecus afarensis had a gait pattern that resembled humans more compared to apes.
Australopithecus afarensis resembled the modern chimpanzees and gorillas than the modern human beings, and they exhibited obligatory bipedalism. The nature of bipedalism indicated that lateral transmission of force took place from the base of the heel to the base of the lateral metatarsal. Moreover, the foot had a medial and longitudinal arch (like the human beings) which was oriented towards the lateral metatarsals. The big toe was much adducted and flanked. Such findings indicated that the force of movement and stability was based on the great toe. Apart from hominids certain faunal population was also retrieved from the fossils. These included hyenas, antelopes, birds, buffaloes and elephants. Various layers were identified from the site through potassium-argon dating. The Upper Laetolil Beds produced the evidence of the primate footprints. The Upper Laetolil Beds were formed around 3.7 to 3.8 million years ago and they had a thickness of 130m. The lower Laetolil Beds produced no convincing presence of primate ancestry or mammalian trace. However, the Olpiro beds produced evidence of faunal traits.
The site is important from the perspective of evolutionary history. However, apart from bipedalism the social behavior of such primates could have been explored in details. This could be based on various observations like finding the density of footprints near and away from the volcano. Such findings could help to identify their cognitive capacity of responding to danger.
Bibliography
Tuttle, R.H.. Footprint Clues in Hominid Evolution and Forensics: Lessons and Limitations. Ichnos. 15.3 (2008): 158–165
White, T.D. & Suwa, G.Hominid footprints at Laetoli: Facts and Interpretations. American Journal of Physical Anthropology. 72.4 (1987):485–514
Ditchfield, P. & Harrison, T. Sedimentology, Lithostratigraphy and Depositional History of the Laetoli Area. In T. Harrison (Ed.), Paleontology and Geology of Laetoli: Human Evolution in Context: Geology, Geochronology, Paleoecology and Paleoenvironment, Vertebrate Paelobiology and Paleoanthropology. Dordrecht, Netherlands: Springer, 1(2011): 47–76
Zaitsev, AN, Wenzel, T, Spratt, J, Williams, TC, Strekopytov, S, Sharygin, VV, Petrov, SV, Golovina, TA, Zaitseva, EO & Markl, G. (2011). Was Sadiman volcano a source for the Laetoli Footprint Tuff? Journal of Human Evolution 61.1(2011): 121–124
Leakey, M.D. (1981). Discoveries at Laetoli in Northern Tanzania. Proceedings of the Geologists’ Association. 92.2 (1981):81–86

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