Sandbox:ARCL 140 Final Project
Evolution of Human Diet
Contributors & Roles
Site 1:
Site 2: Amy de Boer
Site 3: Jessica Yuen
Site 4:
Map
Introduction
Site 1:
Author:
Location:
Age:
Context
History
Relevance
Site 2: Nariokotome III
Author: Amy de Boer
Location: West Lake Turkana, Kenya (4.15861, 35.90854)
Age: 1.51-1.56 Ma
Context
The KNM-WT 15000 or “Turkana Boy” fossil is the most complete Homo erectus fossil ever discovered. It was found by Kamoya Kimeu in August of 1984 near Lake Turkana in Kenya. While most fossils are found on the east side of the lake at the Koobi Fora formation, this fossil was discovered on the west, 5 km inland from Lake Turkana by the Nariokotome river. This site was later named Nariokotome III (NK3). The age of this site was determined via isotopic dating, mainly by the K-Ar method on the volcanic material in the tuffaceous beds. The age of four tufts surrounding the fossil was taken and used to determine that the age of this fossil is between 1.51-1.56 Ma (Walker & Leakey, 1993).
Today, Nariokotome is a large stream that flows into Lake Turkana and always has water, even in the dry seasons. It is home to small troops of velvet monkeys who occupy the middle stretches. At the time of the death of the “Turkana Boy”, the area was most likely a floodplain marsh, with narrow belts of trees bordering the site. Small juvenile fish fossils were discovered indicating a shallow, heavily vegetated habitat of short duration (Walker & Leakey, 1993).
History
NK3 was established after Kamoya Kimeu discovered a piece of hominid cranial vault on the slopes of the Nariokotome river in August 1984. Sieving operations began a week later and most of the cranium was discovered, followed by more parts of the juvenile skeleton. The excavations were halted in September due to lack of funds. They resumed the next year after the find was published and then the missing teeth were recovered. The third and fourth years produced a few more bones, but nothing was discovered the fifth year. Excavation was stopped in 1988. Over the course of the excavation, 425 square metres were exposed, higher than average compared to other digs (Walter & Leakey, 1993).
Relevance
The discovery of the “Turkana Boy” fossil was crucial in enhancing our understanding of early human morphology. It is the most complete Homo erectus fossil found. However his age at time of death differs from the dental and skeletal records. Determining age, height, and weight was difficult because of our limited understanding of Homo erectus growth patterns. It was eventually estimated that age-at-death was around 8 years according to dental structure analysis while skeletal records indicate an age-at-death around 15 years (Ruff & Burgess, 2015).
The dental remains of this fossil and other Homo erectus fossils are important in understanding the diet and consequent lifestyles of this species. Home erectus had smaller molars, cheek teeth, and incisors. Processed foods require less chewing, so larger incisors and molars are no longer necessary. The cheek teeth in Homo erectus have values approaching those of modern humans. This could be a way to slow down the digestion process or reduce dental crowding in a shorter jaw. As well, there is a broader range of microwear texture complexity which indicates a consumption of a wider variety of foods and tougher foods than the hominins that came before Homo erectus (Unger, 2011).
Furthermore, it is hypothesized that the much larger brains of Homo erectus required a more nutritious diet to support the energetic costs of this organ. It is suggested that this energy-rich diet consisted of animal meat and marrow, honey, and underground tubers (Antón, 2003). While the evidence for the use of fire to cook their food comes after Homo erectus, the presence of tools is a good indicator that meat was an important, but not exclusive shift in the evolving hominin diet. As well, the narrow bi-iliac breadth of the “Turkana Boy” pelvis reflects a significant decrease in gut size due to the “Expensive Tissue Hypothesis” (Aiello & Wheeler, 1995).
Site 3: Olduvai Gorge
Author: Jessica Yuen
Location: Olduvai Gorge, Tanzania (-2.98957, 35.355391)
Age: 1.75-1.85 Mya
Context
The Olduvai Hominid 62 (OH62) is one of the three Homo habilis fossils discovered from east of palaeolake Olduvai on July 21 1986. OH62 was found on the uppermost Bed Ⅰ that dates to approximately 1.8 million years ago (Mya) but OH62 is inferred to be around 1.75 to 1.85 Mya. Bed Ⅰ is the result of lava flows, volcanic ash deposits, and detritus sediments through weathering and erosion. The upper part of the bed, Tuff IF, is a series of wet and dry climate shifts, and the lower part of the bed forms the current-day valley floor (Johansen et al., 1987).
History
Olduvai Gorge has been an important paleoanthropological site where new hominid species were discovered from the 1950s to 1970s. In August of 1995, a set of hominin maxilla with complete dentitions was discovered and excavated by Agostino Venance and A. Cushing. The fossils were grouped into OH65 (Clarke, 2012). The OH65 was discovered through picking at deposits near Trench 57 near Naisiusiu. During excavation, the tool used to pick the maxilla was accidentally shattered. The maxilla shattered into three parts: right posterior maxilla, left posterior maxilla, and the anterior maxilla. The broken pieces were super glued back together carefully to ensure that the specimen is preserved. Despite the shatter, the maxilla remains in fairly good shape except for its thinned-wall and small cracks near the surface of the nasoalveolar clivus (Clarke, 2012). Additionally, there were over 18000 fragments of bones and teeth that were excavated (Johansen et al., 1987). Tooth enamel is one of the most reliable techniques in measuring water excretion, diet, and water intake of an animal because the enamel is resistant against chemicalization (Van der Merew et al. 2008).
Relevance
The bones that were found at the site included maxillary, calvarial, mandibular, radial, humeral fragments, femoral and tibial fragments. The OH65 showed features belonging to Homo habilis. The features that distinguish Homo habilis (OH65) from Australopithecus were the wide and short U-shaped palate, long and straight canines, broad and flat infranasal surface of the maxilla, and the large roots of the cheek teeth (Clarke, 2012).
The incisor-molar index indicated that Homo habilis were in between chimpanzees with a large incisor-molar index and orangutans with an intermediate incisor-molar index (Ungar, 2011). This index indicated that H. habilis ate grass, plants, and meat as well (Ungar, 2011). Another supporting evidence is the microwear pit-scratch ratio. This ratio showed association with a diet of hard and tough foods (Ungar, 2011). Although tooth size in H. habilis does not seem to decrease immensely, the occlusal area is shown to be reduced. The larger the cheek tooth area, the more surface area there is to process large amounts of food. The slightly smaller incisors and molar teeth implies that there is less selective pressure for large teeth with the increasing usage of stone tools. Stone tools can help increase the surface area of the food allowing for less mechanical breakdown required in the mouth (Ungar, 2011).
There are many other skeletal models including OH7 and OH62 that show different parts of the anatomy that has evolved. The differences in each model demonstrates that all the adaptations do not occur at once, but instead, selection for a certain feature happens one at a time (Ungar, 2011).
Site 4:
Author:
Location:
Age: