Course:ARCL140 Summer2020/TermProject Group 21
Contributors & Roles
Alex Dines: Introduction, site 4 and editing
Maddy Nowell: Map, site 1, conclusion and editing
Chloe Coleman: Site 2, conclusion and editing
Crisangi Kumeran: Site 3 and editing
Map
Laetoli, Tanzania: 3.22491ºS, 35.19175ºE
Lucy/Dinknesh, Ethiopia: 10°49'59.6"N 41°18'30.7"E
Turkana Boy, Kenya: 4.08º N, 35.54º E
Sangiran Dome, Java: 7.27° S, 110.50° E
Introduction
Among the great apes, habitual bipedalism is a unique trait to humans, “perhaps the most influential structural and behavioural adaptation in early hominin development” (Watson et al. 2008), but its origins and implications are often subject to debate. Some anthropologists believe that bipedalism emerged as a result of the dramatically changing landscape (Winder et al. 2013), climate (Winder et al. 2013), or evolving morphology (Thorpe et al. 2014), and there is also debate as to the process in which early hominids stopped being primarily arboreal (Thorpe et al. 2014). Bipedalism can be observed in very different ways such as dating certain bones, scanning bones for microscopic differences or similarities, and drawing conclusions based on the ecology of the areas fossils are found, as explored in the four sites and fossils selected for this topic. All of these factors contribute to how bipedalism adapted from primates who do not use habitual bipedalism to humans whose primary form of locomotion is walking and running upright (Demes and O’Neil 2012). By tracking the evolution of bipedalism, anthropologists can gain insight into how our species and those closely related to us traveled, interacted with one another, their growth development, and more. Bipedalism can be seen amongst various hominid species (Ryan et al. 2018) and the purpose of providing key examples of each major step in the evolution of bipedalism allows anthropologists to observe how advantageous traits are selected for and evolve. The sites/fossils chosen are all important in telling the story of the evolution of bipedalism in hominids and demonstrate how bipedalism became an advantageous trait for hominids. The oldest example is that of Laetoli in Tanzania, then Lucy in Ethiopia, followed by the Turkana Boy in Kenya, and finally the Sangiran Dome site in Indonesia. These sites/fossils demonstrate the gradual expansion of hominids from their first settlements in Africa and over time into Asia.
Site 1: Laetoli, Tanzania
Author: Maddy Nowell
Location: The site can be found within the Ngorongoro Conservation Area at the southern edge of the Serengeti Plains in northern Tanzania (Masao et al. 2016). It is roughly 36 kilometers south of the Olduvai Gorge (Musiba et al. 2008). Its exact coordinates are 3.22491ºS, 35.19175ºE
Age: The site was discovered in 1978 and can be dated back to roughly 3.7 million years BP (Lockley, Roberts and Kim 2008).
Context: The Laetoli site can be found in northern Tanzania, more specifically in the Ngorongoro Conservation Area (Masao et al. 2016). It was discovered in 1978 by Mary Leakey and her team and dates back to roughly 3.7 million years ago (Lockley, Roberts and Kim 2008). Through their study, Denise F. Sue and Terry Harrison were able to conclude that Laetoli was likely a combination of woodland, shrubland, and grassland with significantly more vegetation than there is now (Su and Harrison 2008). The site also likely included ponds and ephemeral streams (Su and Harrison 2008). It did not contain any major rivers or lakes and was found of aeolian volcanic tuffs (Musiba et al. 2008). Currently, the site consists of a drier shrubland and grassland ecosystem (Su and Harrison 2008). Since its discovery, scientists have been able to conclude that the footprints found at the site were likely left by the Australopithecus afarensis species and that this species was likely uncommon in the region at that time (Su and Harrison 2008). It is believed that their low population in this location was likely attributed to predation in the surrounding areas (Su and Harrison 2008). Other animals that were likely present when the tracks were made include giraffes, rhinoceros, and baboons (Musiba et al. 2008).
History: The Laetoli site was discovered in 1978 by Mary Leakey and her team (Musiba et al. 2008). In the 1930s before the site had been discovered, the surrounding area had already begun to gain paleontological significance (Masao et al. 2016). This is because within the Ngorongoro Conservation Area lies sites such as the Olduvai Gorge and Lake Ndutu (Masao et al. 2016). These sites contain many volcano-sedimentary deposits that date back to the Pliocene and the Pleistocene (Masao et al. 2016). However, Laetoli specifically is credited with the evidence of the earliest known hominid bipedalism (Masao et al. 2016). The footprints that were found at the site are widely believed to belong to the Australopithecus afarensis species (Lockley, Roberts and Kim 2008). Although this site is most well known for its evidence of bipedalism, it also contains prints left by animals which are now extinct such as the Simatherium Kohllarseni (Musiba et al. 2008).
Relevance: The footprints found at this site are the oldest known footprints left by hominids (Lockley, Roberts and Kim 2008). They are the only undisputed evidence of bipedal locomotion from hominids from the Pliocene (Musiba et al. 2008). Although it is believed that the footprints were left by Australopithecus afarensis, the same species as the Lucy fossil, some of the tracks that were found appear to belong to a larger sized species (Lockley, Roberts and Kim 2008). When looking at the site, it can be assumed that the tracks were left by a juvenile and two adult individuals based of the size of the footprints (Lockley, Roberts and Kim 2008).When comparing Lucy’s foot size to those of the prints left at Laetoli, her foot was too small to fit into the larger tracks and too large to fit into the smaller ones (Lockley, Roberts and Kim 2008). This suggests that there is a possibility that the prints were left by a different, possibly more evolved species of hominid. However, the footprints are not the only discovery found at this site. Leakey’s team was also able to discover over twenty fragments of cranial and postcranial hominid fossil remains (Musiba et al. 2008). Interestingly enough, these remains not only belonged to Australopithecus afarensis, but also to other hominins ranging up to the anatomically modern humans (Musiba et al. 2008). This means that the site not only shows the earliest known evidence of habitual bipedalism among the homosapien lineage, but also cranial evidence of human evolution in the site’s surrounding area.
Site 2: Lucy/Dinknesh, Ethiopia
Author: Chloe Coleman
Location: AL 228-1 (commonly known as Lucy or Dinkinesh) was found in an isolated spot in the Awash Valley of the Afar Triangle in Ethiopia, Africa. The exact coordinates are 10°49'59.6"N 41°18'30.7"E
Age: Lucy was discovered in 1974 and has been dated to just under 3.18 million years BP.
Context: In 1973 Donald Johanson, Yives Coppens, and Maurcie Taieb formed the International Afar Research Expedition (IARE) in order to begin intensive explorations of the richly fossiliferous pliocene fluvio-lacustrine deposits exposed along the Awash river in the Afar Triangle (Kimbel et al. 2009). Hadar lies along the northern part of Africa’s Eastern Great Rift Valley, approximately 300 km north east of Addis Ababa, Ethiopia’s Capital. The Hadar Formation was first recognised for the fossiliferous rocks at Hadar by Maurcie Taieb et al (Kimble et al. 2009). The Hadar Formation consists primarily of fluvio-lacustrine related mudstones, siltstones, fine-grained sandstones and volcanic tuffs (Taieb et al. 1972). Hadar, as described by Johanson (1981) in his book Lucy: The Beginnings of Humankind, was an ancient lake bed that has since dried and is now a wasteland of bare rock, gravel and sand.
History: Due to the exposed, richly fossiliferous Pliocene fluvio-lacustrine deposits along the seasonally dry Awash river in Kenya, a variety of researchers with the IARE surveyed the area throughout the years and discovered many hominid fossils (Kimble et al. 2009). Some of the fossils include AL 128-1 and AL 129-1a,b,c (Kimble et al. 2009). Though incredibly important and exciting discoveries, they were upstaged by the discovery of the skeletal remains AL 288-1, also known as “Lucy”. The Lucy site was discovered in Hadar, Ethiopia, by Donald Johanson and Tom Grey on November 24, 1974. The two researchers ventured down the previously surveyed gully where Johanson spotted a fossil on their way out. A fragmented piece of bone, later identified as a section of a hominid arm, was spotted on the side of the slope (Johanson et al. 1981). Nearby the researchers found fragments of a small skull, femur, ribs, pelvis, and lower jaw (Kimble et al. 2009). After the discovery of AL 288-1, the researchers celebrated back at the camp and listened to “Lucy in the Sky with Diamonds” by the Beatles, from there on she was named “Lucy” (Johanson et al. 1981). In addition to Lucy, she has been given the name Dinkinesh which means “you are marvelous” in the local Amharic language. For the next three weeks careful excavation and collection continued in that location. Based on the hundreds of excellently preserved bone fragments found, with no duplication, researchers determined that all the fragments belonged to a singular individual (Gruss et al. 2017). The fragments, once reconstructed, made up 40% of a complete hominid skeleton. Since then with the permission of the Ethionian government Lucy has been transported by Johanson to the Cleveland Museum of Natural History. In North America there have been many tests conducted on the specimen since it’s transportation. This includes an initial attempt to find the age of the fossil by using potassium-argon radiometric dating. Years later, the more precise technology of argon-argon dating was used to find the more accurate date of just under 3.18 million years BP (Kimble et al. 2009).
Relevance: At the site, 40% of the remains of a singular female Australopithecus afarensis were found. These remains were discovered while surveyingan an exposed gully by Donald Johanson and Tom Grey. As mentioned by Johanson (1981), on the first day they discovered a piece of a hominid arm, the back of a small skull, part of a femur, a couple vertebrae, part of a pelvis, and a couple pieces of a jaw, later to be confirmed as all belonging to one individual. Over the next few weeks they revealed several hundred bone fragments representing the one individual (Johanson et al. 1981). In total they found 40% of a singular hominid skeleton. Lucy’s entire skeletal structure has been altered to accommodate regular bipedal locomotion (Johanson et al. 1981). Some of these alterations are evident in the unique variety angles and deterioration found on her femur, condyle, pelvis, talus, vertebrae, and patella. The importance of this find is astronomical as at the time the recovered specimen was the oldest, most complete, and best-preserved skeleton of any erect-walking human ancestor that had ever been found (Johanson et al. 1981).
Site 3: Turkana Boy, Kenya
Author: Crisangi Kumeran
Location: The site can be found at Nariokotome, west of Lake Turkana in Kenya (Brown et al. 1985). The exact coordinates are 4.08’ N, 35.54’ E.
Age: A large number of hominid fossils have been found around the Turkana lake. The most famous discovery: Turkana Boy, a Homo ergaster (alternately referred to as African Homo erectus) was found in 1984 and dates back 1.6 million years ago (Brown et al. 1985).
Context: The site is located on the western side of Turkana Lake in Kenya. It was discovered by Kamoya Kimeu in 1984. During the palaeontological exploration of Lake Turkana, Kamoya Kimeu found a small fragment of hominid frontal bone exposed on the surface of the ground near the south banks of Nariokotome river (Brown et al. 1985). This led to the discovery of the Turkana Boy (also known as Nariokotome Boy). The turf above the hominid was identified as a component ash of the Shungura Formation and through this they were able to determine that the hominid was 1.6 million years old (Brown et al. 1985). The strata at and around the site consisted of several layers of pale yellowish-brown sandstones and siltstones (Brown et al. 1985). Mammalian fossils were a rare find at the location. It usually consisted of vertebrate fossils of small and large fish (Brown et al. 1985). Today the Turkana Lake is known to be the world's largest desert as well as alkaline lake and is home to a variety of species.
History: During the paleontological exploration of the Turkana Lake region in 1984, one of the researchers, Kamoya Kimeu, happened to come across a small fragment of hominid frontal bone exposed on the surface of the ground. Following this initial discovery, screening and washing of surface float and pebble lag led to the recovery of most of the hominid calvaria (Brown et al. 1985). Further excavation of the area presented with more results such as several isolated teeth and much of the postcranial skeleton within the ~5x6m area of the initial find (Brown et al. 1985). Upon observation it was found that the skeleton was dispersed before final sedimentary burial. Many signs of bioturbation were found around the site, suggesting that many of the large bones had been trampled by larger animals (Brown et al. 1985). On rearranging the bones collected, the hominid seemed to be smaller than the average size of a Homo sapien (Schiess et al. 2013).
Relevance: The discovery of the Turkana Boy has led to further understanding of the morphology and proportions of the Homo erectus species (Brown et al. 1985). Initially, many felt that the small structure of the Turkana Boy was a result of dwarfism (Schiess et al. 2013). However, keeping in mind that over the years our species has increased in body proportions, it was concluded that the hominid could have been a result of a genetic potential left over (Brown et al. 1985). More research concluded that given the age of the Turkana Boy (12 years of age), his body proportions were similar to that of an adolescent Homo sapiens (Schiess et al. 2013). In terms of bipedalism, the long arm and leg bones indicated that the Homo erectus was capable of complete terrestrial bipedalism (Marshi et al. 2019).
Site 4: Sangiran Dome, Java
Author: Alex Dines
Location: The site of the Sangiran Dome or the Sangiran Early Man site is on the island of Java, Indonesia and is located in central Java east of the capital Jakarta (Bettis et al. 2009). Its exact coordinates are 7.27° S, 110.50° E.
Age: This site contains Homo Erectus fossils from the Early Pleistocene and varies from other sites in Indonesia as they are the earliest Homo Erectus fossils on the island (Kaifu et al. 2008). The timer range estimated for at least some of the fossils found is roughly between >1.5 million years ago to 0.9 million years ago (Puymerail et al. 2012).
Context: The Sangiran Dome on the island of Java, Indonesia is a very important site in terms of its collection of Homo Erectus fossils and what these fossils can tell anthropologists about the Early Pleistocene. Indonesia in general is the “earliest Asian sign of, and most distant point in [the] first human dispersal” (Bettis et al. 2009) and has been a point of interest in the field of anthropology because of its unique nature. The Sangiran Dome specifically “offers a stratigraphic into the Solo Basin” which is a key component of the area the fossils are found in. The geography in and surrounding the Sangiran Dome contains “the Solo Basin, part of a Pilo-Pleistocene intra-arc basin along the Southern margin margin of Sundaland” (Bettis et al. 2009) which has yielded many different Homo Erectus fossils as well as “other vertebrae fossils representing early Sundaland terrestrial faunas” (Bettis et al. 2009). The area in and around the Sangiran Dome is theorized to have been a part of the “wet tropical environments” unique to Java at the time of Homo Erectus as compared to the savannah landscape of Africa. The fossils themselves are commonly found in marshy and riverine deposits (Bettis et al. 2009) and also indicate the presence of volcanic activity due to the amount of black clay found at the site (Bettis et al. 2008). It is theorized that Homo Erectus “arrived in southern Sundaland during one or more early Pleistocene sea-level low stands…[and] most likely made their first crossing...between 1.8 to 1.74 Ma” (Bettis et al. 2009) based on fossil remains and research conducted regarding sea-levels (Bettis et al. 2009).
History: Java itself is home to many different hominin fossils including teeth (Zanolli 2013), crania (Kaifu et al. 2008), and lower limb bones such as femurs (Puymerail et al. 2012). The site at Sangiran was discovered in the nineteenth century (Bettis et al. 2009) by E. Dubois who discovered the first Homo Erectus fossils in the area (Zanolli 2013). Since this first discovery, the site has had “a long history of colonial, national, and international research” (Bettis et al. 2009) due to its extensive amount of information regarding both the lives of Homo Erectus as well as the environment they might have lived in (Bettis et al. 2009). Work has also been conducted since the 1980’s by French and Indonesian excavation teams who have excavated the area for “a better understanding of the geological and paleoenvironmental context” (Zanolli 2013), demonstrating the site’s unique nature of containing both clues to early hominids and their environment.
Relevance: The site of the Sangiran Dome has been the centre of many different hominin discoveries, specifically those belonging to Homo Erectus. In terms of relating to bipedalism, a femur belonging to a fossil named Kresna 11 is of particular interest as it offers a glimpse as to how Homo Erectus might have moved around and traveled as extensively as they did (Puymerail et al. 2012). The femur, a left femoral shaft, was recovered in 1992 and belongs to a Homo Erectus from the Early Pleistocene era. This shaft was studied extensively and found to be more closely related to Modern Humans rather than archaic Homo species such as Neanderthals, which indicates that these Homo Erectus had longer legs than other Homo species (Puymerail et al. 2012). Having longer legs would therefore enable Homo Erectus to travel more efficiently and given that they reached the Sangiran Dome site demonstrates how efficient bipedal locomotion was for them. As well, “the gluteal line (lateral) line is well marked and roughened laterally”(Puymerail et al. 2012) which can be an indication for “hav[ing] large lateral buttresses” (Puymerail et al. 2012) which could be connected to supporting a body standing on two feet instead of four.
Conclusion
When looking at the highly debated human origin, habitual bipedalism commonly plays a significant part. Many archaeologists and anthropologists hypothesize that the ever changing landscape, climate, and evolving morphology contributed to the emergence of bipedalism among hominids, with some debate on when they ceased to be arboreal. Ecology, differences in bone structure, and the dating of fossils have all contributed to the study of the evolution of bipedalism. Each of these factors have aided anthropologists’ ability to gain insight into how primate locomotion has evolved and how we interacted with each other. The sites previously discussed have aided in the tracking of bipedal evolution and how the gradual change in locomotion became an advantageous trait for hominids.
References
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