Significations et usages de Olduvai_Gorge

Olduvai Gorge
Olduvai Gorge
Long-axis length	48 kilometres (30 mi)
Geography
Coordinates	2°59′37″S 35°21′04″E / 2.993613°S 35.35115°E / -2.993613; 35.35115Coordinates: 2°59′37″S 35°21′04″E / 2.993613°S 35.35115°E / -2.993613; 35.35115

Olduvai Gorge, the archaeological site also known as "The Cradle of Mankind", is a steep-sided ravine in the Great Rift Valley that stretches through eastern Africa. It is in the eastern Serengeti Plains in northern Tanzania and is about 48 km (30 mi) long. It is located 45 km from the Laetoli archaeological site. The name is a misspelling of Oldupai Gorge, which was adopted as the official name in 2005. Oldupai is the Maasai word for the wild sisal plant Sansevieria ehrenbergii, which grows in the gorge.^[1]

Olduvai Gorge is one of the most important prehistoric sites in the world and has been instrumental in furthering the understanding of early human evolution. This site was occupied by homo habilis approximately 1.9 million years ago, Paranthropus boisei 1.8 million years ago, and Homo erectus 1.2 million years ago. Homo sapiens are dated to have occupied the site 17,000 years ago.

This site is also significant in showing increased developmental and social complexities in hominins. Evidence of this is shown in the production and use of stone tools, which indicates the increase in cognitive capacities. There is also evidence indicating the practices of both scavenging and hunting, which is highlighted by the evidence of gnaw marks predating cut marks, and comparisons on percentages of meat versus plant in the early hominid diet. Furthermore, the collection of tools and animal remains in a central area is evidence of increases in social interaction and communal activity.

  History

  Research

  Olduvai Gorge from space

  Topography of Olduvai Gorge

  Close-up of monolith

Researchers dated Olduvai Gorge using radiometric dating of the embedded artifacts, mostly through potassium-argon dating and argon–argon dating. A German entomologist named Wilhelm Kattwinkel discovered Olduvai Gorge in 1911, where he noticed many fossil bones of an extinct three-toed horse. Kattwinkel's discovery inspired Professor Hans Reck to lead a team to Olduvai Gorge in 1913. There, he found a hominid skeleton, but unfortunately the start of World War I halted his research.

In 1931, Louis Leakey found Olduvai fossils in Berlin and thought Olduvai Gorge held information on human origins, and thus began excavating there. Louis and Mary Leakey are the archaeologists responsible for most of the excavations and discoveries of the hominid fossils in Olduvai Gorge. Their finds at Olduvai Gorge, when added to the prior work of Raymond Dart and Robert Broom, convinced most paleoanthropologists that humans originally evolved in Africa. It was at the FLK (Frida Leakey Korongo site named after Louis' first wife) in 1959 that Mary found remains of the robust australopithecine Zinjanthropus boisei (now known as Paranthropus boisei). The specimen's age of 1.75 million years radically altered the accepted ideas about the time scale of human evolution. They also found and studied more than 2,000 stone tools and flakes at the site, which were classified as Oldowan tools, in addition to an abundance of faunal remains. Louis Leakey's son Jonathan found the first specimen of Homo habilis, a jaw fragment, at Olduvai in 1960.

In the late 1990s and early 2000s, Professor Fidelis Masao of the Open University of Tanzania led his team to excavate at Olduvai Gorge. These researchers focused on stone tools and animal bones bearing butchery marks in order to reveal the activities of long-ago human ancestors. Masao also studied the rock art paintings found in the region.

  Panoramic view

The geology of Olduvai Gorge and the surrounding region was studied in detail by Richard L. Hay, who worked at the site between 1961 and 2002. His finding revealed that millions of years ago the site was a large lake, with shores covered with deposits of volcanic ash. Around 500,000 years ago seismic activity diverted a nearby stream which began to cut down into the sediments, revealing seven main layers in the walls of the gorge.

  Occupation

Homo habilis is thought to have occupied the site from 1.9 to 1.6 million years ago. Paranthropus boisei was found to occupy the site from approximately 1.8 million years ago until 1.2 million years ago. Homo erectus remains were found and dated at the site from 1.2 million years ago until 700,000 years ago. It wasn't until 17,000 years ago that Homo sapiens came to occupy the gorge.

  Significance

  Toolmaking

  Oldowan Stone Chopper

  The oldest object within the walls of the British Museum. Dated to approximately 1.8 million year of age

In the 1930s, as Mary and Louis Leakey searched for earliest stone tools in east Africa, many people were skeptical that Africa was the place that humans evolved. Yet when the Leakeys found tools in Olduvai Gorge, evidence turned in their favor. These Oldowan tools had sharp and shaped edges. Lithic flakes were taken off in the intentional shaping of the tools' points.

The Leakeys recorded the particular locations in which the tools were found and compared these positions to locations where the raw materials originated. When it was found that these tools were transported up to 9 miles from the materials' place of origin, this suggested cognitive capacities to plan and think, and also to carry materials. While these Oldowan tools were found in the same stratum as the Australopithecus specimen, the multitude of other hominin fossils found dating back to two million years ago complicated the discussion of which species was in fact the toolmaker.

The first species found by the Leakeys, Zinjanthropus boisei or Australopithecus boisei (renamed and still debated as Paranthropus boisei), featured a sagittal crest and large molars. These attributes suggested that the species engaged in heavy chewing, indicating a tough diet consisting of tubers, nuts, and seeds.

Conversely, the Leakeys' 1960s find held many different characteristics. Firstly, its lack of saggital crest and much more rounded braincase suggested it was not an Australopithecine. This newer fossil's skull also suggested a much bigger brain capacity than the previously found Australopithecus boisei. These stark differences indicated that this fossil must have belonged to a different species, eventually dubbed Homo habilis. Its cognitive capacity and decreased teeth size identified Homo as the toolmaker.

  Hunters or Scavengers?

Though substantial evidence of hunting and scavenging has been discovered at the site, it is believed by archaeologists that the hominins that inhabited the area between 1.9 and 1.7 million years ago spent the majority of their time gathering wild plant foods such as berries, tubers and roots. Though there is substantial archeological evidence for meat in ancient hominin diet, early hominins were most likely not relying heavily on meat for nutrition. This speculation about the amount of meat in their diet comes from comparative studies with a close relative of early humans: the chimpanzee. The chimpanzee's diet only consists of about 5% of meat. Furthermore, modern hunter-gatherers' diet also does not consist of a large amount of meat. As a result, the majority of the calories in their diets both come from plant sources. By the middle-range theory or bridging arguments, it can be assumed that early hominins also had similar diet proportions. These bridging arguments are used by archaeologists to explain past behaviors and includes an underlying assumption of uniformitarianism.

  Paranthropus in a Savannah setting

Much of the information we have about early hominins comes from tools and piles of garbage from the sites like FLK-Zinjanthropus (also known as FLK-Zinj and where the "Zinj" skull was discovered) in Olduvai Gorge. Early hominins picked special types of rocks that would break in a predictable manner when "worked" to create tools and carried these rocks from deposits several miles away. By fitting rock fragments back together like a puzzle, archaeologists, like Fiona Marshall states in her article "Life in Olduvai Gorge," have been able to determine that early hominins "knew the right angle to hit the cobble, or core, in order to successfully produce sharp-edged flakes. Such flakes were used to cut meat off animal carcasses. Shaped cobbles (called choppers) were probably also used to extract the marrow from inside the bones, or to chop up plant foods."

Bird, fish, amphibian, and large mammal bone fragments were found at the FLK-Zinj site, some of which had marks on them. These could have been made by hominins breaking open the bones for marrow, using tools to strip the meat, or from carnivores who had gnawed on the bones. Since there are both kinds of marks on them some archaeologists think that the hominins at FLK-Zinj scavenged the meat or marrow that was left over from carnivore kills. Others believe that hominins hunted these animals and the carnivores chewed on the bones that were leftover. This is a controversial point that is still debated today, but archaeologist Pat Shipman's did a study proved that evidence of scavenging was most common, meaning that the majority of carnivore teeth marks came before the cut marks. Other findings during Pat Shipman's research at FLK-Zinj revealed that many of the wildebeest bones found at the site were of strong, male wildebeest and this indicates that humans were hunting these animals, as carnivores like hyenas hunt only the weak, very young and elderly of a herd. This would indicate that humans were not only scavenging but hunting as well. The issue of hunting versus gathering at Olduvai Gorge is clearly a controversial one. Further evidence found at nearby sites helped to clarify some of this debate.

  Cooperation

At the site of FLK Zinj, the fact that tools and remains of animals were all brought to one central place may be indicative of early hominin cooperation. This 'communal' location may have been a camp or a larger social living group. This characteristic sets humans apart from close relatives like chimpanzees as chimps are more reluctant to share than humans are. The important traits of cooperation and sharing became more important around two million years ago.

  See also

• Geography of Tanzania
• List of fossil sites
• Olduvai imperative
• Olduvai theory

  References

• 2004 - 2011. Olduvai Gorge – The Cradle of Mankind. http://www.tanzania- adventure.com/olduvai.htm, accessed December 2, 2011.
• 2005. Chapter Outline. http://highered.mcgrawhill.com/sites/007299634x/student_view0/chapter2/chapter_outline.html, accessed December 2, 2011.
• Cole, Sonia (1975) Leakey's Luck. Harcourt Brace Jovanvich, New York.
• Colin Renfrew and Paul Bahn Archaeology Essentials 2007 Archaeology Essentials, 2nd Edition. Thames & Hudson Ltd, London.
• Deocampo, Daniel M. (2004) "Authigenic clays in East Africa: Regional trends and paleolimnology at the Plio-Pleistocene boundary, Olduvai Gorge, Tanzania." Journal of Paleolimnology, vol. 31, p. 1-9.
• Deocampo, Daniel M., Blumenschine, R.J., and Ashley, G.M. (2002). "Freshwater wetland diagenesis and traces of early hominids in the lowermost Bed II (~1.8 myr) playa lake-margin at Olduvai Gorge, Tanzania." Quaternary Research, vol. 57, p. 271-281.
• Hay, Richard L. (1976) "Geology of the Olduvai Gorge." University of California Press, 203 pp.
• E. Gengo, Michael. "Evidence of Human Evolution, Interpreting." Encyclopedia of Time: Science, Philosophy, Theology, & Culture. 2009. SAGE Publications. 5 Dec. 2011. <http://www.sage-ereference.com.proxy.lib.umich.edu/view/time/n200.xml>
• Hominin Migrations Out of Africa. Lisa Young. Introduction to Prehistoric Archaeology. University of Michigan. October 2, 2011.
• Joanne Christine Tactikos (2006) A landscape perspective on the Oldowan from Olduvai Gorge, Tanzania. ISBN 0-542-15698-9.
• Louis and Mary Leakey: Biography. http://www.macroevolution.net/mary-leakey-2.html#.Ttw4uHNZjZA, accessed December 4, 2011.
• Leakey, L.S.B. (1974) By the evidence: Memoirs 1932-1951. Harcourt Brace Jovanavich, New York, ISBN 0-15-149454-1.
• Leakey, M.D. (1971) Olduvai Gorge: Excavations in beds I & II 1960–1963. Cambridge University Press, Cambridge.
• Leakey, M.D. (1984) Disclosing the past. Doubleday & Co., New York, ISBN 0-385-18961-3.
• Marshall, Fiona. "Life in OLDUVAI GORGE." Calliope Sept. 1999: 16. General OneFile. Web. 4 Dec. 2011.
• The First Stone Tool Makers. Lisa Young. Introduction to Prehistoric Archaeology. University of Michigan. September 25, 2011.

  External links

• Oldupai Gorge – History & Information
• Olduvai Gorge - Getting There, Location & Information
• Natural History museum in Arusha
• Information about Northern Tanzania - Oldupai