|Long-axis length||48 kilometres (30 mi)|
Olduvai Gorge or Oldupai Gorge in Tanzania is one of the most important paleoanthropological 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 is dated to have occupied the site 17,000 years ago. Olduvai Gorge is a steep-sided ravine in the Great Rift Valley that stretches through eastern Africa. It is in the eastern Serengeti Plains in Arusha Region, Tanzania and is about 48 km (30 mi) long. It is located 45 km (28 mi) from the Laetoli archaeological site.
This site is 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. Evidence also indicates the practices of both scavenging and hunting, which are 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.
Researchers dated Olduvai Gorge using radiometric dating of the embedded artifacts, mostly through potassium-argon dating and argon–argon dating. German neurologist Wilhelm Kattwinkel traveled to 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, when added to the prior work of Raymond Dart and Robert Broom, convinced most paleoanthropologists that humans originally evolved in Africa. At the Frida Leakey Korongo (FLK) site (named after Louis' first wife) in 1959, 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 to reveal the activities of long-ago human ancestors. Masao also studied the rock art paintings found in the region.
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, 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.
The name Olduvai 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.
Homo habilis is thought to have occupied the site from 1.9 to 1.2 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. Homo sapiens came to occupy the gorge 17,000 years ago.
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 where 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 these tools were found to have been 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 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 sagittal 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 this fossil must have belonged to a different species, eventually named Homo habilis. Its cognitive capacity and decreased teeth size identified Homo as the toolmaker.
The lowest (oldest) tools located were Oldowan which consisted of pebbles chipped on one edge. Above this were true hand-axe, Chellean, and Acheulean industries. Higher still are located Lavalloisean and finally the Stillbay implements. Mary Leakey herself developed Oldowan A,B, and C linking them to Modes one assemblages. Today her work remains a foundation for assessing local, regional, and continent-wide changes in stone tool-making during the early Pleistocene. It also helps to consider which species of hominins were responsible for the changes in stone tool over time. 
The oldest object in the British Museum
Hunters or scavengers?
Though substantial evidence of hunting and scavenging has been discovered at the site, it is believed by archaeologists[who?] 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 substantial archaeological evidence for meat in ancient hominin diets exists, early hominins were most likely not relying heavily on meat for nutrition. This speculation about the amount of meat in their diets comes from comparative studies with a close relative of early humans: the chimpanzee. The chimpanzee's diet only consists of about 5% meat. Furthermore, modern hunter-gatherers' diets also do not consist of a large amount of meat. As a result, the majority of the calories in both their diets came 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 include an underlying assumption of uniformitarianism. Much of the information about early hominins comes from tools and piles of garbage from the sites such as the 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, such as Fiona Marshall states in her article "Life in Olduvai Gorge", have been able to determine the 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 which had gnawed on the bones. Since both kinds of marks are present on them, some archaeologists, namely Lewis Binford, think the hominins at FLK-Zinj scavenged the meat or marrow left over from carnivore kills. Others like Henry Bunn believe hominins hunted these animals and the carnivores chewed on the bones left over. This controversial point is still debated today, but archaeologist Pat Shipman's study proved the evidence of scavenging was most common, meaning the majority of carnivore teeth marks came before the cut marks. Other findings during Shipman's research at FLK-Zinj revealed many of the wildebeest bones found at the site were of an adult, male wildebeest, and this indicates humans were hunting these animals, as carnivores, such as hyenas, tend to hunt the weak, young and elderly. This would indicate 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.
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