The Olduvai Gorge or Oldupai Gorge is a paleoanthropological site in northern Tanzania. Many sites exposed by the gorge have proven invaluable in furthering understanding of early human evolution. A steep-sided ravine in the Great Rift Valley that stretches across East Africa, it is about long, and is located in the eastern Serengeti Plains within the Ngorongoro Conservation Area in the Olbalbal ward located in Ngorongoro District of Arusha Region, about from Laetoli, another important archaeological locality of early human occupation. The British/Kenyan paleoanthropologist-archeologist team of Mary and Louis Leakey established excavation and research programs at Olduvai Gorge that achieved great advances in human knowledge. The site is registered as one of the National Historic Sites of Tanzania.
The gorge takes its name from the Maasai word oldupai which means "the place of the wild sisal" as the East African wild sisal (Dracaena hanningtonii) grows abundantly throughout the gorge area. Twenty-five kilometers downstream of Lake Ndutu and Lake Masek, the gorge is the result of up to erosion cutting into the sediments of a Pleistocene lake bed. A side gorge, originating from Lemagrut Mountain, joins the main gorge from the mouth. This side gorge follows the shoreline of a prehistoric lake, rich in fossils and early hominin sites. Periodic flows of volcanic ash from Olmoti and Kerimasi helped to ensure preservation of the fossils in the gorge.
The locality is significant in showing the increasing developmental and social complexities in the earliest Hominina, largely revealed in the production and use of stone tools. Prior to tools, evidence of scavenging and hunting can be noted—highlighted by the presence of gnaw marks that predate cut marks—and of the ratio of meat versus plant material in the early hominin diet. The collecting of tools and animal remains in a centralised area is evidence of developing social interaction and communal activity. All these factors indicate an increase in cognitive capacities at the beginning of the period of hominids transitioning to homininina—that is, to human clade.
Homo habilis, probably the first early human species, occupied Olduvai Gorge approximately 1.9 million years ago (mya); then came a contemporary australopithecine, Paranthropus boisei, 1.8 mya, followed by Homo erectus, 1.2 mya. Homo sapiens, which is estimated to have emerged roughly 300,000 years ago, is thought to have occupied sites in the gorge 17,000 years ago.
History Discovery and research
While travelling in German East Africa in 1911 to investigate sleeping sickness,Maier, Gerhard, African Dinosaurs Unearthed: The Tendaguru Expeditions, Indiana University Press, 2003, German physician and paleontologist Wilhelm Kattwinkel visited Olduvai Gorge, mistakenly naming it Oldowan , where he observed many fossil bones of an extinct three-toed horse. Inspired by Kattwinkel's discovery, German geologist Hans Reck led a team to Olduvai in 1913. There, he found hominin remains which were later radiocarbon dated to 17,000 BP. Four more expeditions were planned, but World War I prevented their start. After the war, as Tanganyika came under British control, Louis Leakey visited Reck in Berlin and viewed the Olduvai fossils. Louis Leakey became convinced that Olduvai Gorge held stone tools, thinking the deposits were of similar age to the Kariandusi prehistoric site in Kenya. Reck and the paleontologist Donald McInnes accompanied Louis Leakey in his 1931 expedition, where Louis found a number of hand axes close to camp soon after their arrival. Mary Leakey first visited the area in 1935, joining Louis and Percy Edward Kent. Subsequent visits were made by the Leakeys in 1941, 1953, 1955 and 1957.
Louis and Mary Leakey are responsible for most of the excavations and discoveries of the hominin fossils in Olduvai Gorge. In July 1959, at the FLK site (the initials of the person who discovered it Frida Leakey, and K for korongo, the Swahili language word for gully), Mary Leakey found the skull of Zinjanthropus or Australopithecus boisei. In addition to an abundance of faunal remains the Leakeys found stone tools Mary classified as Oldowan. In May 1960, at the FLK North-North site, the Leakeys' son Jonathan found the mandible that proved to be the type specimen for Homo habilis.
Archaeology and geology Hans Reck and Richard Hay While Hans Reck was the first geologist to attempt to understand the geology of the gorge, current understanding of the geology of the stratigraphic sequence of Olduvai Gorge was made possible in large part by the efforts of geologist Richard Hay. Hay spent twelve years studying the geology at Olduvai, much of it working along with Mary Leakey, finally formulating a detailed picture of the geologic history of the area. Hay's seminal work The Geology of the Olduvai Gorge was published in 1976.
Reck identified five main layers of deposition in the gorge, which were labelled Beds I through V, with Bed I being the oldest and lowest in the sequence. Hay and other geologists working at the gorge since Reck's time have utilized Reck's original Bed outline, adding clarity, detail, and corrections to achieve a more thorough understanding of gorge history. Reck's original Bed IV interval was later distinguished as consisting of Bed IV and the Masek Beds, while Bed V has been reclassified as the Ndutu Bed and the Naisiuiu Bed.
Gorge stratigraphy The stratigraphic sequence in the gorge is up to thick, with a welded tuff, the Naabi ignimbrite, forming the base. This is overlain by a series of lava flows from Olmoti and from another source to the south. The oldest fossils are found on this surface, dated at 1.89 mya, while stone tools have been dated at 1.7 mya through the first use of K-Ar dating by Garniss Curtis. In addition, fission track dating and paleomagnetism were used to date the deposits, while amino acid dating and Carbon-14 dating were used to date the bones. Hominid fossils and stone tools are found continuously throughout the entire exposed sequence in the gorge. Faulting between 100 and 30 kya, formed the Olbalbal Depression northwest of Ngorongoro.
Bed I The thick Lower Pleistocene Bed I sediments overlying the Naabi ignimbrite consist of layers of Olmoti tuff and lake sediment claystone. Four well-preserved living sites of note are located within Bed I, the FLK and FLK North-North sites mentioned above, plus DK and FLK North. The DK site (Donald McInnes' first initial plus k for korongo) has what Leakey considers to be a stone circle, and also many tools and fossil bones ranging in age from 1.75 mya to 1.9 mya.
Bed II Bed II consists of of clay and sandstone Olduvai Lake and stream deposits. Manuports are abundant at the MNK (Mark Nicol Korongo) site in addition to a chert nodule quarry containing over 14,000 pieces, including gneiss and lava anvils and hammerstones. Hand axes were found at the EF-HR (Evelyn Fuchs-Hans Reck) and TK (Thiongo Korongo) sites. The BK (Bell's Korongo) site contained an Australopithecus boisei deciduous molar and canine.
Bed III The distinctly red Bed III consists of of clays, sandstones and conglomerates signifying variable lake depths. Few fossils are present and only isolated stone tools, indicating a sparse early man presence.
Bed IV Bed IV is a distinctly different unit from Bed II in the eastern portion of the gorge. There, it is thick and composed of clays, and stream deposited sandstones and conglomerates. Four distinct tool-bearing levels are evident, including 500 handaxes and cleavers at the HK (Hopwood's Korongo) site, while phonolite handaxes and an elephant bone handaxe were found at the HEB (Heberer's Gully) site. The WK (Wayland's Korongo) site contained a Homo erectus pelvis and femur.
Masek beds The Masek Beds are composed of two episodes of aeolian ash from Kerimasi. A number of quartzite handaxes were found in this layer at the FLK site. Dunes formed after the deposition of Oldonyo Lengai tuffs make up the upper portion of the Ndutu Beds, but yield few fossils. Oldonyo Lengai tuffs also make up the Naisiusiu Beds.
Associated fossil species The few Australopithecus boisei remains, which include the skull, a thigh bone fragment, and several teeth, were found distributed throughout Beds I and II, which dates them in the range 1.1 to 2 mya. The more common remains of Homo habilis were found in Bed I and the lower portion of Bed II, which makes them contemporaries of Australopithecus boisei. Homo erectus remains were found in the upper portions of Bed II, making them contemporaries of Australopithecus boisei, but not of Homo habilis.
The stone tools and their makers
Louis Leakey first described the Oldowan stone tool industry in 1951. The Leakeys determined that choppers were the most common stone tool found at the gorge, amounting to over half of the total number, and identified 11 Oldowan sites in the gorge, 9 in Bed I, and 2 in Bed II. They also identified the Developed Oldowan as the subsequent diverse tool-kit found in Beds II, III, and IV, with small tools made mostly from chert rather than quartzite. These tools are mostly spheroids and sub-spheroids, followed by choppers.
Besides the chert quarry in Bed II, the Leakeys were able to identify the other source locations of the principal rocks used to make the stone tools. The most common material was quartzite, which originated from the Naibor Soit Inselberg just north of the gorges. The phonolite originated from the Engelosen volcano 5 km to the north. The gneiss came from the Kelogi inselborg 9 km to the southwest.
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 diet of tough plant material, including tubers, nuts, and seeds—and possibly large quantities of grasses and sedges.
Conversely, the Leakeys' 1960s finds presented different characteristics. The skull lacked a sagittal crest and the braincase was much more rounded, suggesting it was not australopithecine. The larger braincase suggested a larger brain capacity than that of Australopithecus boisei. These important differences indicated a different species, which eventually was named Homo habilis. Its larger brain capacity and decreased teeth size pointed to Homo as the probable toolmaker.
The oldest tools at Olduvai, found at the lowest layer and classified as Oldowan, consist of pebbles chipped on one edge. Above this layer, and later in time, are the true hand-axe industries, the Abbevillian and the Acheulean. Higher still (and later still) are located Levallois artifacts, and finally the Stillbay implements. Oldowan tools in general are called "pebble tools" because the blanks chosen by the stone knapper already resembled, in pebble form, the final product.Napier, John. 1960. "Fossil Hand Bones from Olduvai Gorge." in Nature, December 17th edition. Mary Leakey classified the Oldowan tools according to usage; she developed Oldowan A, B, and C categories, linking them to Modes 1, 2, and 3 assemblages classified according to mode of manufacture. Her work remains a foundation for assessing local, regional, and continental changes in stone tool-making during the early Pleistocene, and aids in assessing which hominins were responsible for the several changes in stone tool technology over time.
It is not known for sure which hominin species was first to create Oldowan tools. The emergence of tool culture has also been associated with the pre-Homo species Australopithecus garhi, and its flourishing is associated with the early species Homo habilis and Homo ergaster. Beginning 1.7 million years ago, early Homo erectus apparently inherited Oldowan technology and refined it into the Acheulean industry. .