Olduvai Gorge

The Olduvai Gorge is a steep-sided ravine in the Great Rift Valley that stretches through East Africa. It is in the eastern Serengeti Plains in northern Tanzania.

The gorge is about 48 kilometers (30 miles) long. It was once a lake, and got covered by layers of volcanic ash.Hay, Richard L. 1976 Geology of the Olduvai Gorge. University of California Press. 

Olduvai Gorge is a highly important prehistoric site for the study of human evolution. This site was occupied by Homo habilis about 1.9 million years ago, Paranthropus boisei 1.8 million years ago, and Homo erectus 1.2 million years ago. Homo sapiens occupied the site 17,000 years ago. Scientists have learned a great deal about human evolution by studying fossils and artifacts found at Olduvai Gorge.

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.

 Geology 
Millions of years ago, the site was a large lake, whose shores were covered with successive deposits of volcanic ash.

About 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 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.

The stratigraphy is extremely deep and layers of volcanic ash and stones allow radiometric dating of the embedded artifacts, mostly through potassium–argon dating and argon–argon dating. The base of the Olduvai sediments dates to slightly older than 2 million years,Walter R.C. et al 1992. Tephrochronology of Bed I, Olduvai Gorge: An application of the laser-fusion 40Ar/39Ar dating to calibrating biological and climatic change. Quaternary International 13-14, 37-46.

Olduvai Gorge is  from the Laetoli archaeological site, which has a much older fossil record.Drake R. & Curtis G. 1987. K–Ar geochronology of the Laetoli fossil localities. In: Leakey M.D. & Harris J.M. (eds) Laetoli: a Pliocene site in northern Tanzania. pp48-52. Claredon Press, Oxford.

 Palaeontology 
Olduvai Gorge is one of the most important prehistoric sites in the world. It has greatly increased our understanding of early human evolution. 

 First discovery 
The discovery of fossils and artifacts at Olduvai Gorge happened accidentally. According to a 1961 Time magazine article:Chasing a fancy butterfly in the green wilds of Tanganyika [in 1911], a German entomologist named (Wilhelm) Kattwinkel tumbled off a rocky ledge and nearly killed himself. When he regained his senses, he found himself in an anthropologist's dream world: an erosion-created rift with layer after layer of fossils, bones and ancient artifacts. The find was named Olduvai Gorge, and Kattwinkel's heirs ever since have been scrambling up and down its sun-baked sides in search of clues to man's earliest awakening. http://www.time.com/time/magazine/article/0,9171,826938,00.html  Time.com, Original article dated Friday 10 March 1961

Excavation work there was pioneered by Louis and Mary Leakey beginning in 1931. It is still going on.

 Findings 

 Bed I (the oldest layer) 
In the earliest archaeological deposit at Olduvai Gorge, known as Bed I, scientists have found evidence of campsites and living floors. They have also found stone tools made of flakes from local basalt and quartz. These tools were named Oldowan because they were first discovered at Olduvai Gorge. However, archaeologists later found older Oldowan-style tools at other archaeological sites. Scientists now believe the Oldowan toolmaking tradition started about 2.6 million years ago.

Bones found in this layer do not come from modern humans. They come from earlier hominid forms of Paranthropus boisei and the first discovered specimens of Homo habilis.

At a site called FLK North, there is evidence that Homo ergaster used stone tools to butcher and eat elephants around 1.8 million years ago. This is the earliest known evidence of elephant consumption by archaic humans. At the lowest of Bed I's six layers, archaeologists found a nearly complete skeleton of the extinct elephant species Elephas recki. Nearby were stone tools like choppers and flakes, which early hominids would have used to butcher meat. Large numbers of bone fragments of smaller animals found with it clearly identify FLK North as an early butchering site.Chazan, Michael 2008. World prehistory and archaeology: pathways through time. Pearson. p95 

 Bed II 
Above this, in Bed II, pebble tools begin to be replaced by more sophisticated handaxes of the Acheulean industry and made by H. ergaster. This layer has not yet been successfully dated, but likely falls between 1.75 and 1.2 million years.McHenry H.M; Brown C.C. & McHenry L.J. 2007. Fossil hominin ulnae and the forelimb of Paranthropus. American Journal of Physical anthropology 134: 209-218.

 Beds III and IV 
Beds III and IV have produced Acheulean tools and fossil bones from more than 600,000 years ago.

During a period of major faulting and volcanism roughly 600,000 to 400,000 years ago, the Masek Beds were made. These beds contained tools from an industry made by modern humans, followed by the Ndutu Beds (400,000 to 32,000 years ago), and the Naisiusiu Beds (22,000 to 15,000 years ago).

Also, on the rim of the Gorge, is the Olduvai Gorge Museum. This Museum presents exhibitions about the Gorge's history.

 References 

Category:Geography of Tanzania
Category:Archaeological sites in Africa
Category:Prehistoric Africa