Situated in Masai, northern Tanzania (in the Great Rift Valley on the eastern Serengeti Plain), Olduvai Gorge is an impressive gorge and side-gorge structure around 40 Kilometres (25 miles) long and 100 metres (295 feet) deep. It was formed 70,000 years ago when a river began cutting through the sediments deposited by an ancient lake basin; the rocks beneath it are around 5.3 million years old. Olduvai Gorge is effectively an archaeological archive as its fossil record extensively covers the past two million years (2,100,000 to 15,000 years ago, to be precise). It has supplied information on the over 50 hominids who are interred there and contains the longest known record on the use of stone tools; it is with good reason that it is referred to as the ‘Cradle of Mankind’ and protected by the borders of the Ngorongoro Conservation Area.
It was first discovered - and I use the expression liberally here - in 1911 by Wilhelm Kattwinkel (also written ‘Katurinkle’), a German entomologist who was in search of butterfly specimens. The first excavation was conducted by the English palaeoanthropologist Louis Leakey (who came to be known as ‘the Old Man of Olduvai’) in 1931; he was allegedly inspired by fossils collected from the site in 1913 by the German geologist Hans Reck. These activities were encouraging, as there was an abundance of early stone tools and animal fossils. These tools included those from the Oldowan industry of the Lower Palaeolithic (where there is the first evidence of tools being made with specific purposes in mind) and the Acheulian industry (which originated 500,000 years ago); these are the oldest known tool conventions in human history. Subsequent expeditions over the decades were undertaken in the attempt to find human fossils.
The first of these were discovered in 1959 by Mary Leakey. This find came in the form of a 1.8 million year old skull in 400 tiny pieces, originally belonging to an australopithecine called Zinjanthropus (reclassified as Australopithecus or Paranthropus) boisei, or ‘Zinj’, as it is colloquially known. This discovery was one of the catalysts for wide-scale research of human activity in Africa. Later discoveries were made by Jonathan Leakey from 1960 onwards; his efforts yielded the then-oldest known fossil of the human genus (presumed to be the origin of the stone tools discovered at the site), the 1.75 million year old Homo habilis (or ‘handyman’). Hominid teeth, discovered in 1974, have been found to date beyond 2 million years in age.
Inferences made with relation to the fossils abound. The most basic (albeit the most profound) was the addition of evidence to support the theory that humankind originated in Africa in a ‘womb-like’ environment. Another suggests that depopulation of the area around 600,000 years ago was the product of an abrupt climate change which created a dry savannah. Others still analyse behavioural patterns: early hominids did not live in large groups and a disproportionately large number of males undertook hunting or scavenging activities. Studies of tooth structures suggest that plant foods were the dominant part of their diet and that they slept on rock faces or in trees as a means of protection from predators. The number and diversity of tools varies between beds, but there is a natural progression towards increasing complexity and diverse use of whatever materials were available at each individual site. Further analysis of proto-human behavioural patterns comprises the bulk of modern studies in the area.
There are seven clearly separate (major) fossil beds, ranked in order of age: Bed I is 2.1 million years old and 60 metres (197 feet) thick. Composed largely of volcanic matter (ash and lava flows) as well as some other sediments, it contains evidence of fauna and the Oldowan industry. There have been some butchery and campsites discovered here (in areas where streams from the highlands carried fresh water to Olduvai Lake).
Bed II varies in thickness from 20 to 30 metres (66-98 feet) and is 1.7 to 1.15 million years in age; it contains two distinct divisions of rock layer (upper and lower) and while the lower is similar in composition to Bed I, the upper part contains a larger amount of sediment and was formed after the ancient lake had been reduced in size by fault shifts. Alongside many fossilised human remains (see above), the Acheulian industry is evident.
Beds III and IV were created pursuant further fault shifting and erosion and they range from 1.15 million to 600,000 years in age. They are indivisible, save in the eastern part of the gorge and are, at maximum, 30 metres in thickness. They consist mainly of stream sediments. Many living sites once situated in Beds II-IV are thought to have been eroded away by water (as they generally sat in past stream channels).
The Masek Beds contain only one remarkable archaeological site and it too is of the Acheulian industrial period. Comprised mostly of stream sediments, the Masek Beds formed during a period of intense geological activity and it is thought that the climate of the time must have been similar to that of today. They are 25 metres (82 feet) at their greatest thickness.
The Ndutu Beds, comprised largely of Aeolian tuff, contain two Middle Stone Age sites and are the 32,000 year old product of faulting, erosion and inundation of the gorge.
The Naisiusiu Beds are the youngest and are only 11 metres (33 feet) in thickness, also comprised of Aeolian tuff. One site contains microlithic tools and the other a complete Homo sapiens skeleton; both are 17,000 years in age.
The site and its museum displays are open for public perusal. Other destinations of interest within the area are the Laetoli site, Lake Ndutu sites and Nasera Rock Shelter.
Sources:Archaeology: the Definitive Guide, various authors.
http://www.sfu.ca/archaeology/museum/olduvai/index2.html (‘Olduvai Gorge, 1969’ - this site contains a wealth of images).
http://www.mnsu.edu/emuseum/archaeology/sites/africa/olduvai_gorge.html (‘Olduvai Gorge’, Allen Caldwell).
http://studentweb.tulane.edu/~sau/Olduvai.htm (‘Olduvai Gorge: a study of Oldowan culture and hominid activities’).
http://www.bobbytours.com/olduvai_gorge.htm (‘The Northern Circuit Tour’).
http://www.bartleby.com/65/ol/OlduvaiG.html (‘The Colombia Encyclopaedia, Sixth Edition, 2001’).
http://www.utalii.com/Ngorongoro/Olduvai_Gorge.htm (‘Talii Travel - Tanzania, the Heart of Wilderness’).
http://www.britannica.com/ (‘Encyclopaedia Britannica - the online encyclopaedia you can trust!’).