31 Olduvai Gorge

Ranjana Roy

Introduction

Olduvai Gorge is a very important site located in Tanzania, east Africa. The place’s importance lies in the fact that it has yielded uninterrupted history of evolution of biology and culture from the very beginning of human kind.

Olduvai Gorge lies on Serengeti Plain within the boundary of Ngorongoro crater and its conservation area. UNESCO designated it as a world heritage site. The steep gorge formed along the banks of the upper reaches of Olduvai River exposed geological strata from Tertiary into Quaternary. From the exposed beds biological and cultural remains of early men are found in a datable context.

Olduvai Gorge is made famous by Louis S. B. Leakey, a British Palaeoanthropologist who was born in Kenya, Africa but was trained in Cambridge University, England in Anthropology and Archaeology. He got his doctoral degree in African prehistory. The site Olduvai Gorge was intensively worked by Louis Leakey from 1931 onwards. Both Louis Leakey and his wife Mary Leakey and later on their sons Jonathan and Richard continued with exploration and excavation in east Africa. Olduvai Gorge yielded more than 60 hominid fossils and countless stone tools made by early men.

Unique Geographical Location of Olduvai Gorge

Olduvai Gorge is located on the Great Rift Valley. It is a wide flat plain in East Africa formed approximately 20 to 25 million years ago. Due to plate movement along the faults in East Africa land went down and volcanoes were formed, which erupted. The great Serengeti Plain and Ngorongoro crater is a part of the formation within which lies Olduvai Gorge. The valley floor is nearly 100 kms wide. At present the land is made up of mountains, valleys and lakes. The lines of faulting pass through the great lake region. Out of the two faulting lines, the Western line is marked by Lake Albert, Edward, Kivu and Tangnyika. The eastern line of faults is marked by volcanoes, such as Kenya and Kilimanjaro and a number of small lakes such as, Nakuru, Navaisha, Magadi and Eyasi(see map).

At the early phase of Quaternary prehistoric men witnessed widespread tectonic movement because of which not only volcanoes erupted but land surface and even courses of water bodies were changed. However, abundant fossil and cultural remains suggest that the area was inhabited by early man.

Quaternary climatic sequences of East Africa

According to G. Mortelmans, a famous geologist, the water bodies of the lakes of the rift valley served as a “pluviometer “of gigantic scale (Aliman, 1957: 197). ‘Pluviometer’ means measuring unit for understanding climatic conditions during Pleistocene period. Africa had undergone alternating wet and dry phases during Pleistocene. The wet phases are known as pluvial and the dry phases lying in between two pluvial phases are known as inter pluvial phases. A number of scientists, including L. S. B. Leakey had worked on the Quaternary climatic sequence and it was resolved in the third Pan African Congress, held in Livingston in 1955 that Kageran, Kamasian, Kanjeran, Gamblian, Makalian and Nakuran should be recognized as stratigraphic climatic divisions in East Africa (Clark, 1957: xxxi). Kageran was the earliest and Gamblian the last one during Pleistocene period. Major beds (Bed I– IV) at Olduvai Gorge yielded evidences of Kamasian and Kanjeran pluvials.

Stratigraphic sequence at Olduvai Gorge

Olduvai Gorge presents an excellent cross section of Kamasian pluvial deposit belonging to Middle Pleistocene time period. Wall of the gorge is over three hundred feet high. It has cut through the Serengeti Plain and has exposed the deposits of Kamasian lake of earlier times. Fossils and artifacts were found from all the layers (picture 2).

Basaltic rocks lie at the base of the Gorge. On the basaltic base of the Gorge several superposed beds were found by Leakey (1974). Olduvai Gorge is divided into seven successive formations (Hay, 1976). From oldest to Youngest, they are as follows: Bed I, Bed II, Bed III, Bed IV, the Masek beds, Ndutu beds and Naisiusiu beds. These beds provide relatively complete record of Pleistocene period from about 2.1 million years ago to 15,000years B.P. Sediments of Holocene, less than 10,000 years B. P. are present in and near the Olduvai Gorge. Following is description of the beds after Leakey mostly.

Bed I is the lowest and the thickest deposit. Its average thickness is 60 meters. The bed consists of Lava. Sedimentary layers lie over lava. Bed I is dated by Potassium-Argon method. Bed I at the western part of the main Gorge is oldest and the dates range from 2.0 to 2.1 million years ago. Top of Bed I is 1.7 million years old. It appears that the entire tool bearing areas and faunal remains came from the upper part of Bed I and belongs to dates ranging between 1.85 to 1.7 million years of age. Bed I is divided into five strata or layers. These are made up of clay stone and volcanic ash deposit of Ngongoro volcano. Leakey termed the deposit as lacustrine marl. Bed I yielded tools belonging to Oldowan industry. This industry is divided into four evolutionary stages. Louis Leakey’s wife Mary Leakey discovered a hominid fossil from this bed. This was first named as Zinjanthropus boisie and later classified as Paranthropus boisie. Palaecology of the time of formation of lower part of Bed I showed that forested environment surrounding a lake prevailed at that time. By the time of deposition of middle portion of Bed I the area had a mosaic environment with open woodland. Trees mingled with grassland surrounded the lake. This indicated that climate was changing to drier condition. Early hominines roamed the land at this time. Upper part of Bed I records a farther drying trend with open landscape which announced the beginning of a dry period.

Bed II is found lying over Bed I. It is quite difficult to distinguish the contact zone between the two beds. Thickness of Bed II varies between 20 to 30 meters. Bed II is spread over a wider area than Bed I. There are two subdivisions of Bed II. Each of the subdivisions is distinct in their geological characters and in sequence of deposit of tuff (volcanic ash). Bed II in its lower part had common environmental element with Bed I, having more water in the lake and with the presence of swamps. In later parts of the Bed II a gradual increase in grassland and shrinkage of lakes are evident. Savannah type fauna prevailed at this stage. Bed II is dated to 1.7 to 1.15 million years ago. Onset of dry climate in Bed II is detected around 1.6 million years back. Remains of Homo habilis are recovered from the lower part of Bed II. Homo ergester, the African type of Homo erectus, remains came from the upper part of Bed II. One interesting fact is to be noted that remains of Paranthropus boisie are found from both lower and upper parts of Bed II. This Indicated that all the three types of hominines lived at Olduvai simultaneously. A Group of artifacts designated as Chelles-Acheulian industry was recovered from Bed II. Approximately around 1.15 million years back a wide spread faulting took place in Olduvai basin, eroding Bed II and bringing about considerable change in palaeo-geography of the region. This bed showed evidence of cultural change from Oldowan to Acheulian type of culture. Bed III and Bed IV were subsequently deposited over the changed surface of the Olduvai basin.

Bed III varies in thickness from 10 to 15 metres (Alimen, 1957: 201).The deposit is reddish brown in colour and is made up of volcanic detritus material (Hay, 1976:27). This bed was laid from 1.15 million years back to 0.80 million years ago. Shrinkage of lake and aridity suggest dry inter pluvial climate. Acheulian industry is recovered from the site.

Bed IV is dated from 0.80 million years to 0.60 million years ago. Bed IV was formed with loads deposited from the streams, when wet condition set in and river had more water. The bed was formed during Kanjeran pluvial period. Increase of water in lake is indicated by rise of lake level. Rising water level left its mark along the shore of the water body. This indicated onset of the wet pluvial period. Bed IV yielded artifacts of Typical Acheulian industry.

Leakey discussed about Bed V, which is considered to have formed under a condition of severe earth movement, resulting in faulting and eroding of Beds I to IV successively. This happened at a time of inter pluvial period between Kanjeran and Gamblian pluvial. Hay (1976) distinguished three more beds.

Masek bed is 400,000 to 600,000 years old. This bed was laid before the formation of the Gorge. One Acheulian site is found in it.

On Masek bed lays Ndutu bed about 32,000 to 400,000 years old. Lower part of the bed dates to 40,000 to 60,000 years before present. Tools of Middle Stone Age are found from this bed.

Naisiusiu bed was formed when upper limit of Ndutu bed was eroded and the Gorge was formed and reached to its present depth. This bed is made up of wind borne volcanic ash. The bed is dated by C14 method to 22,000 to 15,000 B.P. Homo sapiens remains and microliths are found from this bed.

Climatic condition at Olduvai Gorge fluctuated between wet pluvial and dry inter pluvial periods. Olduvai Gorge is situated on the great rift valley of East Africa. Presence of faults caused several large scale earth movements. However the area attracted a variety of mammals, especially medium sized antelopes. Early men lived in the lake shores and along the fresh water streams.

Palaeoanthropology and Olduvai Gorge

Olduvai Gorge has given proper understanding of human evolution for the first time. L. S. B. Leakey, Mary Leakey and their sons discovered hominine remains from Olduvai Gorge. Later on teams from Tanzania and from America made important discoveries of fossils of early human beings.

First discovery was made in 1959 by Mary Leakey of the hominid labeled as OH5, which was nicknamed as “Nutcracker Man” because of the large size of its molar teeth. It was 1.75 million years old, had a flat face, huge teeth, a large crest on the top of his head and a small brain. Leakey named it as Zinjanathropus boisie. It is known at present as Paranthropus boisie (fig. 1).

Mary Leakey and her son Jonathan Leakey discovered the remains of another hominid in 1960. It was labeled as OH 7 (fig. 2). It was found 300 yards away from the place where nutcracker man’s remains were found. The skull had a significantly larger brain (680 CC). Leakey also found some hand bones and skull fragments from the same place as OH 7. Hand bones showed that the hominid was capable of precision grip, which is considered as capacity for fine manipulation of objects with its hands. Leakey named the hominid as Homo habilis meaning ‘handy’ man because he used to carry stones with his hands to make tools and pave the floors of his habitation ground. Richard Leakey, another son discovered another Homo habilis in 1972. Homo habilis was dated to 1.9 million years ago. In 1960 a well preserved foot, labeled as specimen no. OH 8, was discovered at Olduvai Gorge. The foot belonged to Homo habilis. It had modern looking foot arches, showing that it had a bipedal gait and walked like modern man. Probably it was attacked by a crocodile. A full skull of Homo habilis was found in 1968. It was nicknamed as “Twiggy” (OH 24).

Fig. 2. Homo habilis lower jaw remains, Lower jaw of OH 7 found in 1960 at Olduvai Gorge and identified by Louis Leakey and others in 1964 as a fossil of Homo habilis.

(http://www.britannica.com/EBchecked/topic/427425/Olduvai-Gorge)

Leakey discovered a skull cap labeled as OH 9. It is also known as Chellean Man. It was dated to be 1.9 million years old. Though it was discovered in the same year as the discovery of Homo habilis, it was found that the specimen has a cranial capacity of 1,065 CC (cubic centimeter), much bigger in size than Homo habilis. The skull had thick brow ridges and a low sloped forehead. Leakey placed it in the group Homo erectus (Fig. 3).

Another incomplete skull cap labeled as OH 12, also known as “Pin head” Man was discovered at Olduvai Gorge in 1962. It is similar OH 9 but had a smaller brain size 750cc and dates between 800,000 and 120,000 years old. Homo erectus of Africa is designated as Homo ergaster.

 

Fossil remains of Olduvai Gorge have placed the site as the Homeland of Mankind. Beginning from 2 million years Paranthropus, Homo habilis and Homo ergaster Species evolved and roamed the grounds of Olduvai basin.

Archaeological remains from Olduvai Gorge

Stone Age sequence in Africa differed from those of Europe. The African sequence follows the order as follows (Clark, 1957).

Early Stone Age

First Intermediate

Middle Stone Age

Second Intermediate

Late Stone Age

Olduvai Gorge had yielded cultural remains of Early Stone Age from the pluvial and interpluvial sequences of Kamasian and Kanjeran (Fig. 4 –Oakley: 180). The Oldowan culture was first recognized by Leakey in Bed I of Olduvai Gorge in Tanzania. The industry is placed to the upper part of Lower Pleistocene. Around 2 million years ago the first species of Homo habilis started to make tools. These are made by Mode 1 type technology and are classified as Oldowan tools and the culture is known as Oldowan culture. Hominine group named as Paranthropus boisei was dated to 1.8 miilion years ago. It appeared that at Olduvai Gorge both Homo sp, and Paranthropus were present simultaneously. The latter disappeared about 1 million years back. Tool making was done by the Homo species.

Oldowan culture

The Oldowan tools are mostly made on pebbles of lava and quartz. The pebbles were struck with the intention for getting the sharp end along one edge. These are known as choppers (fig. 5). The raw material for tool making was procured from a distance of 19 km. This indicated the cognitive capacity of early Homo for the deliberate choice of suitable raw materials for making Oldowan tools, meaning that they searched for the raw materials and carried them to their place of work. Oldowan culture flourished from Bed I into lower part of Bed II. Oldowan people lived through a dry phase in a savannah type environment. The tools probably were used as missiles as well as for chopping purposes.

Chelles-Acheulian culture

At Olduvai tools were collected layer by layer from the exposed sections of the Gorge (Leakey, 1951). It was found that a good percent of pebble tool in Bed II were advanced types. These were worked more extensively by removing flake scars in more than two directions and then in other directions. Finally giving rise to a biface or hand axe. These are called biface because they were worked on both the faces. There is a clear cut evidence of advancement and evolution of Oldowan culture into biface culture. Leakey preferred to call this stage as Chelles-Acheul culture. The Chellean culture is also known as advanced Oldowan culture in Olduvai Gorge. Tools of Chelles –Acheul culture are pointed in outline or pear shaped or oval in outline. These have wavy or zigzag margin formed by the intersection of deep flake scars from both the surfaces. Leakey divided Chelles-Acheul culture into 11 evolutionary stages from Bed II into Bed III and subsequently into Bed IV (fig. 4. Oakley, 1964: 180). The assemblage at each level yielded different types of finished artifacts as well as handaxes, pebble tools, flakes and flake tools. Pebble tools were gradually decreasing in frequency of occurrence. Technique of manufacture of tools of Chelles-Acheul culture was direct percussion method. Flaking was done by hammer stone, stone anvil or block on block method. That means the tools were fashioned by directly hitting the stone with another stone. Chellean handaxes are very coarsely made. The tools are made on pebble and they grade into pebble tools showing their origin in Oldowan culture (fig. 6).

Acheulian stage is distinguished from the Chellean by means of a new flaking technique and with the advent of new types of handaxes. In Olduvai Gorge transition from Chellean to Acheulian is marked in stages 4 and 5. The transition is from advanced Oldowan into Acheulian stage. Acheulian handaxes were mostly pointed or oval and symmetrical in shape (fig. 7). The lateral margins are formed by the removal of small shallow flake scars. Acheulian handaxes were made or at least finished by cylinder hammer technique. Although Acheulian men used a variety of raw materials but the finished products remained symmetrical, efficient and showed beautiful craftsmanship. A new type appeared with an axe like transverse end instead of a pointed end. These bifaces are known as cleavers. These cleavers have been tested on meat, wood and other objects. The experiment showed that the cleavers were very efficient tools for skinning and cutting meat off the carcasses. Cleavers appeared in Acheulian stage (fig. 8).

Acheulian is the techno complex attached to Homo ergaster/ homo erectus that appeared in Eastern Africa 1.7 miilion years ago, reflecting greater cognitive, economic, social, and territorial complexity. Acheulian represents a substantial technological advancement over Oldowan. Stone workers now had the ability to produce large flakes (over 10cm long) and could make large artifacts such as handaxes or bifaces, the knapping of which demanded minute knapping of a large flake on both sides. This careful working produced a cutting edge along most of the axe border. The large formats of Acheulian tools served several purposes including the butchery of large animals such as elephants, and hippopotami (which would have required a great deal of force) and woodworking. Acheulian technology was one of the most remarkable of all the palaeolithic techniques. It lasted almost over 1.5 millions of human evolution, extended across the old world and formed the basic technological equipment for many and very different human species.

Palaeolithic Living sites in Olduvai Gorge

A number of living sites were discovered at Olduvai Gorge (fig. 9, Oakley 1968: 185). Early man in Olduvai Gorge lived basically on gathering of nuts, tubers and other vegetable food. Meat formed a small part of their diet. Fish, birds and large mammals’ bones are left by early men at the site known as FLK -Zinj. There is a debate whether men in Olduvai Gorge were scavengers or hunters. They could be either or both.

Summary

Olduvai is a deep gorge formed along the bank of Olduvai River at its upper reaches. It is located on the Great Rift Valley in East Africa. Due to the presence of faults, the area experienced severe earth movement from time to time. Geologists identified seven beds along the walls of the Gorge. Earliest deposit dates to 2.1 million years ago. The beds were deposited through Kamasian and Kanjeran pluvial and interpluvial periods in between. Bed I is the lowermost deposit. It was formed at a time when climate was becoming dry after the Kageran pluvial. During pluvial times the lake had more water and forests prevailed. Lakes shrunk in size and forest was replaced by open savannah type grassland. Early hominids lived along the lake shores. Leakey family and their teams and later on Teams from Tanzania and America researched layer by layer at Olduvai and discovered an unbroken and continuous evidence of human evolution, both biological and cultural. First hominid found was Paranthropus boisie and after that skull fragments, foot and hand bones of fossils were found, which had all the characteristic features of Homo and was called Homo habilis. Homo habilis appeared in Bed I and lived into lower part of Bed II, mostly through dry savannah type grassland. They made Oldowan industry. Tools of the industry were simple pebble tools made on lava and quartz, produced with the use of percussion, stone hammer or block on block technique. Oldowan culture developed through time into advanced forms and gave rise to bifacially worked handaxes and cleavers. This phase is marked by the appearance of Homo ergaster/ Homo erectus. Throughout the upper part of Bed II, Bed III and IV biface culture evolved. Crude and coarse Chellean hand axes evolved into finely made Acheulian handaxes. Chellean handaxes were made by stone hammer technique. Acheulian handaxes were finished by cylinder hammer technique. Cleavers appeared towards later part of Acheulian industry. Middle Stone Age industry came from Ndutu bed around 60,000 years ago. Homo sapiens remains were found from Naisiusiu bed around 17,000 years back and were associated with microlith industry. The painstaking works of archaeologists, anthropologists and geologists revealed the unbroken history of human evolution at Olduvai Gorge. However, not only Olduvai Gorge but the primordial Eve who gave rise to modern population was identified in East Africa. Olduvai Gorge is known as “cradle land of Mankind”.

References

• Aliman, H. 1957. The Prehistory of Africa. English translation by Hutchinson, Scientific & Technical, London.
• Clark, Desmond. 1957. Third Pan – African Congress on Prehistory: Livingstone 1955. Chatto & Windus, London.
• Hay, Richard L. 1976. Geology of the Olduvai Gorge: A Study of sedimentation in a semiarid basin. University of California Press.
• Leakey, L. S. B. 1951. Olduvai Gorge. Cambrige University Press. Cambridge.
• Leakey, L. S. B. 1974. By the Evidence: Memoir (1932 – 1951). Harcourt Brace, Jovanavich, New York.
• Oakley, Kenneth P. 1968. Frameworks for Dating Fossil Man. Aldine Publishing Company, Chicago.

Further Reading

• Ember, Carol R., Ember, Melvin and Peter N. Peregrine, 2003. Anthropology. Pearson Education (Singapore) Pte. Ltd. Indian Branch, 482 F. I. E. Patparganj, Delhi 110 092, India. Chapters 6 & 7.
• Leakey, L. S. B. 1951. Olduvai Gorge. Cambrige University Press. Cambridge.
• Oakley, Kenneth P. 1968. Frameworks for Dating Fossil Man. Aldine Publishing Company,Chicago.
• Website Encyclopaedia Britanica http://www.britannica.com/EBchecked/topic/427425/OlduvaiGorge