The palaeolandscape of the area that is now Sibiloi National Park would have looked a little different two million years ago. A different lake occupied the basin at that time, named the Upper Burgi Lake in the geological record. By 1.8 million years this lake had either dried or filled up with sediment and instead a slow, meandering river flowed southwards through the basin. The river would have been lined with riverine tropical forest with abundant fruiting trees and interspersed with swampy grasslands.

By studying the fossil mammals through time we can interpret the habitat and at about 1.8 million years ago the habitat shows an increase in the abundance of open country animals. The lake and the rivers still contained an abundance of fish, crocodiles and hippos although some of these animals looked quite different to their modern day counterparts.

In the distance active volcanoes stood out on the horizon, erupting every so often and in doing so would throw volcanic ash high into the air. This either settled as dust or was carried and deposited by rivers or in the lake at a muddy bottom. These ash layers are important today in dating the sediments in which fossils are found.

Active volcanoes stood among hills to the east of here periodically blowing out clouds of ash. A permanent river flowed through this area, bringing sediments and ash from the hills. This material settled on a large delta, which was building out into the lake, moving the shoreline steadily westwards. Smaller rivers flowing down from the uplands left their sediment on the flat flood plain. [ return to top ]

In the past wildlife was certainly more abundant than it is today as much of the modern day landscape is now inhabited by pastoral people and their livestock. From the fossil record we can see that the forests lining the rivers contained both leaf and fruit-eating monkeys, giant grass-eating baboons called Theropithecines, several species of elephants, a diversity of pigs and different horses. Giraffe, including a peculiar looking short necked form call Sivatherium, a whole array of antelope species, and large-horned buffalo have long since gone extinct. Both black and white rhino were once common and a diversity of carnivores, including the impressive sabre-toothed cat, preyed on the animals that lived in the region.
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Though the water in Lake Turkana is fairly alkaline today, in past times this has varied, depending on the lake size and inflow of fresh water from the north. At certain times very high-salinity lagoons formed along the lake shores, providing the ideal environment for mats of blue-green algae to grow and these can be seen by the trace fossils of stromatolites at several sites on both sides of the modern lake. These algal mats began by growing around a half bivalve shell or pebble and prefer high salinity warm waters, which is hostile to mollusks and other algal eating predators.

Many different mollusk species in habited the lake and rivers, gastropods, clams and fresh water oysters. Several species of turtle lived in the lake and two species of crocodile including the slender-snouted, long-toothed Euthecodon, which has since become extinct. Hippos and fish were in abundance; lungfish, catfish and fresh water stingrays swam the waters, as did numerous Nile perch and Cichlids.

The shoreline of ancestral lake Turkana would have looked similar to places around the lake today where reed beds are prevalent, but otherwise saline-adapted grasses grow along the shore, and beaches providing excellent breeding grounds for crocodile and turtles who come ashore to lay their eggs. [ return to top ]


 Above: The landscape of Sibiloi was wetter and more lush two million years ago, similar to the Masai Mara or Serengeti today. Fossil evidence shows that similar creatures dotted the landscape.

 Two elephant-like Deinotheres are shown here with an unidentified herd of antelope behind them. In the background, a much larger Lake Turkana and an active volcano. One interesting creature appears in the foreground and has remained there ever since: it was during this time that our own genus, Homo, emerged.

"Skull 1470" was perhaps the most significant early find (1970) at Koobi Fora. The skull was and still is one of the very best examples of early Homo, and and prompted the creation of a new species, Homo Rudolfensis, to designate this find, a designation now contested based on new fossil evidence.
Volcanic eruptions have periodically occurred in the vicinity of the lake throughout its existence. The ash from these eruptions would mix with the lake waters and become part of the material deposited on the animal remains near the lake, thus creating a good environment for fossil preservation.
Between two and 1.8 million years ago at least four species of hominid coexisted in the Turkana Basin, namely Australopithecus boisei, Homo habilis, Homo erectus and Homo rudolfensis. Why was there no competition for resources? It is likely that the larger-brained species of our own genus Homo had a better-developed social system and worked as a team to capture animals for food. The Australopithecines ate vegetative matter and other coarse foods as their teeth are well adapted for this due to their large and robust nature. All four species were upright-walking hominids, possibly one of which may be likely to fall more directly on our evolutionary line. Homo erectus  is the first known hominid to walk out of Africa and at about 1.8 million years evidence of Homo erectus  begins to appear outside of Africa, for example in Dmanisi in Georgia. Hominids continued to live in Africa but the expansion of the species range is an indication of the intelligent nature of these beings in exploiting new frontiers.

Several important archaeological sites both on the east and west sides of Lake Turkana throw some light on hominid behaviour and tool use and the sourcing of raw materials for stone tool manufacture. [
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  Stone Tool [enlarge]


Stone tools found during this time interval included sharp-edged flakes, and pointed and serrated cores, made by working a large stone with a hammer stone – also found with the stone tools. Most tools from the Turkana Basin are made of basalt lava, but chert and vein quartz examples have also been found. Such tools may have been used for a wide variety of purposes but we certainly know they were used for the butchery of animal carcasses. Several archaeological sites contain fossilized bone bearing telltale “cut-marks,” rows of fairly thin, parallel cuts on the bones that were marked pre- fossilization, suggesting that the bones were subject to butchery or some sort of preparation by hominid hands.

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