The site of Kanjera occurs on the Homa Peninsula of western Kenya. It’s located in the beautiful rural countryside, surrounded by eroded volcanic edifices, on the southern shore of the Winam Gulf of Lake Victoria. Excavations by a Smithsonian – National Museums of Kenya team began in 1987, and have continued under the leadership of Dr. Tom Plummer, who is now chairman of the Anthropology Department at Queens College, City University of New York. Tom’s most recent excavations have focused on Kanjera South, where he, Rick Potts of the Smithsonian, and other members of the team have discovered the oldest archeological evidence of early human activities in a grassland environment, dating to 2 million years ago.
The time between 3.0 and 1.5 million years ago was a critical period in human evolution. Events such as the evolution of the genus Homo, the origin of stone technology, the first evidence of large mammal butchery, elongation of the legs, and adaptations to hot, dry environments took place during this time. It’s been speculated that these major innovations were linked to the spread of grassland ecosystems in Africa. Although the analysis of deep-sea drill cores shows that a shift to a cooler, drier, and more variable global climate did occur during this period, evidence for grassland ecosystems, and for early human activities in these grasslands, has been lacking. Previous discoveries have not been able to show with certainty that early humans were actually living in grasslands at this point in human evolution.
Study of the excavated sediments, fossil animal remains, and stone tools included chemical analyses that enable scientists to determine the kinds of plants that occurred in the ancient habitat. The analyses showed that the excavated archeological sites at Kanjera South – which preserve Oldowan tools, the oldest-known type of stone technology – were located in a grassland-dominated ecosystem from the crucial time interval. These findings were reported in the online science journal PLoS ONE (2009).
Other publications by the team show that the Kanjera hominins obtained meat and bone marrow from a variety of animals, and that they carried stone raw materials over surprisingly long distances in this grassland setting. Comparison with other Oldowan sites shows that by 2.0 Ma, hominins, almost certainly of the genus Homo, used a broad spectrum of habitats in East Africa, from open grassland to woodlands. The combined evidence suggests that early Homo was flexible in its habitat use, and that the capacity to find food, water, and other resources in a range of open and wooded settings was a vital aspect of its adaptation. This strongly contrasts with the habitat use of older species of Australopithecus, and appears to signal an important shift in early human use of the landscape.