Saharan herders and hunters spread southward to the Sahel, reaching eastern Africa by 4.5 k.a. cal BP. The earliest pastoralists entered southern Kenya through the Great Rift Valley by 3,2 k.a. cal BP, having migrated southward from the Lake Turkana region where they had arrived ca 4 k.a. cal BP. They eventually reached southern Africa with sheep and cattle around 2 k.a. cal BP.
Exploratory lithic analysis in southern Kenya has identified numerous stylistic attributes that differentiate two distinct Pastoral Neolithic (PN) groups from one another, and from the hunter-gatherers who occupied the region during a time period of roughly 2000 years, approximately between 3,2 and 1,2 k.a. cal BP. These early migrants relied on herds that include African cattle, goats, sheep introduced through the Nile corridor, and donkeys. There is no evidence of plant cultivation or agriculture being practiced in southern Kenya during the PN.
These entities associated with domesticated fauna co-occupied a large territory for almost 2 k.a and yet maintained rigid differences in material culture, ceramic styles and burial practices. Geo-chemical sourcing analyses have added an additional dimension to these differences, showing that the “Elmenteitan” and “Savanna Pastoral Neolithic” (SPN) groups obtained obsidian for tool production from two discrete sources in the Great Rift Valley.
For both SPN and Elmenteitan producing groups, Obsidian was the dominant source of lithic raw material for tool production, although there was occasional use of lower quality alternatives. SPN groups were linked together through their reliance on a small cluster of grey obsidian sources in the Lake Naivasha (picture below) basin while Elmenteitan sites are sourced to a discrete outcrop of green obsidian on the northeast slope of Mt. Eburru, only 10 km north of the SPN source.These sources do not appear to have been exploited by foraging groups before and the patterns of SPN and Elmenteitan source preference are maintained within a 250 km radius from the Rift Valley sources.
Qualitative differences in lithic typology and technology exist, and provide a means of distinguishing between Elmenteitan and SPN assemblages. Elmenteitan blades are longer and less curved than those of the SPN, and are more likely to be notched /strangled and retain evidence of intensive use.
The close proximity of these sources to each other, but long distance from the dense pastoral occupations to the southwest has stimulated discussion on social institutions and exchange networks during the Pastoral Neolithic. These discussions are largely structured around the assumptions that people acquired obsidian primarily through exchange network and that transport costs increased with distance from the sources, leading to more intensive reduction of obsidian tools at distant habitation sites. This hypothesis has falsified recently: The reduction pattern and intensity of obsidian scrapers clearly indicates that communities across a large landscape had regular and consistent access to obsidians from distant sources.
How this pattern can be contextualized within a technological organization framework and what this pattern means for the co-occupation of the same areas by a least two distinct groups remains an open question..