Hominin Ecology of the Early Oldowan 2 Ma

Abstract

Environmental change is key for human evolution, especially at times of anatomical and behavioral change in life histories, such as the origin of meat consumption, economic diversification, and dispersal. However, for the earliest phase of human evolution featuring the technology-dependent hominins that shaped our lineage since 2.6 Ma, the Oldowan, there is a dearth of archaeological evidence directly associated with rich chronostratigraphic and environmental datasets amenable to tracking ecological change and adaptation to new physiographic conditions. One place where this type of information has been recently retrieved is the Western Plio-Pleistocene rift basin of Olduvai Gorge (now Oldupai), Tanzania. We explore habitat range by Oldowan-bearing hominins amidst extremely diverse ecosystems throughout a stratified sequence 235 ka-long, thus predating by >180 ka the earliest landmark fossil hominins and classic Oldowan from the Eastern side of the basin. Our study provides multi-proxy evidence of environmental adaptability, demonstrating colonisation of fresh volcanic landscapes and occupation of fast-changing biomes by 2 Ma.

Sourcing Oldowan and Acheulean Stone Tools in Eastern Africa

“…Recent excavations revealed that hominins produced cores, spheroids, flakes, and retouched pieces on quartzite, ignimbrite, gneiss, and basalt (Mercader et al 2021). ED-XRF analyses of quartzite lithics indicated that hominins procured stone from at least three primary sources, two of which were located ~12 kilometres to the east, while other raw materials were likely provisioned from nearby stream channels (Mercader et al 2021). The next oldest site in the study area is known as…”

“…The study area's earliest known archaeological site is Ewass Oldupa (~2.04-1.82 Ma) (Table 1; Figure 4), which refers to an outcrop in the western palaeobasin. Recent excavations revealed that hominins produced cores, spheroids, flakes, and retouched pieces on quartzite, ignimbrite, gneiss, and basalt (Mercader et al 2021). ED-XRF analyses of quartzite lithics indicated that hominins procured stone from at least three primary sources, two of which were located ~12 kilometres to the east, while other raw materials were likely provisioned from nearby stream channels (Mercader et al 2021).…”

“…For instance, because ED-XRF spectroscopy measures major oxides in weight % and trace elements in parts per million, concentrations estimates can be rescaled to the range of [0-1] using the Min-Max transformation method (e.g. Mercader et al 2021). Alternatively, geochemical data can be logarithmically transformed to stabilise variance and reweigh variables to approach a normal distribution since many statistical tests follow the assumption of normality (e.g.…”

“…Hay 1976;Kleindienst 1973;Kyara 1999;McHenry & de la Torre 2018;Tactikos 2005). The resultant belief that the local outcrops were largely undifferentiable from one another has since shown to be erroneous evidenced by recent characterisation studies complimented by archaeological testing (Egeland et al 2019;Favreau et al 2020;Mercader et al 2021;Soto et al 2020aSoto et al , 2020b. Aside from quartzite, the dynamic geological history of Eastern Africa led to the petrogenesis of various igneous, metamorphic, and sedimentary rock types (Cahen et al 1984), which have only recently begun to be comprehensively studied within the framework of archaeological research but have already offered revelatory insights into early hominin stone transport (Braun et al 2008).…”