Climate Variability and the Early Stone Age – Middle Stone Age Transition in East-Central Africa


MICHAEL BISSON

DEPARTMENT OF ANTHROPOLOGY AT McGILL UNIVERSITY


Anatomically modern Homo sapiens (AMHs) evolved as a continent wide phenomenon in
Africa roughly 300,000 years ago, within the time span (~ 500,000 to 250,000 years ago) of the
technological transition from the Early Stone Age (ESA) to the Middle Stone Age (MSA). The
ESA-MSA transition in Africa is complex and poorly understood in part due to dating problems,
the rarity of intact stratified sites, and imprecise and outdated definitions of the archaeological
materials. Recently, it has become an important topic because many technological signs of
complex cognition appear first in the late ESA or early MSA. Spatial and temporal
environmental variability induced by climate change is thought to have driven hominins physical
and cultural evolution, as well as stimulating or inhibiting hominin dispersals. Zambia in south-
central Africa has produced some of the earliest dates for both the MSA and complex cognition
(hafted tools, pigment use) in Africa and has one of the only dated stratified sites (Kalambo
Falls) that include both the final ESA “Acheulean” and the initial MSA “Sangoan” technological
traditions. Our goal is to amplify our understanding of this key region by modeling late Middle
and Upper Pleistocene climate and vegetation with the help of both global and local proxies as
well as investigating a recently discovered locality in northeastern Zambia with abundant early
MSA sites including some that may bridge the ESA-MSA transition. We will employ modern
analytical methods to describe the ESA and early MSA assemblages; date them using advances
in optically stimulated luminescence and uranium series techniques; use geoarchaeological and
regional climate reconstructions to situate them in their correct ecological context, and
technological and micro-wear analysis to determine the activities carried out by the stone tools.
Recently published sediment cores from Lake Malawi, only 130 km from our research area,
provide a detailed local record of rainfall variation over the past 1.3 million years that will aid
our environmental reconstructions of the region as a whole. This record indicates dramatic and
sometimes rapid rainfall fluctuations during the period from ca. 500,000 to 250,000 years ago
that would create precisely the diachronic environmental heterogeneity that could initiate
hominin speciation and dispersals in this part of Africa.