The 81st Annual Meeting of the American Association of Physical Anthropologists (2012)


Integrating ecological proxies to understand the distribution of woody plants in African environments

AMY L. RECTOR1,2, KAYE E. REED2 and CHRISTOPHER J. CAMPISANO2.

1School of World Studies, Virginia Commonwealth University, 2Institute of Human Origins and School of Human Evolution and Social Change, Arizona State University

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Recently, Cerling and colleagues (2011) reinterpreted soil carbon isotopes from East African hominin localities, concluding that woody cover in the earliest hominin habitats was less than previously suggested. They note that from ~3.6 – 3.0 Ma, woody cover increased to 40 – 60%; a value corresponding to fairly closed habitats – unless the woody cover is shrubs. There appears to be a key disjunction between type and amount of woody cover represented by soil isotopes and paleohabitat reconstructions using associated mammalian fauna from some hominin localities.

To explore this disjunct, we analyzed the large mammal communities from 52 modern African sites using correspondence analyses to determine the relationship between community membership and vegetation structure. We included more than 20 modern communities that corresponded to Cerling et al.’s soil isotope collection areas. Sites were coded according to UNESCO habitat designation, and were analyzed using mammalian trophic and substrate adaptations that are known to reflect vegetation structure ranging from forests through grasslands. Results suggest that mammalian community structures do not correspond to woody cover suggested by the soil isotopes, possibly because of the inability of the isotope data to distinguish among trees, bushes or shrubs. Conversely, ecological community structure can predict mean annual precipitation, which is associated with type of vertical vegetation. We conclude that integrating a variety of methods is necessary for paleoenvironment reconstruction and to understand the interrelationship between the primary evidence provided by photosynthetic pathways and secondary evidence derived from mammals that utilized both the plants and their structure.

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