Date of Award

Spring 1-1-2018

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

First Advisor

Matthew J. Sponheimer

Second Advisor

Nico L. Avenant

Third Advisor

Herbert H. Covert

Fourth Advisor

Jaelyn J. Eberle

Fifth Advisor

Joanna E. Lambert

Abstract

Environmental change, especially the expansion of open C4 savanna grasslands at the expense of more heavily wooded C3 habitats, is frequently cited as a driver of hominin evolution. The disappearance of the genus Australopithecus, the rise of the cranio-dentally robust Paranthropus, and the emergence of Homo have all been linked to environmental change during the period from 3 and 2 Ma. The large mammal communities which co-existed with hominins are often used to reconstruct paleoenvironments during this period, but small mammals have been relatively underutilized despite their potential to provide information about hominin ecosystems at a fine scale. A primary goal of this dissertation was to determine whether patterns of evolutionary change observed in the large mammal fossil record of southern Africa during the Plio-Pleistocene are also evident in the small mammal record.

A combination of stable carbon isotope analyses and taxon-dependent analyses were deployed, and in some cases significantly developed, in re-assessing the micromammalian fossil record associated with early hominins. Large gaps remain in our knowledge of small mammal isotopic ecology, especially in African ecosystems, where C4 plants are abundant and many landscapes relevant to hominin evolution persist. This dissertation focuses, in part, on understanding the relationship between small mammal stable carbon isotope composition and their habitats in a modern southern African C4 savanna and applying this information to the fossil record. It was determined that small mammal δ13C compositions record habitat composition. However, insectivores appear to track proportions of C3/C4 vegetation better than rodents. Preliminary analyses of the δ13C composition of fossil tooth enamel of small mammals from early hominin-bearing deposits in southern Africa suggest that C4 resources may have been more abundant in the past.

Taxonomic-dependent faunal analyses indicate no clear shift from more mesic, closed habitats to more open-grassy habitats between 3 and 1 Ma in southern Africa, but instead suggest that the environment in this region was predominantly open with patches of mesic C3 woodland habitat. Australopithecus africanus and Paranthropus robustus appear to have been associated with both habitat types, perhaps taking advantage of resource-rich C3 habitat patches whenever they were available.

Share

COinS