Doctor of Philosophy

dissertationStable isotope analysis of biological and geological materials has provided important information on environmental change over many timescales. Such records rely on an interpretive framework of large isotopic datasets of recent (i.e., modern and/or Holocene-aged) material in order to define paleoecological interpretations. This dissertation will contribute to a better understanding of ancient and historical ecological change in East Africa by (1) providing a modern interpretive framework for a megaherbivore, Hippopotamus amphibius, in East Africa and (2) investigating the relationship between climate and ecology in Kenya during the Holocene using multiproxy records, including stable isotopes of large mammalian herbivores and leaf wax biomarker isotopes. Although H. amphibius (hippo) tooth enamel isotopes are widely used to understand paleoenvironment, little is known about their dietary variability across time and space. In this dissertation, I present an extensive study on stable isotope serial samples (δ13C and δ18O) of modern hippos in order to understand the breadth of their dietary and behavioral flexibility in Kenya. This large dataset (10 mm interval samples of canine tooth enamel for 30 hippo canines; 1,410 samples in total) reveals the remarkable dietary diversity of hippos: they are indiscriminate feeders and can consume both C3 and C4 herbaceous forage. Furthermore, certain profiles with known death dates have captured isotopic indicators of ecological perturbations, such as drought and C3 plant encroachment following elephant extirpation. Multiproxy records of ecology can provide even more paleoecological information than single-mammal records. Assumptions about environmental change in the fossil record are often based on inference from known global climate and presumed changes in ecology. Using a multiproxy approach (tooth enamel isotopes and leaf wax biomarkers), I present Holocene (11.8 Kya - present) paleoecological data from two basins: the arid Turkana Basin in northern Kenya and the more mesic Victoria Basin in southwestern Kenya. These data indicate that as the monsoon was weakening due to global climatic change (i.e, Milankovitch forcing), there was an increase in C3 resources (bush, shrub, trees, and herbs) in Turkana, whereas Lake Victoria remained predominately C4 (tropical lowland grasses). This interbasinal record reveals that we cannot make assumptions about changes in ecology in an entire region based on climatological forcing mechanisms alone

Presenting the AfriArch Isotopic Database

AfriArch is an archaeological and paleoenvironmental data community designed to integrate datasets related to human-environmental interactions in Holocene Africa. Here we present a dataset of bioarchaeological stable isotope (C/N/O) and radiocarbon measurements from African archaeological sites spanning the Holocene. Modern measurements, when reported together with archaeological data in original publications, are also included. The dataset consists of 5568 entries and covers the entirety of Africa, though most isotopic research has been concentrated in southern Africa. The AfriArch isotopic dataset can be used in paleodietary, paleodemography, paleoclimatic, and paleoenvironmental studies. It can also be employed to highlight data gaps across space and time and set future research agendas

Detecting intraannual dietary variability in wild mountain gorillas by stable isotope analysis of feces

We use stable isotope ratios in feces of wild mountain gorillas (Gorilla beringei) to test the hypothesis that diet shifts within a single year, as measured by dry mass intake, can be recovered. Isotopic separation of staple foods indicates that intraannual changes in the isotopic composition of feces reflect shifts in diet. Fruits are isotopically distinct compared with other staple foods, and peaks in fecal δ 13 C values are interpreted as periods of increased fruit feeding. Bayesian mixing model results demonstrate that, although the timing of these diet shifts match observational data, the modeled increase in proportional fruit feeding does not capture the full shift. Variation in the isotopic and nutritional composition of gorilla foods is largely independent, highlighting the difficulty for estimating nutritional intake with stable isotopes. Our results demonstrate the potential value of fecal sampling for quantifying short-term, intraindividual dietary variability in primates and other animals with high temporal resolution even when the diet is composed of C 3 plants. C3 photosynthesis | feeding ecology | great apes | Ugand

Diet and evaporation sensitivity in African ungulates: A comment on Faith (2018)

International audienc

Palaeobiology of an extinct Ice Age mammal: stable isotope and cementum analysis of giant deer teeth

The extinct giant deer, Megaloceros giganteus, is among the largest and most famous of the cervids. Megaloceros remains have been uncovered across Europe and western Asia, but the highest concentrations come from Irish bogs and caves. Although Megaloceros has enjoyed a great deal of attention over the centuries, paleobiological study has focused on morphometric and distributional work until now. This paper presents quantitative data that have implications for understanding its sudden extirpation in western Europe during a period of global climate change approximately 10,600 14C years ago (ca. 12,500 calendar years BP). We report here the first stable isotope analysis of giant deer teeth, which we combine with dental cementum accretion in order to document age, diet and life-history seasonality from birth until death. Enamel ?13C and ?18O measured in the second and third molars from seven individual giant deer suggest a grass and forb-based diet supplemented with browse in a deteriorating, possibly water-stressed, environment, and a season of birth around spring/early summer. Cementum data indicate that the ages of the specimens ranged from 6.5 to 14 years and that they possessed mature antlers by autumn, similar to extant cervids. In addition, the possibility for combining these two techniques in future mammalian paleoecological studies is considered. The data presented in this study imply that Megaloceros would have indeed been vulnerable to extirpation during the terminal Pleistocene in Ireland, and this information is relevant to understanding the broader pattern of its extinctio

Aridity and early hominin environments

International audienc

Aridity and early hominin environments

International audienc

Aridity and early hominin environments

International audienc

Paleoenvironmental context of the Middle Stone Age record from Karungu, Lake Victoria Basin, Kenya, and its implications for human and faunal dispersals in East Africa

The opening and closing of the equatorial East African forest belt during the Quaternary is thought to have influenced the biogeographic histories of early modern humans and fauna, although precise details are scarce due to a lack of archaeological and paleontological records associated with paleoenvironmental data. With this in mind, we provide a description and paleoenvironmental reconstruction of the Late Pleistocene Middle Stone Age (MSA) artifact- and fossil-bearing sediments from Karungu, located along the shores of Lake Victoria in western Kenya. Artifacts recovered from surveys and controlled excavations are typologically MSA and include points, blades, and Levallois flakes and cores, as well as obsidian flakes similar in geochemical composition to documented sources near Lake Naivasha (250km east). A combination of sedimentological, paleontological, and stable isotopic evidence indicates a semi-arid environment characterized by seasonal precipitation and the dominance of C grasslands, likely associated with a substantial reduction in Lake Victoria. The well-preserved fossil assemblage indicates that these conditions are associated with the convergence of historically allopatric ungulates from north and south of the equator, in agreement with predictions from genetic observations. Analysis of the East African MSA record reveals previously unrecognized north-south variation in assemblage composition that is consistent with episodes of population fragmentation during phases of limited dispersal potential. The grassland-associated MSA assemblages from Karungu and nearby Rusinga Island are characterized by a combination of artifact types that is more typical of northern sites. This may reflect the dispersal of behavioral repertoires-and perhaps human populations-during a paleoenvironmental phase dominated by grasslands