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1 Pan-African Climate Variability Since the Plio Pan-African Climate Variability since the Plio-Pleistocene and Possible Implications for Hominin Evolution Item Type text; Electronic Dissertation Authors Billingsley, Anne Louise Publisher The University of Arizona. Rights Copyright © is held by the author. Digital access to this material is made possible by the University Libraries, University of Arizona. Further transmission, reproduction, presentation (such as public display or performance) of protected items is prohibited except with permission of the author. Download date 01/10/2021 17:15:21 Link to Item http://hdl.handle.net/10150/634339 1 PAN-AFRICAN CLIMATE VARIABILITY SINCE THE PLIO-PLEISTOCENE AND POSSIBLE IMPLICATIONS FOR HOMININ EVOLUTION By Anne Louise Billingsley __________________________ Copyright © Anne Louise Billingsley 2019 A Dissertation Submitted to the Faculty of the DEPARTMENT OF GEOSCIENCES In Partial Fulfillment of the Requirements For the Degree of DOCTOR OF PHILOSOPHY In the Graduate College THE UNIVERSITY OF ARIZONA 2019 2 3 ACKNOWLEDGEMENTS I would like to express my gratitude for my family and friends who inspire and encourage me no matter what crazy decisions I decide to make. In particular, my mother, Mary, and my sister, Mary Lynn. I would like to express how thankful I am for my husband, Andrew Cunningham, who I met while working on this dissertation, and who actually enjoyed my company enough to want to spend the rest of his life with me in spite of the fact that I was working on this dissertation. To all my friends who have been on this journey with me from the beginning when we were just baby geologists, meeting you all and growing as scholars together has been the best part about this experience. My collaborators and labmates: Chad Yost, Jordan Bright, Benjamin Mohler, Kevin Ortiz, Mathew Fox, Jennifer Kielhofer, Kayla Worthey, Brendan Fenerty, Zachary Naiman, David Dettman, Jessie Pearl, Nate Rabideaux, Jeffery Stone, Karlyn Westover, Jose Joordens, Christopher Campisano and the entirety of the HSPDP team. It was a real joy to work with such great people. My committee members have been ever so helpful with advice and guidance: Andrew S. Cohen, Jay Quade, Peter N. Reinthal, Matt Grove and Kevin Anchukaitis. The National Science Foundation (EAR1123000, EAR1338553, BCS124185) and the International Continental Drilling Program provided support for this research. 4 DEDICATION This manuscript is dedicated to my father, Thad Hoffman Billingsley, who inspired my love of the sciences and instilled in me the value of an education. 5 TABLE OF CONTENTS ABSTRACT………………………………………………………………………………………7 INTRODUCTION ………………………………………………………………………………..8 PRESENT STUDY ……………………………………………………………………………...15 REFERENCES ………………………………………………………………………………….22 APPENDIX A: δ13C RECORDS FROM FISH FOSSILS AS PALEO-INDICATORS OF ECOSYSTEM RESPONSE TO LAKE LEVELS IN THE PLIO-PLEISTOCENE LAKES OF TUGEN HILLS, KENYA ……………………………………………………………………….27 Key Points ….……………………………………...…………………………………….28 Abstract ……………………………………………………………………………….…28 1. Introduction……………………………...………………..………………………….29 2. Methods …………………………………..…………………………………….……34 3. Results ……………………………..………………………….……………………..36 4. Discussion ……………………………..…………………….……………………....38 5. Conclusions ………………………..……………...…………………………………40 Acknowledgements ……………….……………………………………………………...41 References ……………………………………………………………………………….41 Figures …………………………………………………………………………………..47 Tables……………………………………………………………………………….……54 APPENDIX B: ORBITAL AND HIGH-LATITUDE CONTROLS OF PLIO-PLEISTOCENE CLIMATE VARIABLITY IN AFRICA, IMPLICATIONS FOR EARLY HOMININS AND THE RISE OF THE GENUS HOMO …………………………………………………………...56 Key Points ……………………………………………………………………………….57 Abstract ………………………………………………………………………………….57 1. Introduction …..…………………...…………………………………………………58 2. Methods ..…………………………………………………………………………….61 3. Results ……..………………………………………………………………………...64 4. Discussion ..………………………………………………………………………….66 5. Conclusions ………..………………………………………………………………...75 Acknowledgements ………………………………………………………………………77 References ……………………………………………………………………………….77 Figures …………………………………………………………………………………..95 6 TABLE OF CONTENTS – Continued APPENDIX C: NEW APPROACHES TO QUANTIFYING PALEOENVIRONMENTAL VARIABILITY AND APPLICATION TO UNDERSTANDING THE EVOLUTION AND DISPERSAL OF ANATOMICALLY MODERN HUMANS OVER THE PAST 400 KA …....99 Key Points ……………………………………………………………………………...100 Abstract ………………………………………………………………………………...100 1. Introduction ………..……………………………………………………………….101 2. Methods ……..……………………………………………………………………...109 3. Results …………………………..………………………………………………….113 4. Discussion ………………………………………..………………………………...115 5. Conclusions …………………………………..…………………………………….129 Acknowledgements ……………………………………………………………………..130 References ……………………………………………………………………………...131 Figures …………………………………………………………………………………145 Tables …………………………………………………………………………………..153 7 ABSTRACT Three studies were performed in order to ascertain how climate variability in Africa may have influenced the speciation, extinction and dispersals of our early hominin ancestors since the Plio-Pleistocene. δ13C values from fish fossils from a Hominin Sites and Paleolakes Drilling Project Core (HSPDP) from Tugen Hills, Kenya were used to determine that local responses to climate shifts between 3.29 – 2.57 Ma were abrupt enough to limit the habitats of fish in the paleolake. Singular spectral analysis and correlation analysis on five paleoenvironmental records from Africa and one from NE Russia indicate that orbital parameters can explain most of the variance in climate records and that there are far reaching high-latitude teleconnections to African climate. An evolutionary algorithm run on reconstructed time-series from western, eastern and southern Africa allowed for environmental context of hominin evolutionary events to be made. Comparisons between the evolutionary model and the paleoanthropological record showed that during a period of relative stability in eastern Africa, 2.9 – 2.7 Ma, a drastic change in environment at 2.8 Ma would have elicited a response from a population of increased plasticity. This event coincides with a major turnover in the faunal assemblages as well as the first appearance of the genus Homo. New methods were developed in order to aggregate and compare paleorecords of different type and thereby quantify periods of high and low climate variability. Both the Standard Deviation Variability Method and the Accumulated Weighted Rate of Change Variability Method proved valuable in determining environmental variability in and around Africa over the last 400-ka. When the new methods were applied to environmental records and compared to the genetic, archaeological and fossil record, they indicated that the earliest appearance of the MSA occurred during a period of high variability in northern and eastern Africa. Furthermore, these methods showed that migrations within and out of Africa 8 occurred after the source region switched from a period of high variability to a stable environment. INTRODUCTION The questions of if and how environment and climate shaped the process of hominin evolution have been hotly debated over the course of the last century. Many hypotheses have been put forth to explain the environmental forcing factors which could have given rise to the features that define the hominin lineage such as increased brain size, bipedalism and the use of tool technologies. Two of the leading hypotheses focus on the increased climate variability early hominins would have experienced. The variability selection hypothesis claims that a continuously changing environment would have selected for early hominins to evolve adaptive strategies, and the accumulated plasticity hypothesis adds to this by suggesting that species experiencing increased climate variability would have evolved phenotypic plasticity, a suite of characteristics and technology which allows for adaptation to a consistently changing environment. During periods of climate stability, these species might be outcompeted by species more adapted to one particular environmental regime (Potts, 1996, 1998; Grove, 2011, 2012, 2014, 2015). In this case, the species with accumulated plasticity would be able to disperse into other regions where they would be able to survive in a variety of novel environments (Grove, 2015). Relating climate variability to human evolution has been difficult because of the lack of environmental records that are at the temporal and spatial resolution needed to make direct comparisons to known evolutionary milestones such as speciation, extinctions and dispersal events. The problem becomes further complicated as there are no direct measures of what constitutes a more variable environment, how different environments will react to various global 9 forcing mechanisms or exactly what sort of amplitude or temporal change in climate is required to elicit an evolutionary response in species. The purpose of the three studies appended to this manuscript is to address some of these concerns. The Plio-Pleistocene is a period of major global climate reorganization as the earth moved from the warm Pliocene into the much colder, more variable Pleistocene at the onset of Northern Hemisphere glaciation. Records from deep sea drill cores as well as multiple terrestrial records indicate that during this period, the African continent became much more arid and climate became increasingly unstable, with fluctuations between wet/dry phases (deMenocal, 1995; Deino et al., 2006; Kingston, 2007; Kingston et al., 2007; Maslin and Trauth, 2009; Trauth et al., 2009).
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