The Reflection of an Ape an Aquatic Approach to Human Evolution
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The Reflection of an Ape An Aquatic Approach to Human Evolution A thesis submitted to the Miami University Honors Program in partial fulfillment of the requirements for University Honors with Distinction by Erica Kempf December 2006 Oxord, Ohio Acknowledgements There are a number of people I would like to thank for their help in the production of this story. Linda Marchant was my advisor and provided invaluable data, advice, support, and motivation during this venture. Lynn and Greg Kempf offered helpful feedback throughout, but especially during the early stages of writing. Mary Cayton and Scott Suarez kindly agreed to read the last draft of my project, and gave me final grammatical suggestions to further polish my final copy. I am also grateful to the people whose enthusiasm and moral support throughout the long process of writing this story kept me going: Amanda Zorn, Kait Jones, Ali Wolkin, Ashley Piening, Lindsay Good, Rachel Mount and Jamie Eckert. Special thanks also go to Randy Fiedler for the initial idea to begin this work and for his help in getting started. Table of Contents Introduction viii Map x Kinship Chart xi 1 Meer 1 2 Natte 13 3 Bain 18 4 Welle 22 5 Etang 28 6 Praia 34 7 Lago 39 8 Samman 43 9 Rio 47 10 Alga 51 11 Gens 56 Works Consulted 59 Introduction The study of how humans have come to be what we are has fascinated us for as long as we have written such things down, and for countless generations before that through oral histories. Every human culture has some type of creation myth, a tale of how people came to be on Earth, ranging from molded mud to thrown rocks to drops of deity’s blood and nearly everything in between. When human fossils were first discovered, science offered its own explanations, which have been corrected and fine-tuned with each new discovery. Charles Darwin provided a mechanism for change over time, natural selection. Gregor Mendel showed how parents passed on genetic information to their offspring via alleles. James Watson and Francis Crick discovered the structure of DNA. The Leakey family discovered and analyzed early human ancestor fossils in Africa. Jane Goodall spent decades studying the behavior of chimpanzees for clues about what makes us similar to and different from our closest living relatives. All of these people, and many others, have allowed for huge leaps forward in our scientific understanding of how humans have become what we are today, and their contributions are indispensable. However, as they are probably the first to admit, there are still many unanswered questions about the evolution of humankind. DNA analysis provides valuable information about relationships between animals but has a limited ability to predict behavior. Paleontology has provided a wealth of knowledge about our ancestral anatomy, behavior, and environment, but only a limited number of bones fossilize and are discovered. Advances in these fields will continue to uncover new knowledge and lead to a greater understanding of ourselves, but we are not there yet. One of the areas of most uncertainty is the time directly following the split of humans from the last common ancestor between chimpanzees and humans. What was it that made one group of African apes so different from all the others? A variety of explanations have been proposed, but none are accepted as the definitive cause. These theories range from changes in environment to changes in social structure to meat eating, and all have their advantages and drawbacks. In this story, I have chosen one theory, nicknamed the aquatic ape theory, for explaining what may have caused this divergence of humans from the other apes. This aquatic theory is certainly not the only theory of why and how this change could have taken place, and perhaps is not even the most plausible explanation, but it does offer an explanation for several traits unique to humans. The story presented here follows one band of creatures as they progress from the last common ancestor between humans and chimpanzees until they are firmly established as a hominin that walked the plains of Africa, striding on two feet. The time span, nearly five million years, is almost incomprehensible for humans who live such a short time comparatively. To ensure that readers (and the writer) are not overwhelmed by the sheer amount of time in question, the characters of this story will remain the same throughout this vast expanse. The storyline will seem to pass only through one generation in the life of this band, although obviously the same individual band members would not have survived for five million years. Similarly, the snapshots of life presented in each chapter are not meant to represent literal days or weeks, but rather a progression of what could have happened in the several hundred thousand years between each chapter. Sometimes new behaviors are adopted with incredible rapidity, and then long periods of time pass with little change. Sometimes, though, it takes generations for a new behavior to become established and perfected. New ways to do things are often discovered by chance, and the scenarios described in the following pages are only educated guesses about how certain behaviors might have first been established based on modern animal behavior. Ultimately this is a “what if” story. What if the aquatic ape hypothesis were true? What would have driven our ancestors to spend a significant amount of time in the water? How would they have acted while they were there? What made them return exclusively to dry land again? The introduction to each chapter presents scientific data relevant to aspects of each chapter, and the bibliography at the end provides the scientific sources the author used in predicting the band’s behaviors and physical characteristics. These scientific sections are meant to offer support to this hypothesis and resources for curious readers, rather than to offer undisputed proof that any of the following events occurred. Contemporary Map of the Afar Region in Ethiopia Kinship Chart Meer Alga Etang Welle Natte Rio Etang Samman Teich Furt Gens The Reflection of an Ape An Aquatic Approach to Human Evolution A thesis submitted to the Miami University Honors Program in partial fulfillment of the requirements for University Honors with Distinction by Erica Kempf December 2006 Oxord, Ohio Acknowledgements There are a number of people I would like to thank for their help in the production of this story. Linda Marchant was my advisor and provided invaluable data, advice, support, and motivation during this venture. Lynn and Greg Kempf offered helpful feedback throughout, but especially during the early stages of writing. Mary Cayton and Scott Suarez kindly agreed to read the last draft of my project, and gave me final grammatical suggestions to further polish my final copy. I am also grateful to the people whose enthusiasm and moral support throughout the long process of writing this story kept me going: Amanda Zorn, Kait Jones, Ali Wolkin, Ashley Piening, Lindsay Good, Rachel Mount and Jamie Eckert. Special thanks go to Randy Fiedler for the initial idea to begin this work and for his help in getting started. Table of Contents Introduction ii Map iv Kinship Chart v 1 Meer 1 2 Natte 11 3 Bain 19 4 Welle 26 5 Etang 35 6 Praia 44 7 Lago 52 8 Samman 59 9 Rio 66 10 Alga 72 11 Gens 80 Works Consulted 85 1 Danakil Alps (Afar, Ethiopia) 9 Million Years Ago Meer (Sea; German) The Afar region is located in East Africa, along the coast of the Red Sea. Today huge salt plains cover this area. The local people collect and carry out this salt for sale; salt is the only cash crop in this otherwise inhospitable region. The modern day salt plains of Afar are all that is left of a vast inland sea that once covered the region. Around 9 million years ago the three geological rifts that converge in the Afar triangle shifted and the Red Sea flowed into Afar. Later, another shift occurred, blocking the sea’s retreat and turning Afar into a huge saltwater lake. The lake slowly evaporated over millions of years and left thick crusts of salt as its only remnants. A similar process is occurring in the Dead Sea today, which is steadily increasing in salinity as it evaporates. Around the same time in Africa, an ape lineage split. This ape lineage is sometimes referred to as the last common ancestor, or LCA. The modern genera of Pan (chimpanzees) and Homo (humans) are the living descendants of this split. The time estimation for this split is based on our understanding of the molecular clock and the accumulation of mutations in the DNA of the two species since the divergence. An analysis of chimpanzee and human DNA suggests that this event occurred between 7 and 9 million years ago. It is difficult to determine from the array of fossil evidence exactly which fossils belong to the LCA. These fossils may not have yet been discovered or preserved so that they may be discovered at all. However, modern day animals may offer clues as to the nature of these ancestral apes. Deciding which animals make the best model for the LCA is based on a variety of fossil and behavioral data. It is assumed that the LCA more closely resembled Pan than Homo because it is more likely that uniquely human traits such as naked skin, standing upright and large brains evolved after the split between 2 humans and chimpanzees rather than before the split. The alternative explanation would be that the LCA evolved these human traits and then the chimpanzee line evolved back to the ancestral condition, which involves more steps and is refuted by the fossil evidence.