Using Primate Comparative Biology to Understand Human Uniqueness

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A fundamental question in biology concerns the ways that species differ from one another. Perhaps nowhere is this more prominent than in the field of biological anthropology, where researchers investigate how and why humans differ from other primates, often under the assumption that human traits resulted from a unique constellation of forces that made our lineage particularly successful. Humans are clearly unique in many ways relative to other primates, including use of language, impressive problem-solving abilities, and cumulative cultural evolution. It is less clear how other biological traits - such as life history and physiology - have catalyzed these major changes. Have our unique cognitive abilities arisen from only a few underlying biological changes, or many changes? Which traits are involved, and how do they relate to one another? The central goal of this research to rigorously identify biological traits that are exceptional in humans, and thus important to other traits involved in our extraordinary success. This goal will be achieved through in-depth, advanced analyses of a wide range of important variables involving brain size, lifespan and related traits, and key physiological variables, such as immune system characteristics and body temperature. The research team will also investigate parasites and pathogens, which have been hypothesized to be super-abundant in humans, yet are known to depress cognitive performance. Two new statistical approaches will be developed. One set of methods predicts trait values in humans based on a statistical model estimated in non-human primates, and then evaluates whether the observed value in Homo sapiens departs from the predicted value. A second set of methods investigates evolutionary rates on different parts of an evolutionary tree. Under the hypothesis that a biological trait is exceptional in humans relative to non-human primates, elevated rates of evolutionary change in that trait are expected along the lineage leading to humans. In terms of intellectual merit, the research will open new avenues to better integrate studies of non-human primates into our understanding of human evolution. In the process, the research will address the question, what are the fundamental biological traits that have lead to human uniqueness and success? The new methods complement existing approaches to studying the fossil record, and they provide ways to investigate traits that do not fossilize, including behavioral and ecological traits. The research also will support important broader impacts, especially involving hands-on training in statistics and databases for the next generation of young scientists, and opportunities for these developing scientists to expand their knowledge of biology and anthropology. The research team also will produce new databases of primate and human characteristics that enable other scientists and students to investigate additional research questions important in the fields of biological anthropology. Finally, the investigator will organize a conference symposium in the final year of funding to share the results of this effort and stimulate future extensions of it