Western Michigan University ScholarWorks at WMU Master's Theses Graduate College 4-1979 The Origins and Functional Significance of Incest vA oidance R. Daniel Murray Follow this and additional works at: https://scholarworks.wmich.edu/masters_theses Part of the Social and Cultural Anthropology Commons Recommended Citation Murray, R. Daniel, "The Origins and Functional Significance of Incest vA oidance" (1979). Master's Theses. 2044. https://scholarworks.wmich.edu/masters_theses/2044 This Masters Thesis-Open Access is brought to you for free and open access by the Graduate College at ScholarWorks at WMU. It has been accepted for inclusion in Master's Theses by an authorized administrator of ScholarWorks at WMU. For more information, please contact [email protected]. THE ORIGINS AND FUNCTIONAL SIGNIFICANCE OF INCEST AVOIDANCE by R. Daniel Murray A Thesis Submitted to the Faculty of The Graduate College in partial fulfillment of the Degree of Master of Arts Western Michigan University Kalamazoo, Michigan April 1979 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. ACKNOWLEDGEMENTS This thesis is a product of a long-term interest in the stud}7 of human and non-human primate ethology. Initially I would like to thank Robert P. Collins, Department of Biology, St. Clair County Community College, for the enthusiastic introduction to the fields of anthropo­ logy and primatology he provided early in my undergraduate career. During my graduate training, I have gained from the advice and encour­ agement of my major professor, Dr. Robert Jack Smith, as well as the entire faculty of the Department of Anthropology at Western Michigan University. The gratitude extended to those mentioned does not diminish my full responsibility for the contents of this thesis. R. Daniel Murray Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. INFORMATION TO USERS This was produced from a copy of a document sent to us for microfilming. While the most advanced technological means to photograph and reproduce this document have been used, the quality is heavily dependent upon the quality of the material submitted. The following explanation of techniques is provided to help you understand markings or notations which may appear on this reproduction. 1. The sign or “target” for pages apparently lacking from the document photographed is “Missing Page(s)”. If it was possible to obtain the missing page(s) or section, they are spliced into the film along with adjacent pages. This may have necessitated cutting through an image and duplicating adjacent pages to assure you of complete continuity. 2. 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Requests can be made to our Dissertations Customer Services Department. 5. Some pages in any document may have indistinct print. In all cases we have filmed the best available copy. Uni International 300 N ZEEB ROAD. ANN ARBOR. Ml 48106 18 BEDFORD ROW. LONDON WC1R 4EJ. ENGLAND Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 1312980 MURRAY, R. DANIEL THE ORIGINS AND FUNCTIONAL SIGNIFICANCE OF INCEST AVOIDANCE. WESTERN MICHIGAN UNIVERSITY, H.A., 1979 University Microfilms International 3 0 0n ztee road, ann arbor, mi 48io6 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. i i i TABLE OF CONTENTS CHAPTER PAGE I INTRODUCTION ................................... 1 II THEORETICAL BACKGROUND ......................... 3 Sociocultural Explanations of Incest Avoidance and Exogamy ..................... 5 Previous Biological Thought on the Origins of Outbreeding ........................... 7 III EVIDENCE FOR A BIOLOGICAL BASIS OF INCEST AVOIDANCE .................................. 12 Aversions to Incestuous Pairing in Primates and Other Mammals......................... 12 Recent Support for the Westermarck H y p o t h e s i s .............................. 17 IV THE GENETIC ADVANTAGES OF O U T B R E E D I N G .......... 24 Deleterious Recessives: A Cause or a Result of the Outbreeding Pattern ......... 25 The Selective Advantages of Variability.............................. 29 Problems of Small-Population Genetic D r i f t .................................... 31 Outbreeding, Heterosis and Evolution ......... 34 V CONCLUSIONS ................................... 39 VI REFERENCES CITED ............................... 41 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. INTRODUCTION The prohibition of incest, whether characterized by avoidance behavior in non-humans or a cultural manifestation as taboo in human groups, has recently occupied a considerable portion of the ethologi- cal and anthropological literature. Following Fox (1972) and Parker (1976), the incest taboo is regarded as strictly a cultural prohibi­ tion of mating between specific members of the consanguineous group, while incest avoidance refers to the more basic mammalian behavioral tendency to avoid mating with siblings, parents, and offspring. The ethnographic literature covering a multitude of cultures leads us to conclude that the presence of an incest taboo is probably uni­ versal in all human groups, although it is manifested in a variety of ways in which precise mechanisms and functions appear at this time to be elusive. If we are to understand fully the functional relationships of any particular incest prohibition or its culturological implications, we may first find it useful to assess the possible causal mechanisms for the general pattern of incest avoidance among the social mammals, with special attention to the order of primates. Despite a strong tendency to relegate genetic influence to any behavior that consistently transcends taxonomic boundaries, very little attention has been devoted to those genetic and psychobiological in­ fluences that may underlie the inclination to outbreed. With the recent documentation of non-human primate incest avoidance (Sade, 1968; Tokuda, 1961-1962; Enomoto, 1978; van Lawick Goodall, 1968; Harcourt, Stewart, and Fossey, 1976), kin selection theory (Hamilton, 1963; 1964; 1 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 2 Maynard Smith, 1964), and beneficial results of heterosis as a result of outbreeding (Schrieder, 1978), it seems appropriate to return to these issues to readdress the possible selective advantages of this mammalian trait. The purpose of this essay is to present an alternative functional explanation for the origins of incest avoidance, specifically suggesting a superimposition of human culture upon a biological substrate. For heuristic purposes, special emphasis is placed upon the general incest avoidance patterns among all primates and the interrelationship between socialization and subsequent aversion to consanguineous sexual bonding. Incest avoidance is viewed as an expression of the genome providing a predisposition to avoid sexual contact with those with whom the indi­ vidual was socialized. Individual, rather than group genetic fitness is emphasized in the discussion of the ontogeny of this pattern. The existing neuro-physiological mechanisms of this sexual indifference toward kin will be mentioned briefly, but are considered peripheral to the primary genetic functional considerations. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. THEORETICAL BACKGROUND The problem of delineating the relative contributions of culture and biology to human behavior has suffered a long history of little reward in the social sciences. Indeed, many anthropologists, including Kroeber and White, have attempted to separate the two, considering culture a thing sui generis. As Parker (1976) has pointed out, the reluctance to attribute a biological influence to human behavior may be founded in fear of "rejection of sociocultural causation" (1976:286). More importantly, the culture-biology distinction may stem from the anthropocentric tendencies that dogmatically view a sharp distinction between animal and human behavior - the latter to be attributed solely to environment and learned behavior (culture), while the former is relegated to a combination of social and bio-genetic forces (van den Berghe, 1974). The more recent use of sociobiology (Wilson, 1975; Barash, 1977) to explain some human behavioral patterns has likewise met with consid­ erable criticisms within the field of anthropology. For Sahlins, Sociobiology challenges the integrity of culture as a thing-in-itself, as a distinctive