Human Ethology Bulletin

Volume 27, Number 3 ISSN 2224-4476 October 2012 14 Human Ethology Bulletin © 2011 − The International Society for Human Ethology – www.ISHE.org The Evolution of Personality and Individual Differences Book Review John Scott Price Hackmans, Plumpton Lane, Plumpton, East Sussex, UK The Evolution of Personality and Individual Differences, edited by David M. Buss and Patricia H. Hawley. Oxford University Press, 2011, 498 pp. ISBN 978-0-19-537209-0 (Hardback) Evolutionary psychologists have been and this volume is a testimony that they have attacked from a number of directions. They succeeded in doing so. have been criticised for their modular approach The book confronts two challenging by those who favour a more general form of problems. One is the finding that a significant brain function, for their theories resembling part in the variance of each of the big five “just-so stories” rather than directly testable personality factors shows a large genetic hypotheses, and because their work was felt by component. Since adaptive traits should show some to conflict with certain political views. It directional selection, this should not be the case seems not surprising they kept away from other - variation should be wiped out. The two branches of science that are also subject to contenders for this discrepancy are mutation- prejudice, such as psychiatry. selection (the accumulation of very large This volume represents an adaptive numbers of harmful mutations of small effect) radiation away from the initial approach of and balancing selection, which means either evolutionary psychology, which stressed what that some traits are selected for in some the human mind had in common, and starts to environments, such as crowded versus isolated attack the problem of the ways in which living conditions, or that the trait is subject to individuals differ from each other. The Evolution negative frequency-dependent selection. The of Personality and Individual Differences trespasses latter situation occurs when a trait becomes on the field of behavior genetics, which has more adaptive the rarer it becomes, and an already done a lot of work analysing extreme example is heterozygote advantage in personality variation (as expressed in the which the rare allele is more likely to be paired Maudsley Personality Inventory and the “big with another of the same type to create a five”), and has developed sophisticated heterozygote, whereas when it becomes mathematical techniques for partitioning common it is more likely to be paired with variance in personality traits into genetic, another of the same type to form a harmful environmental, epistatic, gene-environment homozygote (as in pernicious anaemia). The interactional and even more exotic components. same argument applies to traits thought to be Clearly, in order to study differences in affected by many genes, such as handedness, so personality, evolutionary psychologists need to that a left-handed duellist is at an advantage master the existing field of behavior genetics, because he has had more practice fighting right- Human Ethology Bulletin, 27(3), 2012 15 handers than the right-hander has had of are not likely to do well either. In other words, a fighting left-handers. group composed of a mix of leaders and The other problem is the finding that only a followers is likely to outcompete groups of small portion of the variance in almost all traits leaders and groups of followers. Within-group is due to shared family environment – about variety gives efficiency, as David Sloan Wilson five percent. That is, a great part of the variance and E.O. Wilson have pointed out (Wilson and not due to genetics is due to non-shared Wilson, 2007; Wilson, 2012), so that humans are environmental factors. Thus, family similar to the eusocial insects in their divisions environment and the influence of parents play a of labour, and have been almost equally lesser part in determining the personalities of successful (so far). Moreover, a group can offspring than commonly assumed. How could develop a culture which selects leaders who are this be? Some answers are given, for example, devoted to the interests of the group rather than in an excellent chapter by Frank Sulloway about to their own selfish interests, and this process the influence of sibling position (pp. 86-120). can develop much more efficiently under group The problems confronting this new approach selection than under individual selection. concerned with individual differences are very Admittedly, leaders of the modern world are well presented by Geoffrey Miller (pp. 376-399), not conspicuous for their charity to the people and also by the editorial introductions and the they govern, but then they do not know them as chapter by our Editor, Aurelio Figueredo, and individuals in the way that leaders of our his co-authors (pp. 210-242). Genetic problems hunter-gatherer ancestors presumably did. are clearly presented by Matthew Keller (and My second criticism relates to the chapter on colleagues, pp. 280-302), who with Geoffrey psychopathology written by Norwegian Leif Miller wrote a landmark article in Behavioral Kennair (pp. 451-480). Regrettably, he fails to and Brain Sciences (Keller & Miller, 2006). mention one of his compatriots, who not only Marco Del Guidice and Jay Belsky contribute a was the first to describe the peck-order in social very readable chapter on life history theory (pp. groups, but also was the first to report 154-176). differences in personality between chickens in I have two main criticisms about the book, the same flock, and described in chickens what and these are problems of omission rather than represent episodes of both major depression commission. The first one relates to the absence and neurotic personality: Thorleif Schjelderup- of any mention of selection at the group level. Ebbe, whose academic aspirations were crushed Group selection can explain a lot of genetic (and by those above him in his own Oslo peck-order. environmental) variance in personality traits. As a lonely boy on his parents’ farm in the Take, for instance, the difference between summer holidays before the first world war, leaders and followers. We all know (albeit by Schjelderup-Ebbe got to know his family's folk psychology) that there are born leaders and chickens individually, and realised that the born followers, and others who can adapt to chickens recognised each other, too. He noted either role depending on circumstances. The that for any given chicken, there were some that characteristic of leadership potential can be it would peck without compunction, and others maintained by negative frequency-dependent which it would peck only at the expense of selection within the group, since a born leader severe retaliation. Also, he noted that if chicken is likely to do better in a group which has no A could peck chicken B, and B were allowed to other born leaders and a follower is likely to do peck C, A too could peck C. I will quote this better in a group in which followers are rare. work at some length, because it seems rarely But this variation maintained by within-group known but is relevant to the subject of this selection is likely to be greatly magnified by volume. Patricia Hawley (p. 67) mentions selection between groups. Groups composed Schjelderup-Ebbe's German 1922 paper entirely of leaders are not likely to be functional (Schjelderup-Ebbe, 1922), but there is no whereas groups composed entirely of followers reference to the description of his findings in Human Ethology Bulletin, 27(3), 2012 16 English (which came many years later, References Schjelderup-Ebbe, 1935). Schjelderup-Ebbe described a difference in countenance between Appleby, M.C. (1983) The probability of high-ranking and low-ranking birds. While the linearity in hierarchies. Animal Behaviour, 31: face of the superior bird “[radiates] with the joy 600-608. of satisfied pecking-lust”, the subordinate has Keller, M.C. & Miller, G. (2006) Resolving “a much less enjoyable and anxious existence” the paradox of common, harmful, heritable (Schjelderup-Ebbe, 1935, p.951), and if trying to mental disorders: Which evolutionary genetic revolt against the despot, the subordinate models work best? Behavioral & Brain Sciences, “fights with less display of energy than usual. It 29: 385-452. seems as if the spirit of the bird were dulled by Schjelderup-Ebbe, T. (1922) Beitraege zur a premonition of hopelessness” (Schjelderup- Sozialpsychologie des Haushuhns. Zeitschrift Ebbe, 1935, p.955). fuer Psychologie, 88: 225-252. In the translation of his 1922 paper, Schjelderup-Ebbe, T. (1935) Social behaviour of Schjelderup-Ebbe (1975) commented that “hens birds. In C. Murchison (Ed.) Handbook of Social lead a more or less worry free existence Psychology. C. Murchison (Ed.)( pp. 947-972). according to their position in the peck order”, Worcester, Mass.: Clarke University Press. and he gave as an example a low-ranking hen Schjelderup-Ebbe, T., (1975) Contributions to who “was very nervous because of the number the social psychology of the domestic chicken. In of pecks she received. I had the impression that M.W.Schein, (Ed.), Social Hierarchy and she tired herself out in a constant attempt to Dominance. (Benchmark Papers in Animal avoid punishment and to get enough food.” By Behaviour Volume 3, pp. 100-119). Philadelphia: contrast, the high ranking hen, “who was never Dowden, Hutchinson & Ross. bothered by anybody, seemed to feel very well” Wilson, D.S. & Wilson, E.O. (2007) (Schjelderup-Ebbe, 1975, p. 45). He claimed that Rethinking the theoretical foundation of the same applied to other birds, but that the sociobiology. Quarterly Revue of Biology, 82: 327- effects were less in the natural state than in 48. captivity. His observations were largely Wilson, E.O. (2012) The Social Conquest of confirmed by later researchers (Appleby, 1983).

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