More Than Kin and Less Than Kind: The Evolution of Family Conflict.—Douglas W. Mock. 2004. The Belknap Press of Harvard University Press, Cambridge, MA, and London, England. ISBN 0-674-01285-2. $27.95 (cloth).
This book is a fascinating read, using evolutionary theory to explain why family members behave towards each other as they do. The author is a long-time student of family relationships, particularly in egrets and herons, and particularly when the feathered familial relations go sour. Given his background and the substantial academic contributions he has made in the field, Mock is well placed to expound on the subject of how genetic relationships affect cooperation and competition between relatives.
The main thread of the book weaves a well-integrated and logical path through various subtopics. The text is cogently written, and complex arguments are carefully and clearly outlined. The reader is often referred to the historical context in which important theoretical or conceptual advances were made, which provides an interesting backdrop. Egrets and herons dominate as the case studies used to illustrate the theoretical arguments, but the book is also generously peppered with a smorgasbord of taxonomically diverse empirical examples. In addition, Mock sidesteps regularly with delightful biological and personal tangents that provide lighter and often amusing moments, yet without interrupting the flow of the book.
The prologue introduces the content and aim of the book well—to use the logic of natural selection to explain family relationships. It also sets up the tone and style of the text, and the promise of an entertaining and interesting read encourages one to settle more deeply into a comfy chair and to get ready for a prolonged session!
The first four chapters explain some important foundation concepts that underpin the rest of the book. In particular, Mock explains how the theory of kin selection provides the template for determining the limits of both ‘cooperative’ as well as ‘selfish’ behavior within families, as well as why the ‘rules’ of kin selection mean that family members may have vested interests in the outcome of interactions between other relatives, even if they do not involve the focal family member directly. The most obvious example of this is that parents may have an interest in how conflict is resolved between two offspring if it affects their own lifetime reproductive success. Hamilton's Rule, how to calculate the coefficient of relatedness between individuals, and what sex does to genes, and thus relatedness, are all clearly explained. Chapter Three also introduces the idea of the ‘nursery’—a confined arena in which family members (especially siblings) interact. This idea is important, because attributes of the nursery, especially its size, shape, and context, can partly determine the nature and the outcome of familial interactions. Chapter Three also presents one of the more dramatic examples of sibling rivalry in action, in the form of sand tiger sharks, where about 17 000 eggs develop inside the mother into embryos with teeth, and over the course of gestation the number is gradually whittled down through rather unfriendly sibling interactions to just one live-born young!
Chapter Four is particularly interesting. It encapsulates the history of major leaps in evolutionary theory (and includes some of the relevant historical context), such as the development of game theory (where the best thing for an individual to do depends critically on what the other individual does), parent-offspring conflict, and sex ratio theory (why the production of sons and daughters may have different genetic benefits for parents under some circumstances). This chapter also describes many of the various hypotheses that were generated as a direct result of these important conceptual advances. In particular, it runs through a number of examples such as kin facilitation and the insurance hypothesis, which implicitly share the idea that depending on the context, offspring may have nonequivalent values, and consequently that some offspring are more expendable than others.
This step in the thread of the book provides the link with the following six chapters, which parade through the spectrum of sibling interactions, from obligate mortality (with or without overt fighting, and which perplexed ecologists for so long), to facultative siblicide (where mortality is context or environmentally determined), to scramble competition. Throughout this parade, Mock explains the situation from the viewpoints of the parents, as well as from the perpetrating and victimized offspring. He successfully interweaves the concepts explained earlier in the book (of kin selection, parent-offspring conflict, etc.) with some new ideas such as the trade-off between offspring quantity and quality, the dichotomy between insurance versus resource-tracking hypotheses for brood reduction, the trade-off between the success of one breeding attempt versus that of lifetime reproductive success, the concept of parental gambling with respect to offspring production, and also the idea of marginal offspring.
Chapters Eleven and Twelve take a closer look at parent-offspring conflict, partly to elaborate on what seems to be one of the author's bugbears—he loves the theory but is still searching for a good example of it. He believes that although evolutionary conflict exists (that is, the parent and the offspring have different preferred outcomes), in practice there is no conflict, because the parent does exactly what it wants, sometimes at the offspring's expense. For instance, in the well-known example of mother-offspring squabbling over the termination of suckling in red deer, despite any protestations on the part of the calf, the mother always has the physical advantage and therefore the upper hand. I was a little unconvinced by his argument, as I do not see the need for a clear ‘win’ on the part of the offspring—surely modifying the parental behavior is enough. If the red deer calf was completely passive, and did not pester its mother continuously, it seems likely to me that suckling would terminate earlier. Of course, measuring the effect of offspring sulkiness on the outcome of many of these conflict situations is difficult. Despite his reservations, Mock describes some cases that he believes will be textbook examples of parent-offspring conflict, particularly the Queen-Worker conflict over the sex ratio (and reproduction) in Hymenopterans. In telling this story, he relates the quirky effects of haplodiploidy on the social systems, sex ratios, and work roles in a clear and interesting way.
From here, Mock moves onto conflict between mates over reproductive investment, and then the idea of Progeny Choice, before finishing in Chapter Fifteen with an assortment of what he calls ‘complex and weird’ examples of different manifestations of familial interactions, including black storks, pigs, burying beetles, lions, spadefoot toads, and Laughing Kookaburras, which are especially interesting as they show extremes of both cooperative behaviour (offspring delay dispersal and breeding to help their parents raise more young), as well as selfish behavior (given the right circumstances, the chicks are seriously murderous towards siblings).
By explaining complex theory in a clear and accessible way, and by using an entertaining range of examples and anecdotes, this book will be of interest to a wide audience, from university undergraduates to interested naturalists. Its synthesis of several strands of theory with a wide-ranging review of empirical studies also makes it a useful and enjoyable read for professional ecologists, including those involved in the fields of sibling rivalry and parent-offspring conflict. I strongly recommend this book—you'll enjoy it!
