American Scientist

Cooperation Among Animals: An Evolutionary Perspective. Lee A. Dugatkin. 221 pp. Oxford University Press, 1997. $60.

Over the past 2,000 years, few topics in biology have fostered as much debate as cooperation. Perhaps we remain fascinated because, like Aristotle, we suspect that human societies require cooperative interactions to function. Consequently, understanding how cooperation has evolved in other animals may give us insight into our own past. The evolutionary process that gives rise to cooperation is far from obvious because the benefit to an individual for helping others is often obscure. Charles Darwin recognized that sterile social insects represent an acute version of this dilemma, but many other less conspicuous examples are known. Although some cooperative behaviors among ants or birds have been reviewed recently elsewhere, to my knowledge this concise, readable book provides the first comprehensive review of cooperation among animals.

Lee Dugatkin goes beyond a taxonomic survey, however, and provides a wonderful review of philosophical and biological ponderings on the nature of cooperation. This early history sets the stage for introducing four contemporary alternative, although not exclusive, mechanisms that have been invoked to explain both the evolution and persistence of cooperation in animals: kin selection, group selection, reciprocity and by-product mutualism. Those familiar with the theoretical foundations of these ideas may find Dugatkin's treatment terse, but he succeeds in outlining the essential features of the theory behind each idea. Furthermore, he incorporates each of these historically disparate ideas into a single evolutionary game he terms "the cooperator's dilemma." This game is a simple generalization of the well-known and extensively studied prisoner's dilemma. Dugatkin's rationale for presenting the cooperator's dilemma is to illustrate how, in principle, different mechanisms of cooperation can be identified in extant species. Thoughout the remainder of the book he proceeds to examine examples of putative cooperation among nonhuman animals using this heuristic.

With nearly a thousand references, a major attraction of this book is the comprehensive review of cooperative behaviors by different species of fishes, birds, nonprimate mammals and nonhuman primates. Little-known but intriguing examples abound. Yellowtail fish have been observed hunting jack mackeral in coordinated schools in striking parallel to the hunting behavior of some hawks and pack-hunting mammals. Group foraging, alloparental care, group defense, vigilance, food sharing and allogrooming also are discussed. These examples provide a persuasive case that cooperation is common among vertebrates.

Dugatkin limits his discussion of cooperation in insects to a few issues in eusocial species—for example, the evolution of reproductive altruism, worker policing, the hive as a super-organism and colony founding. While his review of these topics is nicely done, I was disappointed not to find examples of cooperative behaviors in other invertebrates, such as spiders or snapping shrimp. Also excluded from discussion are cooperative interactions betwen species or other levels of organization cells within an organism, organelles within cells or genetic material within organelles. The result is a cohesive, although somewhat restricted, view of cooperation in nature.

A major asset and weakness of this book is Dugatkin's attempt to categorize examples using alternative evolutionary mechanisms. Although I applaud his efforts to identify the requisite ecological and behavioral factors likely to influence cooperation in each example, in many cases the evidence is simply not up to the task at hand. Controversial evolutionary mechanisms, such as group selection and reciprocity, are sometimes offered when insufficient evidence is available to evaluate their merit. Nevertheless, from my perspective, Dugatkin has succeeded both in summarizing what we currently know about cooperation in animals and, perhaps more importantly, what remains to be learned.—Jerry Wilkinson, Zoology, University of Maryland