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In this straight-forward, objective approach to the sociobiology debate, noted animal behaviorist John Alcock illuminates how sociobiologists study behavior in all species. He confronts the chief scientific and ideological objections head on, with a compelling analysis of case histories that involve such topics as sexual jealousy, beauty, gender difference, parent-offspring relations, and rape. In so doing, he shows that sociobiology provides the most satisfactory scientific analysis of social behavior available today.
Alcock challenges the notion that sociobiology depends on genetic determinism while showing the shortcoming of competing approaches that rely on cultural or environmental determinism. He also presents the practical applications of sociobiology and the progress sociobiological research has made in the search for a more complete understanding of human activities. His reminder that "natural" behavior is not "moral" behavior should quiet opponents fearing misapplication of evolutionary theory to our species. The key misconceptions about this evolutionary field are dissected one by one as the author shows why sociobiologists have had so much success in explaining the puzzling and fascinating social behavior of nonhuman animals and humans alike.
What Is Sociobiology?
Defining the Discipline
This spring morning I climbed to the top of Usery Mountain, which, happily for me, is only a twenty-minute walk up a steep hill in the Sonoran Desert of central Arizona. Once I reached the undulating ridgeline and regained my breath, I walked along the hilltop checking the palo verde trees, creosote bushes, and jojobas to see which plants were occupied by males of a locally common tarantula hawk wasp, Hemipepsis ustulata (fig. 1.1). Males of this large, black-bodied, red-winged species dedicate themselves to a life of ritualistic combat over control of entire trees or shrubs, which the males use as lookouts to scan for approaching virgin females of their species.
This morning many familiar males that I had daubed with Liquid Paper or dots of acrylic paint launched themselves from their territorial stations in pursuit of intruding males, and one even had the special pleasure of responding to a receptive female that flew toward his territorial shrub. This male, marked with yellow dots on his thorax and right wing as a result of an earlier encounter with me and my paints, dashed out after the flying female to grasp her in midair. They fell heavily to the ground and mated without preliminaries. As the female walked a short distance forward, the coupled male toppled over, lying on his back with his wings spread on the gravelly soil. A second male, which had reached the female a few seconds after "yellow dots," attempted without success to mate with the already fully engaged female. After aminute passed, the mating pair separated and yellow dots returned to his perch while his rival continued to probe the female to no good effect until he too flew back to his territorial perch nearby. The female then left to cruise downslope. As I write, she is doubtless out tracking down tarantulas and other large spiders, which she will sting into paralysis before depositing her victim in underground burrows where they will be slowly consumed by the wasp's larval offspring.
Although the hunting behavior of female tarantula hawks is fascinating, the main goal of my project has been to understand the evolution of the species' unusual system for getting females together with males . Why should this be the only tarantula hawk wasp of several local species in which males defend hilltop trees and shrubs in order to have a chance to mate? Why do receptive females of this species choose to visit hilltops and why do they accept the first male that grasps them in midair? Why do males employ a distinctive method of competing for possession of certain palo verdes and other plants, flying up with a rival high into the sky and then diving back down to the site that they both desire, only to repeat the upward flight again and again until one of the two gives up? The tarantula hawk wasp, like many other animal species, experiences episodes of sex and aggression activities that require at least two participants and thus can be considered social. Studying the possible evolutionary causes of these social acts makes me a sociobiologist, according to Edward O. Wilson, who was first to define sociobiology "a the systematic study of the biological basis of all social behavior" .
This is not a narrow definition. Social species come in all sizes and shapes. The members of these species do all sorts of things to one another, inspiring an equally great range of questions about sodality. And here we come to the first of the misconceptions that surround the discipline of sociobiology: the belief that sociobiology concerns itself exclusively or even primarily with human social behavior. The chapter on humans in Wilson's Sociobiology constitutes a mere 5 percent of his book, and the very large majority of today's sociobiologists conduct their research on species other than humans.
Let me emphasize this point with reference to an issue of the technical journal Behavioral Ecology and Sociobiology, which just happens to be on my desk as I write this chapter. "Behavioral ecology" is the study of the evolutionary relationship between an animal's behavior and its environment; sociobiology can be viewed as that component of behavioral ecology that explores the effects of the social environment on behavioral evolution. My copy of Behavioral Ecology and Sociobiology has articles on the social behavior of a damselfish, a katydid, whirligig beetles, assorted primates, a planarian flatworm, and the honey bee. Humans as sociobiological subjects are nowhere to be seen in this issue, although the journal sometimes accept papers on Homo sapiens. The somewhat intimidating titles on the cover of this issue include "Sperm Exchange in a Simultaneous Hermaphrodite" and "Decentralized Control of Drone Comb Construction in Honey Bee Colonies." The various report contain information on such topics as how female flies may (unconsciously) select which sperm get to fertilize their eggs by somehow choosing among the ejaculate of several different partners, and why whirligig beetles assemble in groups on the surface of the streams and lakes they inhabit. Sociobiology is a remarkably wide- ranging discipline in which the complete spectrum of social activities across the animal kingdom is fair game for analysis.
Refining the Definition
Although sociobiology ranges widely across topics and species, it is tightly constrained in terms of its theoretical orientation. Wilson's one-sentence definition of the discipline may suggest that any scientist working on any biological aspect of social behavior qualifies as a sociobiologist. But in reality persons who call themselves sociobiologists, or at least those who tolerate this label, invariably use evolutionary theory as the primary analytical tool for their work. These individuals usually ask and try to answer one basic question: What role did natural selection play in shaping the evolution of this society or that social behavior? Put another way, sociobiologists want to know the evolved function or purpose of whatever aspect of social behavior they are studying.
For example, returning to Behavioral Ecology and Sociobiology, I see that Penelope Watt and Rosalind Chapman wished to understand why whirligig beetles form aggregations of up to thousands of beetles, all zipping back and forth on the water's surface . For the purpose of their study, Watt and Chapman assumed that the beetles' sociality (fig. 1.2) is the product of an evolutionary process dominated by natural selection. They proposed that natural selection in the past favored individual beetles that happened to gather in large groups because these beetles were safer from predators than those with a tendency to live alone or in smaller groups.
The two sociobiologists then tested this proposition experimentally by measuring the rate at which assaults on whirligigs occurred in beetle groups of different sizes held in aquaria with predatory fish. They found that, at least under these experimental conditions, the risk to any individual beetle of coming under attack by a fish in a given period decreased with increases in the size of the aggregation to which the beetle belonged. This finding provides support for the hypothesis that whirligig societies form because social individuals gain survival advantages. If this relationship held in the past, as it apparently does in the present, and if individuals differed in their hereditary tendency to seek out the company of others, relatively social whirligigs in the past would have tended to live longer and leave more descendants to carry on their special social attributes than relatively solitary individuals. If so, a process based on differences in reproductive success in the past would then have shaped the social behavior of today's whirligigs, which are subject to yet another round of selection with the potential to change or maintain the current social nature of these animals. Although Watt and Chapman's evolutionary hypothesis can be tested in many other ways, the point for the moment is that they approached the problem of whirligig sociality from a particular perspective, a historical one, in an attempt to identify the reproductive advantage that social tendencies conferred on individual beetles.
But the evolutionary angle is not the only possible biological approach to social behavior. Another kind of biological question about social behavior exists, one that does not revolve directly around evolutionary events: How does the internal machinery of life work to produce particular results? Whirligig social behavior is potentially subject to a sort of mechanical explanation. The beetles clearly possess internal mechanisms that enable them to react to their fellow beetles in a particular way and to stay together in groups once they have formed. The mechanisms underlying whirligig social responses include the neurophysiological systems, the wiring, of the insects in question. But Watt and Chapman did not attempt to learn how the nervous system of the beetles worked to provide sensory inputs from the environment, which could be used to make neural "decisions" about which batteries of muscles to control in ways that lead whirligigs to gather together. Nor did Watt and Chapman consider how the neural networks of the beetle were assembled as the beetle metamorphosed from a fertilized egg to a functional adult. Solving this problem involves examination of the genetic-developmental mechanisms that result in the growth of the beetle into a complex multicellular organism of a particular design.
Studies focusing exclusively on how an animal's internal machinery works are not the province of sociobiologists, a point that Wilson made in the first chapter of Sociobiology . There he presents a diagram of the relationships between the various biological disciplines that address social behavior (fig. 1.3). Note that according to this diagram the disciplines of sociobiology and behavioral ecology are closely allied; in turn, they are linked with population biology, whose central concern is the description of the genetics of entire populations and the response of gene pools to evolutionary processes, including but not limited to natural selection. These then are the evolutionary disciplines important for an understanding of social behavior. Were Wilson to write an update of Sociobiology today, he would also place the newly named field of human evolutionary psychology on the right-hand side of the diagram as a subdiscipline of sociobiology, which in turn would be shown as part of an overarching behavioral ecology. Evolutionary theory is at the heart of all three entities .
Evolutionary psychology provides a bridge of sorts to the study of the internal devices that make social behavior possible. On the left-hand side of Wilson's diagram, he placed those disciplines that delve into the operating rules of the machinery of behavior. Integrative neurophysiology examines the interaction between sensory systems and those other internal mechanisms that drive the muscles, which need to be controlled if an animal is to behave. Integrative neurophysiology in turn rests on a foundation of cell biology with its attempt to identify how chemical events within cells regulate the development of the organism, the operation of nerve cells, and the transmission of genes to sperm or eggs, among many other things. In the jargon of biologists, studies of how cellular mechanisms and system-operating rules influence behavior are classified as proximate research, which examines the immediate causes of the traits of interest. In contrast, questions about the adaptive (reproductive) value of behaviors are labeled ultimate questions, not because they are more important than proximate ones but because they are different, dealing with the long-term historical causes of the special abilities of species.
So, for example, I was engaged in proximate, not ultimate, research when I studied what motivated territorial tarantula hawks to fight with intruders, investing time and energy in spiral flights with certain opponents . My colleague Winston Bailey and I knew that territory-holding males of many other species appear to become increasingly motivated to fight with intruders the longer the resident males have held their territories, something that has been labeled the "residency effect" by other researchers studying the same phenomenon in other species. To test whether the residency effect applied to tarantula hawks, we removed territory owners and held them in a cooler until a rival male had established himself on the experimentally vacated territory. We found that, as expected, the longer we let the new male hold his site before releasing the old resident, the more willing the newcomer was to engage the original territory holder in a long series of spiral flights when he returned to reclaim his perch (fig. 1.4). In other words, one of the immediate causes of aggression among male tarantula hawks has to do with the psychological effects of being in control of a territory. The wasps evidently possess internal mechanisms that record how long they have held a site, and this information somehow influences the neural networks controlling territorial defense. This kind of study falls outside the domain of sociobiology if its only goal is to identify the proximate operating rules of physiological systems that generate a behavioral effect.
Proximate research on the residency effect can, however, take on an ultimate character and thus becomes part of sociobiology, when the question changes from how does the internal machinery work to why does the machinery work that way. Do males experience a reproductive advantage as a result of having proximate mechanisms that enable them to measure how long they have held a territory and that motivate them to defend a desert shrub or tree accordingly? If so, why? Various hypotheses exist on this point, and some have been tested for species other than tarantula hawks but not yet for Hemipepsis ustulata. My point here is not to answer the ultimate question about the residency effect but to make the case that one can ask purely proximate and purely ultimate questions, each category dealing with different but complementary aspects of a biological phenomenon.
Let me repeat that: ultimate causes are not somehow superior to proximate ones or vice versa. In the biological arena, "ultimate" does not mean "the last word" or "truly important" but merely "evolutionary." The existence of the two terms, proximate and ultimate, helps us acknowledge the fundamental difference between the immediate causes for something and the evolutionary causes of that something [11,286]. 286].
Biologists also realize, however, that knowing about the connections between proximate and ultimate causes is as important as understanding the difference between them. The cellular and physiological mechanisms in today's whirligig beetles and tarantula hawks have persisted to the present because these mechanisms happened to promote reproductive success in the past. Some traits have regularly advanced an individual's chances of getting its genes into the next generation while others have not. The historical differences in the genetic success of individuals with different attributes determined which genes managed to survive to the present. These genes promote the development of particular kinds of neural networks in today's organisms, which provide them with the machinery of behavior. Thus, proximate and ultimate causes of social behavior (and all other biological traits) intertwine across history. The machinery of reproductive success promotes its long-term persistence; in contrast, internal mechanisms that predispose individuals to fail at reproduction wind up in the junk heap of history.
Therefore, to say that proximate and ultimate issues in biology are different does not mean that sociobiological approaches cannot be applied to genetic-developmental or physiological-psychological matters. For example, as noted above, the new field of evolutionary psychology analyzes proximate mechanisms of human behavior from an explicitly evolutionary perspective, asking questions about why we possess particular psychological attributes and seeking ultimate answers in terms of the contribution these mechanisms might make or have made to the reproductive success of individuals. No internal proximate mechanism of social behavior exists that cannot be explored in terms of its adaptive value, just as no adaptive behavior occurs whose underlying proximate causes cannot be investigated to good effect.
Sociobiology before Wilson
Despite Wilson's explanation of sociobiology as a branch of evolutionary biology, the hoopla and controversy surrounding the publication of Sociobiology apparently induced many to accept another misconception about sociobiology, namely, that Wilson produced a idiosyncratically novel, and therefore potentially suspect, theory of social behavior, just one more ivory tower concoction to be added to the pot of competing arguments. However, anyone who sits down with the book will soon realize that it is a massive summary review of the research of other scientists who have employed Darwinian evolutionary theory to make sense of social behavior. Wilson's role was one of synthesis, no mean task since it required (1) an ability to read and digest the vast evolutionary literature on social behavior, (2) a clear and useful organizational scheme, and (3) the readiness to review the major themes in sociality and explain how these made sense in the light of evolutionary theory. Wilson achieved all these things in Sociobiology, and so he was fully entitled to give a new, compact, and memorable label to what others at the time were calling "ethology" or "the study of behavioral evolution."
But the theoretical foundation of the book and its approach to explaining social behavior were far from new. The evolutionary analysis of behavior began in 1859 with the publication of On the Origin of Species by Charles Darwin . It is common in evolutionary circles to trace the lineage of one's position to the first and greatest evolutionist of them all, thereby investing one's view with the imprimatur of authority, sometimes with justification, other times less so. But in case, we need not entertain doubt that Darwin was a sociobiologist because he explicitly considered how social insect colonies might have evolved, and he did so long, long before E. O. Wilson was born. The sterile workers in these colonies offer a major challenge for the evolutionist, as Darwin recognized full well, since the worker lifestyle has persisted within certain species for eons despite the inability of workers to reproduce, which would seem to prevent them from passing on the hereditary basis for their sterility.
Darwin offered a logical solution to the puzzle: If sterile workers promoted the survival and reproductive success of other family members, then any distinctive hereditary attributes that they, the sterile workers, possessed would be donated to subsequent generations by others in their family lineage (which we now know have some of the same genes as the sterile individuals). In this way, the capacity for sacrifice in the service of relatives could persist over evolutionary time, much in the same way that the desirable features of domesticated beef cattle destined exclusively for the dining room table could be maintained by selective breeding of cows and bulls that were related to those headed for the slaughterhouse .
Darwin's solution to this challenging problem was brilliant, all the more so because he did not have access to modern genetics. Substantial improvements to his explanation for sterile insect castes did not arrive until 1964, more than a century after the publication of On the Origin. But for now, we need only note that Darwin's work on this matter qualifies him as a sociobiologist because he was interested in social behavior and, more importantly, because he brought modern evolutionary thinking to the table. Without Darwinian theory, there could be no sociobiology.
Evolutionary theory is not controversial among scientists. True, some dispute still exist about such moderately arcane issues as whether evolutionary change is gradual or abrupt, with allied arguments about what "gradual" and "abrupt" mean in evolutionary time scales. But the fundamental propositions of evolutionary theory are universally accepted by biologists just as certain fundamental laws of physics or chemistry are understood to be true by physicists and chemists. No biologist lies awake at night worrying about whether evolutionary change has indeed occurred. Essentially all professional biologists agree that living species are descended from extinct ancestors in a tree of life that traces back to a single-celled ancestor that lived roughly 4 billion years ago. Almost all biologists accept the idea that natural selection is the ultimate "force" behind the evolution of the many adaptations that characterize all living things .
|Ch. 1||What Is Sociobiology?||7|
|Ch. 2||What Sociobiologists Study||23|
|Ch. 3||Sociobiology and Genes||41|
|Ch. 4||Sociobiology and Science||57|
|Ch. 5||Science and Reality||81|
|Ch. 6||What Have Sociologists Discovered?||93|
|Ch. 7||The Problem with Cultural Determinism||129|
|Ch. 8||Sociobiology and Human Culture||149|
|Ch. 9||The Practical Applications of Sociobiology||189|
|Ch. 10||The Triumph of Sociology||217|