chapter 1

We are all one with creeping things;
And apes and men
Blood-brethren.

From ‘Drinking Song’ by Thomas Hardy

The consensus among the scientific community is that the Earth is a planet orbiting a fairly typical star, one of many billions of stars in a galaxy among billions of galaxies in an expanding universe of enormous size, which originated about 14 billion years ago. The Earth itself formed as the result of a process of gravitational condensation of dust and gas, which also generated the Sun and other planets of the solar system, about 4.6 billion years ago. All present-day living organisms are the descendants of self-replicating molecules that were formed by purely chemical means, more than 3.5 billion years ago. The successive forms of life have been produced by the process of ‘descent with modification’, as Darwin called it, and are related to each other by a branching genealogy, the tree of life. We human beings are most closely related to chimpanzees and gorillas, with whom we shared a common ancestor 6 to 7 million years ago. The mammals, the group to which we belong, shared a common ancestor with living species of reptiles about 300 million years ago. All vertebrates (mammals, birds, reptiles, amphibia, fishes) trace their ancestry back to a small fish-like creature that lacked a backbone, which lived over 500 million years ago. Further back in time, it becomes increasingly difficult to discern the relationships between the major groups of animals, plants, and microbes, but, as we shall see, there are clear signs in their genetic material of common ancestry.

Less than 450 years ago, all European scholars believed that the Earth was the centre of a universe of at most a few million miles in extent, and that the planets, Sun, and stars all rotated around this centre. Less than 250 years ago, they believed that the universe was created in essentially its present state about 6,000 years ago, although by then the Earth was known to orbit the Sun like other planets, and a much larger size of the universe was widely accepted. Less than 150 years ago, the view that the present state of the Earth is the product of at least tens of millions of years of geological change was prevalent among scientists, but the special creation by God of living species was still the dominant belief.

The relentless application of the scientific method of inference from experiment and observation, without reference to religious or governmental authority, has completely transformed our view of our origins and relation to the universe, in less than 500 years. In addition to the intrinsic fascination of the view of the world opened up by science, this has had an enormous impact on philosophy and religion. The findings of science imply that human beings are the product of impersonal forces, and that the habitable world forms a minute part of a universe of immense size and duration. Whatever the religious or philosophical beliefs of individual scientists, the whole programme of scientific research is founded on the assumption that the universe can be understood on such a basis.

Few would dispute that this programme has been spectacularly successful, particularly in the 20th century, which saw such terrible events in human affairs. The influence of science may have indirectly contributed to these events, partly through the social changes triggered by the rise of industrial mass societies, and partly through the undermining of traditional belief systems. Nonetheless, it can be argued that much misery throughout human history could have been avoided by the application of reason, and that the disasters of the 20th century resulted from a failure to be rational rather than a failure of rationality. The wise application of scientific understanding of the world in which we live is the only hope for the future of mankind.

The study of evolution has revealed our intimate connections with the other species that inhabit the Earth; if global catastrophe is to be avoided, these connections must be respected. The purpose of this book is to introduce the general reader to some of the most important basic findings, concepts, and procedures of evolutionary biology, as it has developed since the first publications of Darwin and Wallace on the subject, over 140 years ago. Evolution provides a set of unifying principles for the whole of biology; it also illuminates the relation of human beings to the universe and to each other. In addition, many aspects of evolution have practical importance; for instance, pressing medical problems are posed by the rapid evolution of resistance by bacteria to antibiotics and of HIV to antiviral drugs.

In this book, we shall first introduce the main causal processes of evolution (Chapter 2). Chapter 3 provides some of the basic biological background, and shows how the similarities between living creatures can be understood in terms of evolution. Chapter 4 describes the evidence for evolution derived from Earth history, and from the patterns of geographical distribution of living species. Chapter 5 is concerned with the evolution of adaptations by natural selection, and Chapter 6 with the evolution of new species and of differences between species. In Chapter 7, we discuss some seemingly difficult problems for the theory of evolution. Chapter 8 provides a brief summary.

preface

Cognitive neuroscience, the study of brain-behavior relationships, is historically old in its attempt to map the brain. As a discipline it is flourishing, with an increasing number of functional neuroimaging studies appearing in the scientific literature daily. Unlike biology and even psychology, however, the cognitive neurosciences have only recently begun to apply evolutionary theory and methods. Approaching cognitive neuroscience from an evolutionary perspective allows scientists to apply a solid theoretical guidance to their investigations, one that can be carried out in both human and nonhuman animals. This book represents the first formal attempt to document the burgeoning field of evolutionary cognitive neuroscience. Introduction to Evolutionary Cognitive Neuroscience All organisms were and continue to be subject to the pressures of natural and sexual selection. These pressures are what formed all biological organs and hence also carefully crafted animal nervous systems—the seat of animal and human behavior, and the means by which organisms employ information-processing programs to adaptively deal with their environment. This theory was first formalized by Darwin (1859) in his seminal book, On the Origin of Species by Natural Selection. Unlike the theoretical work of early psychologists and behavioral scientists such as Skinner and Watson, which envisioned organisms as “blank slates” capable of making an infinite number of associations, evolutionary metatheory is beginning to shed light on this flawed theoretical approach to behavior analysis (see Barkow, Cosmides, & Tooby, 1992; Buss, 2005; Cosmides & Tooby, 2005). In fact, many of the emerging studies are contending directly with the standard social science model of psychology, namely, that organisms possess general-purpose learning mechanisms and that biology plays little if any role in the manifestation of behavior. Some of the first psychological studies to demonstrate that learning is not mediated by general-purpose learning mechanisms were conducted several decades ago and mark what might be considered the beginning of evolutionary thinking in psychology; they also contributed greately to what has become known as the cognitive revolution. In his landmark study, Garcia discovered that animals learned to avoid novel food products that made them ill in as little as one learning conditioning trial, something that had not been demonstrated with any other stimulus class previously. Labeled conditioned taste aversion, this effect describes an adaptive problem that has since been demonstrated in almost every species tested (the exception to this rule appears to be crocodilians; see Gallup & Suarez, 1988). This adaptation serves an important function: don’t eat food that makes you ill, or you might not survive to reproduce and pass on your genes. In other words, being ill could result in a number of fitness disadvantages such as death, inability to avoid predation, inability to search and secure mates, and loss of mate value. In a similar discovery, Seligman demonstrated what he referred to as prepared learning. Prepared learning is a phenomenon in which it is easier to make associations between stimuli that possess a biological predisposition to be conditioned because of a role these stimuli played in an organism’s evolutionary history. Seligman and his colleagues demonstrated that it was much easier for humans (and animals) to form conditioned emotional responses and associative fear responses to evolutionarily relevant threats such as snakes, insects, and heights than it took to condition fear to present-day threatening stimuli that subjects were much more likely to be have encountered and be harmed by, such as cars, knives, and guns. In other words, it was easier to condition humans to fear snakes, spiders, and heights than it was to condition them to fear guns, cars, and knives. These two series of studies demonstrated that psychological traits, like the design of bodily organs, were crafted by evolutionary forces into adaptations that allowed our ancestors to flourish. That is, the information-processing mechanisms designed to deal with situations such as poisonous food or potential threats to survival evolved as part of our ancestors’ recurrent experience with such situations. These studies refute a key premise of the standard social science model, emphasizing that there is no general-purpose learning mechanism. Rather, all learning is a consequence of carefully crafted modules dedicated to solving specific evolutionary problems (see Barkow, Cosmides, & Tooby, 1992; Pinker, xiv Preface 2002). Our brains have evolved to be efficient problem solvers, and the problems they are designed to solve are those that our ancestors recurrently faced over human evolutionary history. Hence, those among our ancestors who were psychologically adaptated to solve these problems survived and passed the genes for those traits on to offspring. Recently, evolutionary metatheory has been applied directly to investigations of the cognitive neuroscience kind. For example, O’Doherty, Perrett, and colleagues (2003) have begun to investigate neural correlates of facial attraction. O’Doherty and colleagues discovered that the orbitofrontal cortex appears to be activated when a person finds a face attractive, which suggests that facial attractiveness activates a reward system in the brain. Further, Baron-Cohen and colleagues have demonstrated that there is a neural module dedicated to processing socially relevant information. Baron-Cohen and colleagues demonstrated that the ability to conceive of others’ mental states appears to be (1) a highly modularized neurocognitive process and (2) affected by certain neuropsychiatric pathologies (e.g., autism). Platek and colleagues have extended initial behavioral findings of sex differences in reaction to children’s faces to the cognitive neuroscience arena, demonstrating sex differences in functional neural activation associated with reactions to children’s faces. They found that males but not females showed activation in left frontal regions of the brain when viewing self-resembling child faces, suggesting that males inhibit negative responses to children’s faces as a function of facial (phenotypic) resemblance. Perhaps the most convincing set of studies demonstrating evolved structures or modules dedicated to social interaction and exchange has come from Cosmides, Tooby, and colleagues at the Center for Evolutionary Psychology in Santa Barbara, California. By modifying a logic problem known as the Wason Selection Task to reflect evolutionarily important social interactions (e.g., cheater detection), Cosmides, Tooby, and colleagues have demonstrated that the human brain appears to have evolved a cheater detection mechanism that is extremely efficient. They have furthered the evidence for a cheater detection module by showing that one can incur impairment (i.e., brain trauma) of performance on cheater detection problems but remain relatively unimpaired on other types of problem solving. Their data suggest that parts of the limbic system are implicated in the ability to detect cheaters in social interactions. The investigation of an evolutionary cognitive neuroscience extends beyond humans, however. Hauser, Hare, and a number of other researchers have been studying social behavior and social exchange xv Preface in nonhuman primates and have demonstrated an apparent cognitive continuity among primate phyla in the ability to understand the mental states of others. Daniel Povinelli’s ongoing research program has been particularly powerful at demonstrating phylogenetic and ontogenetic trajectories for the capacity for theory of mind and self-awareness among nonhuman primates. These new investigations, by applying cognitive neuroscientific methods to answer questions posed from an evolutionary theoretical perspective, are crafting a new understanding of how the mind and brain evolved. In fact, they call into question much of the psychological investigation that was conducted throughout the twentieth century. This book is the first to present, in an organized overview, the way in which researchers are beginning to wed the disciplines of evolutionary psychology and cognitive neuroscience in order to provide new data on and insights into the evolution and functional modularity of the brain. Each of the six sections in this book addresses a different adaptive problem. Part I consists of three chapters that outline the basic tenets of an evolutionarily informed cognitive neuroscience. These chapters discuss evolutionary theory as it can be applied to behavior and cognition, as well as modern technological advances and methods that are available to the cognitive neuroscientist for the investigation of the adapted mind. In Chapter 1, Aaron Goetz and Todd Shackelford present an overview of the basic principles of evolution—natural and sexual selection, fitness, and adaptation—as they apply to behavior and cognition. In Chapter 2, Robin Dunbar expands on this presentation by describing a theory known as the social brain hypothesis and discusses the major social evolutionary forces that gave rise to big-brained humans and adaptive brains. Chapter 3, by Shilpa Patel and colleagues, outlines the current methodological approaches used in evolutionary cognitive neuroscience. Part II broaches the topic of neuroanatomy from an ontogenetic and phylogenetic perspective. In Chapter 4, Valerie Stone considers why big-brained organisms have extended ontogenetic and brain developmental periods. In Chapter 5 William Hopkins considers hemispheric specialization in our closest living relative, the chimpanzee. In Chapter 6, J. Philippe Rushton and C. Davison Ankney review their studies on the relationship between brain size and intelligence. To close Part II, Lori Marino in Chapter 7 discusses the current state of the science in cetacean brain evolution. xvi Preface Part III tackles the topic of reproduction and kin recognition. Chapter 8, by Russell Fernald, discusses the degree to which social environments can exert effects on reproductive behaviors. He draws on studies in his own laboratory on fishes and other nonhuman organisms, as well as on classic studies of this effect. In Chapter 9, Steven Platek and Jaime Thomson describe their recent findings supporting a sex difference in neural substrates involved in the detection of facial resemblance, and discuss what these findings might mean for kin selection or detection and paternal uncertainty. In Chapter 10, Helen Fisher and J. Anderson Thomson, Jr., summarize their recent studies with fMRI to identify the neural correlates of romantic attraction and lust. In Chapter 11, David Newlin outlines his SPFit model for drug addiction, which posits that drugs of addiction capitalize on evolutionary predispositions for reward- and reproductive-based behavioral and neural mechanisms. Part IV addresses two well-known and well-researched areas: spatial cognition and language. David Puts, Steven Gaulin, and Marc Breedlove in Chapter 12 discuss sex differences in spatial abilities, paying particular attention to the endocrinological aspects associated with sex differences. In Chapter 13, Ruben Gur and colleagues extend the discussion of the evolution of sex differences in spatial cognition by summarizing current literature showing sex differences in neural substrates involved in solving spatial tasks. To conclude Part IV, Michael Corballis in Chapter 14 describes a theory of language evolution that draws on recent findings in animal and human neuroscience, especially the discovery of mirror neurons. Part V takes up the topic of self-awareness and social cognition. In Chapter 15, Laurie Santos and her colleagues summarize their recent research showing that nonhuman primates possess the capability for social cognition, such as rudimentary theory of mind. In Chapter 16, Farah Focquaert and Steven Platek discuss their theory about the evolution of self-processing, introducing evidence from the nonhuman primate literature as well as from their own functional neuroimaging studies. Simon Baron-Cohen in Chapter 17 then presents his systemizingempathizing theory for the development of theory of mind and describes how the model can be used to help classify individuals along this spectrum, with particular reference to autism and autism spectrum conditions. In Chapter 18, the discussion of self-awareness and social cognition takes a different direction describing the evolution of deception. Sean Stevens and colleages outline the “dark side of consciousness” theory, xvii Preface which links the capacity for deception to an intact self-awareness. Finally, Stephen Kosslyn in Chapter 19 presents a new theory for human motivation in which he describes social prostheses and reconsiders the self in light of this social network. The volume concludes with Part VI, which considers the ethical implications for evolutionary cognitive neuroscience.