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The Lives of the Brain

The Lives of the Brain: Human Evolution and the Organ of Mind

Copyright Date: 2009
Published by: Harvard University Press
Pages: 352
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  • Book Info
    The Lives of the Brain
    Book Description:

    Though we have other distinguishing characteristics (walking on two legs, for instance, and relative hairlessness), the brain and the behavior it produces are what truly set us apart from the other apes and primates. And how this three-pound organ composed of water, fat, and protein turned a mammal species into the dominant animal on earth today is the story John S. Allen seeks to tell.

    eISBN: 978-0-674-05349-6
    Subjects: Health Sciences, Ecology & Evolutionary Biology, Developmental & Cell Biology

Table of Contents

  1. Front Matter
    (pp. i-vi)
  2. Table of Contents
    (pp. vii-xii)
  3. CHAPTER ONE Introduction
    (pp. 1-5)

    A simple narrative of the evolutionary history of the human brain could be written like this: about 6 million years ago, the first hominids started walking on two legs and thereby distinguished themselves from their ape cousins, while maintaining brains that were about one-third the size seen in modern humans. For the next 3 to 4 million years, the human brain did not become significantly larger, although it may have become slightly larger as a proportion of body size. About 2 million years ago, some hominids evolved with brains somewhat larger than those of an ape. Simple stone tools appear...

  4. CHAPTER TWO The Human Brain in Brief
    (pp. 6-43)

    We humans are easily impressed by our own brains, and not without some justification. Human brains consist of a hundred billion neurons, each with connections to tens of thousands of other neurons. The number of possible connections among these neurons defies comprehension. Furthermore, these neurons are not simply connected to each other like bricks in a wall: They are in communication via an electrochemical junction at each synapse. Our neurons coalesce into interactive networks whose concerted actions regulate the behavior of the human body from breathing to composing music. At any given instant, the brain takes an abundance of sensory...

  5. CHAPTER THREE Brain Size
    (pp. 44-81)

    Size is the most fundamental issue in the study of human brain evolution. The focus on brain size is in part an artifact of the paleontological record, which preserves information about the volume of the brain but precious little else. Anthropologists seek to reconstruct the unique biological history of our species by studying the fossil record, and an important part of that history has been the relative expansion of the brain. Since the nineteenth century, anthropologists and others have attempted to understand the relationship between brain volume and cognitive ability. The framework for this understanding has generally been provided by...

  6. CHAPTER FOUR The Functional Evolution of the Brain
    (pp. 82-119)

    In his battles with the phrenologists, the French anatomist Pierre Flourens (1794–1867) enthusiastically argued that the brain was a single, unified structure that showed no evidence of functional localization. As he wrote in hisPhrenology Examined(1846): “It has been shown by my late experiments, that we may cut away, either in front, or behind, or above, or on one side, a very considerable slice of the hemisphere of the brain, without destroying the intelligence … On the other hand, in proportion as these reductions by slicing away the hemispheres are continued, the intelligence becomes enfeebled, and grows gradually...

  7. CHAPTER FIVE The Plastic Brain
    (pp. 120-147)

    The French anatomist Paul Broca gained lasting, eponymous fame for using the lesion method to discover one of the areas of the brain important in the production of speech (Figure 5.1). He has achieved another level of notoriety, however, through the writings of Stephen Jay Gould (1981) and others, as an exemplar of a strongly racialist and biologically deterministic nineteenth-century anthropology, in which behavioral and cultural attributes were seen to be a direct function of biological race. Along with the likes of the American proto-anthropologist Samuel George Morton, whose work came earlier, Broca was known for advocating the position that...

  8. CHAPTER SIX The Molecular Evolution of the Brain
    (pp. 148-176)

    Even more than neuroscience, molecular biology is a discipline that seems to generate revolutionary new discoveries or breakthroughs on a regular basis. These revolutionary developments inevitably have their effects on allied disciplines, where they may mesh more or less well with prevailing paradigms. The study of human evolution is one of the allied disciplines that has benefited greatly from these molecular advances, although the result has included some tension between molecular biological and more traditional practitioners within biological anthropology. The molecular revolutions started to have a real impact on human evolutionary studies beginning in the 1960s, and it seems that...

  9. CHAPTER SEVEN The Evolution of Feeding Behavior
    (pp. 177-201)

    About 60 million years ago, the earliest primates distinguished themselves from the many other small mammals living at that time and established the order that would eventually lead to us. But what was distinguishing about them? Although contemporary primates are quite diverse, almost all of them share a suite of anatomical characteristics that serves to separate them from other mammals. Included among these are features such as grasping hands with opposable thumbs or big toes, nails instead of claws, and a generalized body plan and dentition. Primates also possess relatively large brains compared to other mammals. This relative increase in...

  10. CHAPTER EIGHT The Aging Brain
    (pp. 202-231)

    The quest for longer life continues unabated. Indeed, the relative comforts of contemporary society, where food is plentiful, labor is largely nonmanual, and infectious disease is under some measure of control, seem to have intensified our interest in living longer and better. Of course, quantity and quality of life are two different things. We celebrate people who live to 100, 110, or even 120 years, but truth be told, most of us would have a hard time envying the lives of infirmity and dependence that most centenarians experience. Increases in the life span are only desirable if there is an...

  11. CHAPTER NINE Language and Brain Evolution
    (pp. 232-272)

    Language is an essential facet of our shared humanity. At a basic level, we all know what language is and can appreciate its power and utility. Language requires no formal introduction. It is recognized as a cognitive tool, as the foundation of cultural unity and diversity, and as a critical feature that separates humans from other animals. The literature on language and languages is immense. It is a topic that has been addressed for centuries by intellectuals and others from every imaginable perspective. However, until 1967, the biology of language was a neglected topic, at least in terms of the...

  12. CHAPTER TEN Optimism and the Evolution of the Brain
    (pp. 273-280)

    I am optimistic about our ability to uncover the complex story of human brain evolution. Of course, such optimism may simply be the expression of a tendency toward “positive illusion,” a well-studied psychological phenomenon: “overly positive self-evaluations, exaggerated perceptions of control or mastery, and unrealistic optimism are characteristic of normal human thought” (Taylor and Brown 1988, p. 193). Although a strong connection with reality has long been thought to be necessary for mental health, it is quite clear that psychologically healthy people are actually those who can maintain a relatively sunny view of life—it motivates them to do productive...

  13. References
    (pp. 281-326)
  14. Acknowledgments
    (pp. 327-328)
  15. Index
    (pp. 329-338)