Convergent Evolution

Convergent Evolution: Limited Forms Most Beautiful

George R. McGhee
Copyright Date: 2011
Published by: MIT Press
Pages: 336
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  • Book Info
    Convergent Evolution
    Book Description:

    Charles Darwin famously concluded On the Origin of Species with a vision of "endless forms most beautiful" continually evolving. More than 150 years later many evolutionary biologists see not endless forms but the same, or very similar, forms evolving repeatedly in many independent species lineages. A porpoise's fishlike fins, for example, are not inherited from fish ancestors but are independently derived convergent traits. In this book, George McGhee describes the ubiquity of the phenomenon of convergent evolution and connects it directly to the concept of evolutionary constraint--the idea that the number of evolutionary pathways available to life are not endless, but quite limited. Convergent evolution occurs on all levels, from tiny organic molecules to entire ecosystems of species. McGhee demonstrates its ubiquity in animals, both herbivore and carnivore; in plants; in ecosystems; in molecules, including DNA, proteins, and enzymes; and even in minds, describing problem-solving behavior and group behavior as the products of convergence. For each species example, he provides an abbreviated list of the major nodes in its phylogenetic classification, allowing the reader to see the evolutionary relationship of a group of species that have independently evolved a similar trait by convergent evolution. McGhee analyzes the role of functional and developmental constraints in producing convergent evolution, and considers the scientific and philosophical implications of convergent evolution for the predictability of the evolutionary process.

    eISBN: 978-0-262-29887-2
    Subjects: Ecology & Evolutionary Biology, Biological Sciences

Table of Contents

  1. Front Matter
    (pp. i-vi)
  2. Table of Contents
    (pp. vii-viii)
  3. Series Foreword
    (pp. ix-x)
    Gerd B. Müller, Günter P. Wagner and Werner Callebaut

    Biology is becoming the leading science in this century. As in all other sciences, progress in biology depends on interactions between empirical research, theory building, and modeling. But whereas the techniques and methods of descriptive and experimental biology have evolved dramatically in recent years, generating a flood of highly detailed empirical data, the integration of these results into useful theoretical frameworks has lagged behind. Driven largely by pragmatic and technical considerations, research in biology continues to be less guided by theory than seems indicated. By promoting the formulation and discussion of new theoretical concepts in the bio-sciences, this series intends...

  4. Preface: Limited Forms Most Beautiful
    (pp. xi-xii)
  5. 1 What Is Convergent Evolution?
    (pp. 1-12)

    A porpoise looks like a fish. It has a fusiform, streamlined body like that of a swordfish or a tuna. It has four fins on the ventral side of its body, instead of four legs. It has a large fin at its posterior end, instead of a tail. And it even has a vertical fin centered on its back, so it looks very much like a shark when it is swimming through the water toward you.

    Astonishingly, all appearances to the contrary, a porpoise is not a fish; it is a mammal. It possesses all the distinctive combination of mammalian...

  6. 2 Convergent Animals
    (pp. 13-92)

    Some of the most spectacular examples of convergent evolution are clearly due to the functional constraints of locomotion. Consider one of the most frequently cited cases of convergent evolution: the astonishing morphological similarity between the extinct Mesozoic marine reptileIchthyosaurus platyodonand the living marine mammalPhocaena phocaena, the harbor porpoise, orTursiops truncatus, the bottlenose dolphin. Not only do they look amazingly similar to one another, but they all look amazingly similar to large, fast-swimming fishes likeXiphias gladius, the swordfish, orCarcharodon carcharias, the great white shark. The cartilaginous fishes and the bony fishes both solved the physics...

  7. 3 Convergent Plants
    (pp. 93-134)

    The reverse of the old adage “not seeing the forest for the trees”—the condition in which people overlook a larger overall pattern because they are too narrowly focused on individual particulars—is “not seeing the trees for the forest.” The trees in a forest do vary—an oak tree is different from a maple tree—but the apparent similarity of tree form that can be seen throughout thousands of trees in a forest may give one the impression that all trees are variants of a single common ancestor. This is not so. Nine separate groups of plants have independently...

  8. 4 Convergent Ecosystems
    (pp. 135-176)

    Imagine a universe in which there are an unlimited number of ways to make a living. In such a universe, each species would have its own unique way of making a living, different from all other species. When we examine the ecological structure of living organisms on Earth, we can clearly see that we do not inhabit such a universe.

    In our universe the number of ways of making a living, of ecological roles or niches, is demonstrably limited. Multiple species are constrained in their evolution to playing the same ecological role, filling the same ecological niche, as best they...

  9. 5 Convergent Molecules
    (pp. 177-208)

    The source code for all life on Earth is contained in the deoxyribonucleic-acid molecule, DNA. DNA codes for RNA molecules, ribonucleic acids, and RNA codes for the assembly of amino acids into proteins, the building blocks of life. Each of the essential molecules of life has a finite number of possible states. Since DNA and RNA molecules contain only four different nucleotides, the code for Earth life is a base-four system. As such, the probability,p, of convergent molecular evolution of the same nucleotide at the same site in two different DNA or RNA molecules, via random mutation, is one...

  10. 6 Convergent Minds
    (pp. 209-244)

    How can minds be said to converge? We consider our mental states to be a function of our brain structures and sensory inputs. At first glance, then, organisms with radically different brain structures would be expected to have radically different minds. Take, for example, the brains of a magpie and a human. One is a bird brain, possessed by an avian dinosaur in the sauropsid clade of amniotes, and the other is a primate brain, possessed by a placental mammal in the synapsid clade of amniotes. The sauropsid and synapsid lineages diverged back in the Carboniferous, and have evolved along...

  11. 7 Functional and Developmental Constraint in Convergent Evolution
    (pp. 245-264)

    Albert Einstein once mused, “What really interests me is whether God could have made the world in a different way.” To Einstein, God represented the laws of nature. He was asking whether the evolution of the universe was so constrained by the initial conditions of the Big Bang, by the observed constants of nature, that only the present universe could have evolved? Or were alternative universes possible, universes that would have evolved along physical pathways not followed by our present universe?

    This question can be framed with respect to biological evolution as well. Is the evolution of life so constrained...

  12. 8 Philosophical Implications of Convergent Evolution
    (pp. 265-278)

    Most scientists tend to ignore philosophers. In evolutionary biology, the scientist Ernst Mayr (1964, xi–xii) traced this tendency back to Charles Darwin himself: “No one resented Darwin’s independence of thought more than the philosophers. How could anyone dare to change our concept of the universe and man’s position in it without arguing for or against Plato, for or against Descartes, for or against Kant? Darwin had violated all the rules of the game by placing his argument entirely outside the traditional framework of classical philosophical concepts and terminologies. . . . No other work advertised to the world the...

  13. Appendix: A Phylogenetic Classification of Life
    (pp. 279-286)
  14. References
    (pp. 287-302)
  15. Index of Common Names
    (pp. 303-308)
  16. Index of Species
    (pp. 309-318)
  17. Index of Topics
    (pp. 319-322)