Wonderful Life: The Burgess Shale and the Nature of History Read Online Free PDF Page A

discuss the origin of this model in Haeckel’s original trees and their influence upon Walcott’s great error in reconstructing the Burgess fauna.) All these trees show the same pattern: branches grow ever upward and outward, splitting from time to time. If some early lineages die, later gains soon overbalance these losses. Early deaths can eliminate only small branches near the central trunk. Evolution unfolds as though the tree were growing up a funnel, always filling the continually expanding cone of possibilities..
    In its conventional interpretation, the cone of diversity propagates an interesting conflation of meanings. The horizontal dimension shows diversity—fishes plus insects plus snails plus starfishes at the top take up much more lateral room than just flatworms at the bottom. But what does the vertical dimension represent? In a literal reading, up and down should record only younger and older in geological time: organisms at the neck of the funnel are ancient; those at the lip, recent. But we also read upward movement as simple to complex, or primitive to advanced. Placement in time is conflated with judgment of worth .
    Our ordinary discourse about animals follows this iconography. Nature’s theme is diversity. We live surrounded by coeval twigs of life’s tree. In Darwin’s world, all (as survivors in a tough game) have some claim to equal status. Why, then, do we usually choose to construct a ranking of implied worth (by assumed complexity, or relative nearness to humans, for example)? In a review of a book on courtship in the animal kingdom, Jonathan Weiner ( New York Times Book Review , March 27, 1988) describes the author’s scheme of organization: “Working in loosely evolutionary order, Mr. Walters begins with horseshoe crabs, which have been meeting and mating on dark beaches in synchrony with tide and moon for 200 million years.” Later chapters make the “long evolutionary leap to the antics of the pygmy chimpanzee.” Why is this sequence called “evolutionary order”? Anatomically complex horseshoe crabs are not ancestral to vertebrates; the two phyla, Arthropoda and Chordata, have been separate from the very first records of multicellular life.

    1.16. The iconography of the cone of increasing diversity, as seen in six examples from textbooks. All these diagrams are presented as simple objective portrayals of evolution; none are explicit representations of diversification as opposed to some other evolutionary process. Three abstract examples (A–C) are followed by conventional views of three specific phylogenies–vertebrate (D), arthropod (E), and mammalian (F, on p. 42). The data of the Burgess Shale falsify this central view of arthropod evolution as a continuous process of increasing diversification.

    1.16 A conventional view of mammalian phylogeny.
    In another recent example, showing that this error infests technical as well as lay discourse, an editorial in Science , the leading scientific journal in America, constructs an order every bit as motley and senseless as White’s “regular gradation” (see figure 1.3). Commenting on species commonly used for laboratory work, the editors discuss the “middle range” between unicellular creatures and guess who at the apex: “Higher on the evolutionary ladder,” we learn, “the nematode, the fly and the frog have the advantage of complexity beyond the single cell, but represent far simpler species than mammals” (June 10, 1988).
    The fatuous idea of a single order amidst the multifarious diversity of modern life flows from our conventional iconographies and the prejudices that nurture them—the ladder of life and the cone of increasing diversity. By the ladder, horseshoe crabs are judged as simple; by the cone, they are deemed old. * And one implies the other under the grand conflation discussed above—down on the ladder also means old, while low on the cone denotes simple.
    I don’t think that any particular secret, mystery,