Seeing the Wood for the Trees: An Analysis of Evolutionary Diagrams in Biology Textbooks

Abstract

G raphical representations of evolutionary relation- ships among taxa have a long history in biology. The pervasive effect of two particularly influential representations, the "Chain of Being," rooted in the ideas of Plato and Aristotle, and the "Tree of Life," epitomized by Haeckel's trees of the late 1800s, can still be seen in contemporary representations. The Chain of Being encompasses the physical and metaphysical world in an unbroken chain that stretches from nonliving matter all the way to "supernatural" beings. It is possible to trace a connection from the Great Chain of Being depicted in Didacus Valades's 1579 Rhetorica Christiana (Lovejoy 1936), through Bonnet's (1745) scala naturae (scale of being) and Lamarck's (1809) extension of the "chain" in Philosophie Zoologique, to Haeckel's trees of the late 1800s. The Chain of Being and Tree of Life are founded on the concept of a linear evolutionary progression from simple to complex, with a distinctively teleological perspective. Although many other forms-both hierarchical and otherwise-have also appeared in the scientific press over the past 300 or so years, many current representations of evolution mirror the great chain as a process of orderly progression