During the 1920s and 1930s, many biologists questioned the viability of Darwin’s theory as a mechanism of evolutionary change. In the early 1940s, and only after a number of alternatives were suggested, Darwinists succeeded to establish natural selection and gene mutation as the main evolutionary mechanisms. While that move, today known as the neo-Darwinian synthesis, is taken as signalling a triumph of evolutionary theory, certain critical problems in evolution—in particular the evolution of animal function—could not be addressed with this approach. (...) Here I demonstrate this through reconstruction of the evolutionary theory of Joseph Needham (1900–1995), who pioneered the biochemical study of evolution and development. In order to address such problems, Needham employed Herbert Spencer’s principles of emergence and Ernst Haeckel’s theory of recapitulation. While Needham did not reject Darwinian theory, Spencerian and Haeckelian frameworks happened to better fit his findings and their evolutionary relevance. He believed selectionist and genetic approaches to be important but far from sufficient for explaining how evolutionary transformations occur. (shrink)

The "tree of life" iconography, representing the history of life, dates from at least the latter half of the 18th century, but evolution as the mechanism providing this bifurcating history of life did not appear until the early 19th century. There was also a shift from the straight line, scala naturae view of change in nature to a more bifurcating or tree-like view. Throughout the 19th century authors presented tree-like diagrams, some regarding the Deity as the mechanism of change while (...) others argued for evolution. Straight-line or anagenetic evolution and bifurcating or cladogenetic evolution are known in biology today, but are often misrepresented in popular culture, especially with anagenesis being confounded with scala naturae. Although well known in the mid 19th century, the geologist Edward Hitchcock has been forgotten as an early, if not the first author to publish a paleontologically based "tree of life" beginning in 1840 in the first edition of his popular general geology text Elementary Geology. At least 31 editions were published and those between 1840 and 1859 had this "paleontological chart" showing two trees, one for fossil and living plants and another for animals set within a context of geological time. Although the chart did not vary in later editions, the text explaining the chart did change to reflect newer ideas in paleontology and geology. Whereas Lamarck, Chambers, Bronn, Darwin, and Haeckel saw some form of transmutation as the mechanism that created their "trees of life," Hitchcock, like his contemporaries Agassiz and Miller, who also produced "trees of life," saw a deity as the agent of change. Through each edition of his book Hitchcock denounced the newer transmutationist hypotheses of Lamarck, then Chambers, and finally Darwin in an 1860 edition that no longer presented his tree-like "paleontological chart.". (shrink)