Page - 58 - in JRFM - Journal Religion Film Media, Volume 03/02

58 | Larissa Carneiro www.jrfm.eu 2017, 3/2, 53–64 successful visual devices for promoting evolution and the idea that humans evolved from apes. The image also relies on a tradition of rhetorical figuration in order to make its claim persuasive, in employing incrementum. in this image, published in the History of Primates by sir Wilfred Le Gros Clarke (1949), six an- cestors line up as if marching toward progress from left to right. fahnestock explains that in this kind of visual representation, the image “has to be formed according to some principle of ordering, and by far the most common principle of ordering is by increase or decrease in some quantifier of attribute”.13 in such a rhetorical device, the argument is formed by a visual or textual sequence of things or events. Because of its sequential property, representing a linear pro- gression, this technique for scientific reasoning is perhaps one of the most com- mon strategies for evolutionary claims and, therefore, very present in textbook illustrations and museum exhibits, in which images or objects are arranged in a way that creates the perception of a clear movement from beginning to end. another important visual incrementum employed by the evolutionary per- spective is the paleontological timeline: a vertical system of chronological measurements accepted worldwide that relates fossils and stratigraphy to time. fahnestock cites as a famous sequence the progenitors of the modern horse crafted by paleontologist George Gaylord simpson. the chart presents a linear progression of “typical horses” associated with fossil deposits. individual strata register successive periods of time, with the upper stratum typically indi- cating younger or more recent life forms than those below it.14 ironically, this form of visual composition actually distorts what is currently accepted in evolutionary theory. stephen Jay Gould pointed out that this kind of linear representation of evolution is not accurate; indeed, he called it “em- barrassing”. the image suggests that evolution can be described as a steady, linear progress. But this misses the rhetorical point. as previously suggested by Law, these images accomplish their mission of simplification. They convert a much more complex branching perspective into a clear progression.15 But fahnestock is not the only scholar to suggest that darwin and later evo- lutionists relied on visual rhetorical strategies to convince readers of the plau- sibility of the theory. in 1990, the rhetorician John angus Campbell published the article “Scientific Discovery and Rhetorical Invention: The Path of Darwin’s Origin”, which became a seminal work in the field of rhetoric of science. In his essay, Campbell provocatively contended that darwin had not formulated the major aspects of his theory based on material evidence. By analyzing Darwin’s diaries and notebooks, Campbell concluded that each of darwin’s theories ex- plained reproduction, geological change, and natural selection only in rhetori- 13 fahnestock 1999, 95. 14 ibid., 100. 15 Gould 1989, 31–35.