Rhetorical and demonstrative modes of visual argument: looking at images of human evolution.

• Author: Shelley, Cameron
• Position: Special Issue: Visual Argument-Part 2

INTRODUCTION

Visual argumentation is pervasive in modern life (Fox, 1994). This is true not only in the public forum, in which visual display is used to persuade people to buy an advertiser's products or subscribe to a propagandist's point of view, but also in the scientific community, in which visual display is used to illustrate inferences or to communicate ideas to the general public. In both cases, the visual medium may be employed in more than one way to achieve whatever communication is desired.

For example, advertisements typically present certain visual images that are meant to persuade consumers to buy certain products. The persuasion may be brought about by the arguments visually embodied by the images. Consider the statement from the Shanghai Liberation Daily (6 May 1996), which verbalizes the argument contained in many ads currently directed towards new Chinese consumers:

Advertisements featuring blonde-haired blue-eyed people increase every day, as if a product which has been accepted by foreigners must be good. (Reuters, 7 May 1996)

Visual arguments are useful for their ease of comprehension and their emotional impact on the viewer, a fact which motivated the complaint just quoted. These qualities also motivate the use of visual argument in scientific discourse (see Myers, 1988) - compare the statement just quoted with the observation of Gifford-Gonzalez (1993, p. 31) regarding the portrayal of men and women in depictions of Paleolithic life:

Fully 84% of the pictures [examined] include adult males, while under half show women, 43% contain children, and 18% portray elders. . . . The cumulative message appears to be that where adult men aggregate and act is worth viewing, and those places where they do not may be overlooked.

Visual arguments of this kind may also be conveyed by single images. Consider the picture of Pithecanthropus alalus shown in Figure 1. These engaging creatures were posited by prominent German evolutionist Ernst Haeckel as an intermediate stage between "man-apes" and modern humans. Haeckel (1911, p. 726) had no fossil evidence for them, but relied on his famous evolutionary principle that "ontogeny recapitulates phylogeny" - that is, that the development of an organism from embryo to adult closely resembles the evolution of its ancestors from single-celled creatures to the present. Therefore, because human infants go through a stage in which they acquire the advanced trait of walking upright before they learn to speak, there must have been a recent human ancestor that could walk but not talk (Pithecanthropus alalus = non-speaking ape-man). This conclusion is made plausible and concrete by the representation of several of these premises in the figure: both adult individuals are small and pudgy, like modern infants, while the male on the right is leaning against a tree rather as a modern infant would lean on a table while learning to walk. Also, the portrayed individuals look as though they have something they want to say, but can't quite get it out, thus justifying Haeckel's nomenclature and evolutionary principle. Verbal knowledge of Haeckel's theory is necessary for the viewer to grasp the argument conveyed by this illustration. This representational strategy, in which visual and verbal forms of argument interpenetrate, may be termed the rhetorical mode of visual argument (cf. Groarke, in press).

Some visual arguments in scientific, and other, areas of discourse require a different mode of visual presentation. For example, it is sometimes necessary to convince the reader of a paleontology article that a fossil skeleton should be reconstructed according to one pattern and not another. An illustration can be the most efficient and convincing means of doing so because the process of skeletal reconstruction is more easily demonstrated visually than it is described verbally. This is an important contrast to the visual rhetorical mode of argument mentioned above. Rather than appealing to a mix of visual and verbal information, such illustrations approximate the argument itself as it might originally have been conceived by the scientist. Visual mental imagery (the "mind's eye") is a common vehicle of scientific inference, e.g., the formation of hypotheses (Shelley, 1996). Thus, some illustrations used in scientific literature may be seen primarily as demonstrations or portrayals of inferences made in the mind's eye. This representational strategy may be termed the demonstrative mode of visual argument.

The extent to which a visual argument is understood as rhetorical rather than demonstrative depends on the extent to which it appeals to the viewer's verbal knowledge and experience. But, like any extended text, one picture may convey more than one argument, and those arguments may themselves be either rhetorical or demonstrative in nature. In other words, rhetorical and demonstrative arguments may be found combined in a single image. One such case is the well-known March of progress, which purports to show the evolutionary progress from monkey to man. Modern evolutionary theory disposes of the notion of progress as it is embodied in the march, which means that the argument presented in the picture leads to a false conclusion. This paper shows that the march uses a combined mode of visual argument, and that this composite argument strongly implies the view of evolutionary change as progress.

This paper develops the distinction between rhetorical and demonstrative modes of visual argument as exemplified by pictorial views from human evolution. For the present, this distinction is characterized by diagnostic rules of thumb rather than by rigorous definition. Further work is needed to provide a comprehensive definition of each mode, to identify further modes or sub-modes of visual argument, and to extend this analysis to other domains of discourse.

THE RHETORICAL MODE

The rhetorical mode of visual argument is distinguished by a number of properties, such as its closeness to informal verbal arguments. Recent work on visual argument explores and characterizes this conceptual proximity (Groarke, in press). There exist visual forms of argument that closely resemble informal arguments such as the slippery slope, guilt by association, and the strawman, although the visual medium may also facilitate argumentative patterns that do not have a common verbal analog.

The correspondence between rhetorical visual argument and informal verbal argument depends importantly on the fact that the elements of pictures can individually encode or represent the premises of a verbal argument (Blair, this issue). Taken together, such premises then imply a conclusion of which the viewer is to be convinced. This kind of presentation is common enough in advertisements and editorial cartoons, but it is also apparent in scientific domains, such as paleoanthropology (Gifford-Gonzalez, 1993; Wiber, 1994). Visual argument is, for example, evident in a longstanding debate within paleoanthropology over the nature of Neandertals. As a whole, the debate concerns the detailed interpretation of Neandertal material remains (fossil skeletons, tools, burials, etc.) and what may be inferred from them. But the debate has also centered on the relation between the Neandertals and modern humans. Crudely put, the question is: Were the Neandertals intelligent and noble like modern humans or were they nasty and brutish like apes? Anthropologists have often made use of artwork to argue one way or the other on this question (see Moser, 1992; Trinkaus and Shipman, 1993). Two illustrations, produced early in this century by advocates of opposing positions, typify the nature of this debate. The first illustration, published in 1909 with the work of anthropologist Marcellin Bottle, argues for the apish position. It is reproduced in Figure 2. The message delivered by this picture is quite clear: Neandertals were essentially bipedal apes, brawny, not brainy. Several elements presented in the picture suggest this conclusion. For convenience, these elements may be divided into four categories: (1) the physical attributes of the Neandertal, (2) his material effects, tools, etc., (3) his activities and environment, and (4) the picture's aesthetic qualities.

Physical Attributes

The original caption under Kupka's picture claims that it depicts the original owner of the Correze fossil "recognising to the full the laws of anatomy." The physical attributes of Boule's Neandertal give it a distinctly primitive appearance. It is depicted as extremely hairy, having a stooped posture, bent knees, a forward-thrust head, and a protruding face. Each of these features is considered a diagnostic attribute of species membership by paleoanthropologists (although hair is essentially untraceable in archaeological remains). Modern humans are distinguished as a species by the absence of most body hair, an upright posture with straight knees, a head poised directly above the shoulders, and a flattened face framed by a vertical forehead and a prominent chin. The toes on the Neandertal's feet are also pictured as long and uneven in length, a characteristic of apes, rather than as short and arranged in a row, a characteristic of modern humans. The Neandertal is also given a set of gorilla-like fangs, as opposed to the modest canines present in modern man.

These anatomical details have been emphasized to set as much taxonomic distance between Neandertals and modern humans as possible, with special attention paid to the details that Boule's colleagues would recognize as relevant for this purpose (see also Shreeve, 1995, pp. 36-40). Several features have been unjustly exaggerated, such as the forward projection of the head, the presence of fangs, and the unusual structure of the toes (Trinkaus and Shipman, 1993, pp. 401-403). Others are better justified by the Chapelle-aux-Saints fossil, such as the large brow ridges, sloping forehead, and receding chin. The...