The “March of Progress”, the iconic evolutionary image of an ancestral ape transforming into a proud, tool-wielding human, is not going anywhere. There is perhaps no other illustration that is as immediately recognizable as representing evolution, but the tragedy of this is that it conveys a view of life that does not resemble our present understanding of life’s history. Stephen Jay Gould addressed this two decades ago in his book Wonderful Life, in which he wrote;
Life is a copiously branching bush, continually pruned by the grim reaper of extinction, not a ladder of predictable progress. Most people may know this as a phrase to be uttered, but not as a concept brought into the deep interior of understanding. Hence we continually make errors inspired by unconscious allegiance to the ladder of progress, even when we explicitly deny such a superannuated view of life.
Yet the imagery is just too good to resist, and our continual desire to know whether this or that fossil was ancestral to another keeps us thinking in terms of evolutionary “ladders.” (A hominin clearly not ancestral to us such as Paranthropus robustus, for example, will never be as celebrated as one that might be closer to our ancestry.) The “March of Progress” is even more useful in terms of satire. What better way to show how backward or primitive your opponents are than to slot them early into the ape->human sequence or show them stamping in the opposite direction of “progress”?
Science historian Constance Areson Clark has recently reviewed the occurrence of this kind of imagery in a new paper published in the journal Isis entitled “‘You Are Here': Missing Links, Chains of Being, and the Language of Cartoons.” It is not just about the “March of Progress”, nor does it mention its modern manifestations, but Clark does provide a few examples of how evolution was depicted in a non-Darwinian fashion. As it turns out, the “March of Progress” has pretty deep roots.
Though the canonical “March of Progress” would not be published until 1965 in F. Clark Howell’s Early Man (a Time-Life book that I had in my little library as a child) the suggestion that evolution was linear appears in much earlier illustrations. As Clark points out, one of the most famous is a Punch cartoon (see above) showing life literally progressing from chaos to Charles Darwin. It was arranged in a circle, but it still carried a straight-line message which contrasted sharply with the branching pattern Darwin had envisioned.
Even more striking is one of the illustrations in T.H. Huxley’s popular pamphlet Man’s Place in Nature. It was not a cartoon, and so did not fall within the scope of Clark’s article, but her paper immediately made me think of it. From left to right it features the skeletons of a gibbon, orangutan, chimpanzee, gorilla, and human, with the Homo sapiens skeleton appearing to take a shaky step forward. Huxley, Darwin, and other evolutionists knew that humans did not evolve from living apes, and the illustration was probably intended to highlight the similarities and differences between the skeletons, but it still carried a glimmer of evolutionary progress since chimpanzees and gorilla’s were considered to be “man’s nearest allies.” (Though there is more to this statement than might be supposed, and does not anticipate our current understanding of how we are related to living apes.)
As scientists debated the mechanism of evolution during the late 19th and early 20th centuries such imagery fit well into notions of evolution heading towards a particular end point. This was especially prevalent in human evolution, where the evolution of our species was often treated as if it were an inevitable event. More than that, it could be suggested that humans were “more evolved” than other creatures.
This feeling of evolutionary superiority can be seen in a cartoon printed during the summer of the famous “Scopes Trial” entitled “The Upstart.” In it a motley crew of animals (including what one can only suppose it meant to be a dinosaur) stare slack-jawed as a young ancestral ape trots off to greet its evolutionary destiny. The meaning is that only humans have truly recognized their evolutionary potential, and it is our recent evolutionary past that separates us from all other animals. At the same time many cartoons featured religious fundamentalists, most often anti-evolution spokesman William Jennings Bryan, as being a “missing link” between apes and “higher” humans.
The “March of Progress” as it appeared during the 1960’s, then, was not so much a novel image as a particularly well-known example of scientific and satirical imagery that had been around for over a century. Though it can be aggravating, it is not surprising that it is still with us. It appears to speak to the heart of evolution, that “life changes over time”, yet this overly generalized view of evolution does not tell us about the way the evolutionary process works or the pattern it leaves behind. Like the term “missing link”, it is recognized as representing evolution, yet just what sort of evolution that might be is left open to interpretation.