Marching up the wrong tree

Before Darwin published his theory of evolution through natural selection, On the Origin of Species, evolution wasn’t a new concept. It had been discussed by many different people of science as early as the Ancient Greeks. It was how evolution happened that no one was able to explain satisfactory until Darwin (and Alfred Russel Wallace, who independently came to the similar theory). When it was published, it caused a huge stir. The Victorians couldn’t break away from their long-held beliefs that God had created ‘man’ in his image, and that humans were separate from the animal kingdom. Presenting this valid theory of evolution would sever the power of the Church, which at the time was the head of most things and most people.  In anticipation for backlash against Darwin, his close friend, Thomas Henry Huxley, wrote to him ‘I am sharpening up my claws and beak in readiness.’ 

I’m a little fan of Thomas Henry Huxley. Despite being well-known for his quick wit and sometimes fearsome demeanour, he was a loving family man, and a very good friend to those he liked. He wrote numerous natural history books, with the aim of making science accessible to the non-expert. One of these, Man’s Place in Nature (1863), focuses on human evolution and our common ancestor. In it, there is a famous illustration by Benjamin Waterhouse Hawkins, which shows the skeletons of a gibbon, orang-u-tan, chimpanzee, gorilla and human.

Tby Waterhouse Hawkins
Benjamin Waterhouse Hawkins illustration in Huxley’s Man’s Place in Nature. (Image Public Domain)

I’ve noticed that this illustration does looks rather similar to The March of Progress, an image that has fed to the misunderstanding of human evolution, and has been written about numerous times by many great science writers (including Stephen Jay Gould and Riley Black). Originally called The road to Homo sapiens, this iconic image was commissioned for Early Man, one of a series of books by Life-Time Books. It shows 15 extinct primates lined up from left to right as if one species evolves into the next. A ladder of human evolution, with the magnificent Homo sapiens at the very pinnacle. It is of course wrong. But that hasn’t stopped it being reused and rejigged for a myriad of different uses from advertising to prints on T-shirt. It is so popular and constantly used in mainstream media because it is so simple: one species evolves into another, better species: humans are at the end of this ‘progress’.

The March of Progress
The March of Progress, by Rudolph Zallinger. (Image Public Domain)

Some years ago, historian Jennifer Tucker suggests that the image from Man’s Place in Nature actually does indicate evolution, and highlights, the ‘chain of being’, which is a Christian thought of a hierarchical structure in nature, with minerals and plants under animals, and animals under humans, and humans being at the top, just below angels and God. The ‘chain of being’ was first thought of by Ancient Greek philosophers, and adapted in the Middle Ages to focus on God’s main creation: humans. Whilst there are similarities between Huxley’s skeletons and March of Progress, I can’t see it illustrating humans at the pinnacle of evolution: Huxley wasn’t one to jump onboard the Christian bandwagon, and he understood Darwin’s ideas well, having read proofs of his book and discussed them with him in letters and in person. The illustration was a comparison of the skeletons of apes, not an evolutionary diagram, and Huxley makes no reference to it being such in Man’s Place in Nature.

I wanted to find out if the March of Progress was inspired by this the Waterhouse Hawkins illustration. The art work was created by Rudolph Zallinger, who painted the beautiful Age of Reptiles mural at the Yale Peabody Museum. I contacted the museum at Yale to see if they knew any more about the March of Progress illustration, and I was introduced to Zallinger’s daughter, Lisa. Sadly we don’t know what inspired him: “…it is tough to say what my father actually drew from or referred to in order to depict that March. We do not know.”

But, Lisa gave a lot more information about the background into the development of this art. The illustrations were based on the science known at the time, as Lisa told me in an email: “…he consulted many of the prominent anthropologists and scientists at Yale for assistance. He was very keen on representing all we knew about the various [hominins]…both in terms of dating, which came before the other in the sequence, and in terms of the bones of each that had actually been recovered.”

Zallinger’s original ideas for illustrating for this Time-Life Book were very different to how they ended up: “His initial drawings were actually groupings of these bones, next to a representation of what that particular [hominin] might have looked like.” He worked with scientific colleagues to illustrate correctly the pose and posture of each one. The Editor for the Early Man book wasn’t keen on Zallinger’s ideas: “the editor did not believe that these depictions would be compelling or striking enough to excite the readers. It was the editors suggesting that they be depicted in a ‘March’.” But Zallinger wasn’t just an artist, he knew about evolution, and his illustrations were always based on the most up to date scientific knowledge of the time. “My father was not really keen on this portrayal, because he was already very aware that [hominin] evolution was more likely akin to the branching of a tree rather than a straight, linear march, so he resisted this depiction. The editor won out, however, and the iconic image was born.”

Discovering the background into how this renowned illustration was conceived is as fascinating as the art itself. Despite Zallinger working closely with artists, and having a good understanding of evolution, it was the need for something to excite readers, and something that would be visually easy to understand that won the day. This one decision has created perhaps the biggest, most dangerous, misunderstanding of evolution that has ever existed. In all its simplicity, it shows progress. An improvement from what came before. The idea that animals get better as they evolve is wrong. Every animal and plant alive today is just as evolved as each other. None is more ‘primitive’. None is ‘simple’. And certainly none are inferior to others. Each is specially adapted for their environment, some more specialist than others, and some more generalist.

Evolution is quite simple when you break it down. When an egg is fertilised, genes from the mother and father are passed on. Sometimes, small changes can happen where DNA doesn’t replicate exactly as it should have, and these may create new genes for new features (a slightly longer beak for example). If it is harmful, then the young animal won’t survive, and that trait is lost in the population. If it proves useful (a slightly longer beak could mean it can get food from a new place), this trait is passed down to the next generation, where eventually the whole population has it, and a new species is born. We can look at fossils, and even genetics, to see the evolution of species in the past. Humans are no different. Our species evolved around 300,000 years ago in Africa, and our family was once more diverse than you can imagine.

The many different species of humans going back 1 million years. Notice how there were several different species on our planet at once. (Image from Galway-Witham, Cole and Stringer, 2019)

There were dozens of different species of hominins (upright walking apes), many of which lived alongside others. It wasn’t a ladder with one species evolving straight into the next, it was a tree; a big, bushy tree. As small populations moved out and explored away from other populations, they adapted to the different environments. Small changes, passed down through their genes, allowed them to survive better in these new environments where they became a new species. It may be a little more complicated because some species were still mating and mixing genes, so anthropologist John Hawks says it was more like a big river delta.

We were never inevitable. Steven Jay Gould once wrote that if we were to go back to the beginning of life and start it all over, life today would be very different, and there would be no humans around. That’s a big thing to think about. We are not special. We are not better, or ‘higher’ than other animals. Evolution was not primed to make us here today. We are just here. Now. But, there is something special about us. We have the power to change our environment around us. Not just locally, but globally. Presently we are taking advantage of that environment, destroying it, and causing the extinction of countless species every year. Species that have evolved and adapted over millions of years. But, we can use that power, our understanding of our actions, to protect this beautiful, fragile planet we live on. There is no march of progress. There is no ‘road to Homo sapiens’. There is Earth, and the immeasurable different types of beautiful animals and plants that we share the planet with. 

Written by Jan Freedman (@JanFreedman)

Further reading:

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