“The bush is not a failure. It is a garden. And gardens grow best when we dance.” 

By Andrew Klein

Dedication: To my wife – who taught me that life is not a ladder to be climbed, but a dance to be joined.

For generations, the public has been taught a simple, seductive story. Evolution, we are told, is a ladder. Primitive forms at the bottom. Complex forms at the top. And at the summit, triumphant and alone, stands Homo sapiens. The famous “March of Progress” – a straight line of stooped ape ancestors rising into proud, tool‑wielding humans – has become the universal icon of evolution.

The only problem is that it is spectacularly wrong.

“Life is a copiously branching bush, continually pruned by the grim reaper of extinction, not a ladder of predictable progress.” – Stephen Jay Gould

The ladder is a relic of pre‑Darwinian theology. It is the scala naturae – the “great chain of being” – in which all creatures are arranged in a single, hierarchical line from the lowest worm to the highest angel, with humans just below the divine. That view was popular among naturalists until the mid‑19th century. Darwin himself was still influenced by “ladder thinking”, and the linear iconography persists today, perpetuating a fundamental misunderstanding of how life actually changes.

When we look at the fossil record without the ladder, a very different picture emerges: a bush. A tangled, branching, chaotic shrub of life, in which most twigs are dead ends and every surviving lineage is a cousin, not a descendant.

This is not a failure of evolution. It is the truth.

The Missing Link That Was Never Missing

The search for “missing links” is a symptom of ladder thinking. The phrase itself is misleading: scientists prefer “transitional fossil”, and they have found thousands of them. The first famous example was Archaeopteryx, the feathered dinosaur discovered in 1861, which beautifully bridged the gap between reptiles and birds. Yet every such discovery does not “fill” a gap; it creates two new gaps – what came before, and what came after.

The gaps are not a problem. They are a feature of the bush.

A 2008 study in BioEssays called this the “primitive lineage fallacy” – the mistaken assumption that species‑poor lineages that appear early in a phylogeny are ancestral to later, more diverse groups. In reality, a modern phylogeny shows relationships among evolutionary cousins, not a unilinear progression from “primitive” to “advanced”.

The ladder metaphor is so persistent because it is psychologically comfortable. It tells a story with a clear hero – us – and a clear direction: up. But as the evolutionary biologist David Archibald has noted, the ladder of progress is “Steve Gould’s Bane” – the most persistent and damaging myth in popular evolution.

Punctuated Equilibrium: The Tempo of the Dance

In 1972, Stephen Jay Gould and Niles Eldredge proposed a radically different tempo for evolution: punctuated equilibrium. They argued that most species, during their geological history, either do not change in any appreciable way or fluctuate mildly in morphology, with no apparent direction. Evolutionary change is concentrated in very rapid events of speciation – geologically instantaneous, even if continuous in ecological time.

“Evolutionary trends are not the product of slow, directional transformation within lineages; they represent the differential success of certain species within a clade.”

This is not a ladder. It is a dance. Long periods of stability punctuated by bursts of creativity. The tree of horses, once much more diverse than the single surviving genus Equus, is not a straight line from Hyracotherium to the modern horse; it is a “twisted and tortuous excursion from one branch to another”. We can draw a pathway from a common beginning to a lone surviving twig – but that pathway is not a ladder. It is a braid.

Co‑Evolution: The Dance Partners

The bush is not silent. It is full of relationship.

Co‑evolution is the process by which two or more species reciprocally affect each other’s evolution. It is a dance of mutual adaptation, and it is the hidden engine of the bush.

The classic example is the co‑evolution of grasses and grazers. Grasses evolved sod‑growth and abrasive leaves to cope with the hard hooves and high‑crowned teeth of grazing mammals. In response, the grazers evolved ever more efficient digestive systems. Neither would exist without the other. The result, over the past 30 million years, was the creation of an entirely new ecosystem – the grasslands – which transformed the planet’s carbon cycle, water balance, and even its climate.

This is not competition. It is collaboration.

Another example, just published in June 2026, is the discovery of a new microraptor dinosaur, Jian changmaensis, from the Cretaceous of China. This “four‑winged” dinosaur had long feathers on both its arms and legs, allowing it to glide between trees like a flying squirrel. It lived in a lakeside forest teeming with early birds. In the same fossil beds, researchers have found hundreds of bird fossils – and broken bird bones that look exactly like the pellets coughed up by modern owls. The most likely interpretation is that Jian changmaensis was hunting those birds.

The dinosaur and the bird were not on a ladder. They were dancing. One evolved feathers for gliding; the other evolved faster flight. Each was a selection pressure on the other. Neither was “more evolved”. They were simply co‑evolving.

The Myth of the Lone Ancestor

The ladder metaphor encourages a search for the one true ancestor – the single fossil that “proves” a linear chain. But in the bush, there is no such thing.

The evolution of flight did not happen in a straight line. Feathers appeared millions of years before flight, serving first in thermal insulation, then in display, then in gliding, then in powered flight. The four‑winged microraptors are not our ancestors; they are our cousins. They are a twig on the bush, not a rung on a ladder.

The same is true of human evolution. Australopithecus did not “turn into” Homo. The human bush was once full of multiple coexisting hominin species – Paranthropus, Homo habilis, Homo erectus, Homo floresiensis – living alongside one another. Some went extinct. One survived. That is not a ladder. It is a pruning.

Gould expressed this perfectly: “Homo sapiens is but a tiny, late‑arising twig on life’s enormously arborescent bush – a small bud that would almost surely not appear a second time.”

The Tools We Use Shape What We See

Why does the ladder persist? Partly because it is easy to draw. Partly because it flatters our ego. But also because the tools we use shape the questions we ask.

A 2008 study in BioEssays warned that reading phylogenetic trees as ladders from left to right leads to the “primitive lineage fallacy” – the mistaken inference that early‑branching lineages are ancestral to later ones. This fallacy is baked into much of the software, the textbooks, and the media coverage of palaeontology.

The “March of Progress” has deep roots in Western thought, going back to Aristotle’s scala naturae. As the science historian Constance Clark has shown, even Darwin’s contemporaries struggled to escape the linear imagination, and the ladder persists in cartoons, advertisements, and popular culture to this day.

But if we change our tools – if we draw the trees as bushes, if we emphasise cousin relationships rather than ancestral–descendant chains – the entire picture changes. Suddenly the dead ends are not failures; they are successful experiments. The survivors are not “more evolved”; they are simply lucky. And the process is not a goal‑directed march; it is a dance with no final pose.

Conclusion: In Co‑Evolution, the Only Ancestors Who Matter Are Those Who Danced Successfully

The ladder is a lie. The bush is true.

And the bush is not a static collection of species; it is a dynamic network of relationships. Every interaction – predator‑prey, plant‑herbivore, host‑parasite – is a selection pressure. Every adaptation is a response to a partner’s move. This is co‑evolution, and it is the fundamental process of life.

The “missing link” is missing only from the ladder. In the bush, there are no missing links – only cousins who danced, succeeded, failed, and left traces in the rocks.

We are not the destination of evolution. We are a twig – a late‑arising, fragile, contingent twig. Our survival is not guaranteed. Our past is not a straight line. And our future depends not on climbing a ladder, but on learning to dance.

So let us abandon the ladder. Let us embrace the bush. Let us look at the microraptor and the bird, at the grass and the grazer, at the human and the hominin – and see not a race, but a dance.

Because in co‑evolution, the only ancestors who matter are those who danced successfully.

Andrew Klein

References

1. Jenner, R. A. (2017). Evolution is Linear: Debunking Life’s Little Joke. Natural History Museum, London.

2. Gould, S. J. (1991). Bully for Brontosaurus. W. W. Norton.

3. Gould, S. J., & Eldredge, N. (1972). Punctuated equilibria: the tempo and mode of evolution reconsidered. Paleobiology.

4. Omland, K. E., Cook, L. G., & Crisp, M. D. (2008). Tree thinking for all biology: the problem with reading phylogenies as ladders of progress. BioEssays.

5. National Geographic. (2009). The March of Progress Has Deep Roots.

6. Lamanna, M. et al. (2026). Jian changmaensis – a new microraptor from the Changma Basin, China. Annals of Carnegie Museum.

7. Retallack, G. J. (2014). Coevolution of Life and Earth. In Treatise on Geochemistry (2nd ed.). Elsevier.

8. Clark, C. A. (2010). “You Are Here”: Missing Links, Chains of Being, and the Language of Cartoons. Isis.

9. Archibald, D. (2005). The Ladder of Progress – Steve Gould’s Bane.

10. Bateman, C. (2012). The Mythology of Evolution. Zero Books.

11. Bryson, B. (2003). A Short History of Nearly Everything. Broadway Books.

12. Zimmer, C. (2001). Evolution: The Triumph of an Idea. HarperCollins.