No. This is a wrong assumption. The famous illustration that is over 150 years old has only generated misconceptions about the origin of human beings. It is one of the most intriguing and deceptive drawings in the modern history of science . We explain it.
Evolution explains how all living things arose, including us humans. Although it is easier to assume that evolution works by continually adding characteristics or improvements to organisms, constantly increasing their complexity, such as that some fish developed legs and walked towards land, evolution is a much more complex process, since many branches of the tree of life has been kept in its most basic essence, like bacteria, or even reduced in complexity, like parasites.
Evolution does not follow a straight path
In fact, a recent study published in the journal Nature Ecology and Evolution , compared the complete genomes of more than 100 organisms (mostly animals), to study how the animal kingdom has evolved at the genetic level. The results show that the origins of the main groups of animals, such as that comprising humans, are not related to the addition of new genes, but to massive gene losses.
If evolution does not follow a straight, predetermined path, why have we seen these illustrations in museums and books ad nauseam, drawing a linear progression from primitive to modern? These images misrepresent how evolution really works. Let’s see where this misunderstanding comes from.
The source of the error
It is a holdover from before 1859, the year Charles Darwin first published his scientific theory of evolution through natural selection in “The Origin of Species.” Until then, the traditional view of how the world was organized was through a kind of hierarchy towards perfection : all beings on earth, animate and inanimate, could be organized according to an increasing scale of perfection starting from the mushrooms, for example, in the lowest echelon, all the way to human beings at the top.
In this view, nature is hierarchically organized . The organization goes from the simple to the perfect . And, furthermore, it assumes that there are no intermediate stages between the levels of this hierarchy.
Darwin’s book contained only one illustration: a tree diagram that represented evolution as a complex process characterized by random events, which is roughly how scientists view evolution today.
And the image that we all know?
The first version of the classical image appeared in an 1863 book by the English comparative anatomist Thomas H. Huxley, and it recalled an older tradition that presented nature as a “chain of being.” Combining aspects of the new scientific theory with a way of thinking apt for the Victorians of the time, he suggested a logical and uniform progression that eventually reached the final species of evolution: Homo sapiens.
But we have already clarified that evolution does not work that way, as Darwin himself had made clear. It is aimless, not regular, or straight, leaves many species in the way, and does not always lead to greater complexity. Life, as such, is not predictable at all. And it keeps evolving.
Why has this misleading image prevailed?
Although it is a fiasco on a scientific level, the image has been a great success with the public, forever. If we take a look at the multiple ways in which the image has been used over time (whether as a joke, as a comment, in the form of scientific fact …) it offers an idea that evidences the desire of a society that struggles to understand evolution and what it means to be human.
Referencia: Guijarro-Clarke, C., Holland, P.W.H. & Paps, J. Widespread patterns of gene loss in the evolution of the animal kingdom. Nat Ecol Evol 4, 519–523 (2020). https://doi.org/10.1038/s41559-020-1129-2
