Evolution, regarded as “both a fact and a theory”, is one of the most fundamental concepts of modern science. Yet, animal researchers implicitly refute it each and every time they force a nonhuman animal to serve as a “model” for humans.

Animal research has historically rejected the principles of evolution, basing itself instead on unproven – and even disproven! – ideas.

Opening the history books, we once again find ourselves face-to-face with 19th-century vivisector Claude Bernard, who put us on the course to modern animal research. He did this in large part by convincing the scientific community of several falsehoods, including that “if any disease could not be reproduced in animals in the laboratory, it simply did not exist–despite accumulated clinical (human) data to the contrary”. Critically, Bernard also rejected evolutionary theory as speculative and unscientific – not for a lack of evidence, but because it  threatened “the control, the immediacy, the prestige, and the money” he derived from animal research. 

To justify his prolific “dismantling of [animals] organ by organ”, Bernard argued that humans and nonhuman animals differ only in measurable – or quantitative – ways (like, e.g., body weight), such that nonhuman animals could serve as “stand-ins” for humans in experiments. He famously told his students “‘Why think when you can experiment?’” and taught that “[o]nce an experiment is true . . . it is always true; it cannot be true for a mouse, and not true for a donkey or a human being.” This unfounded belief in the “interchangeability of species” became a cornerstone of animal research.

However, evolutionary theory disproved Bernard’s claims almost, if not actually, from their inception. Evolution reveals that humans and nonhuman animals differ qualitatively – through complex adaptations in biology and behavior – and that even small evolutionary differences between species can cause drastically different responses to the same stimulus. This means that nonhuman animals cannot serve as “stand-ins” for humans because one species cannot reliably predict outcomes in another. Yet, animal researchers continue to claim otherwise, perpetuating Bernard’s devastating, unscientific legacy. 

When animal researchers began referencing the theory of evolution, they did so selectively and misleadingly.

As evolutionary theory gained acceptance, some researchers pivoted from outright rejection of it to cherry-picking aspects that justified their experiments. They leaned on Darwin’s principle of homology – the idea that humans and nonhumans share a common ancestry – to argue that findings in nonhuman animals could apply to humans. However, they simultaneously ignored Darwin’s emphasis on the uniqueness of each species because this “undermine[d]” their position. 

This cherry-picked hypothesis – that similarities between species make nonhuman animals reliable “models” for humans – has “been repeatedly tested and disproven”. Contrarily, tested and proven evolutionary theory has shown that, while species may share biological traits, they also have significant biological differences; and these differences, rooted in millions of years of evolutionary divergence, often lead to drastically different responses to the same stimuli.

Experts agree that the theory of evolution not only undermines the premise of animal research but also explains its failures to provide reliable results for humans. 

Say they:

• Evolution “shows us why using animals as predictive models for human drug and disease response is a scientifically invalid modality.”
• “Species differences undermine the whole premise of animal research that is intended to have relevance to humans. It is the paradigm’s fatal flaw, not an issue that can be overcome.”
• The theory of evolution “account[s] for the failures of animal experimentation” – “animals are not defective first drafts of humans” and, therefore, “unlikely test beds for human medicine”. 
• “The theory of evolution, and our present understanding of tissue and cellular evolutionary speciation, casts decisive doubt on the continuing efficacy of the animal model.”
• “ . . . the theory that explains why animal tests are unable to reliably predict outcomes in humans is, as we know, evolutionary theory.”
• “ . . . the Theory of Evolution provides us a theoretical framework while advancements in genetic and molecular biology provide the empirical data as to why animals cannot adequately predict human drug and disease response. Mice are unique and interesting creatures in their own right, they are not simply men writ small!”

In sum, experts agree that – far from supporting animal research – evolutionary theory reveals why animal research findings consistently fail to translate to humans and explains that, no matter animal researchers’ claims, animals are not interchangeable beings. 

At the same time, animal researchers have no theory that explains why animal research should reliably or consistently translate to humans.

Animal researchers have not – and cannot – offer a scientific theory that supports their use of nonhuman animals as “models” for humans; and their frequent failures only emphasize this lack of foundation. 

Writes scientist Pandora Pound:

If the animal research paradigm were undergirded by a robust underlying theory, animal experiments would be associated with medical advances consistently and reliably. In the absence of theory, however, we find ourselves on shaky ground. As philosophers Hugh LaFollette and Niall Shanks write, ‘isolated examples explain or illuminate nothing. They become significant only in the context of well-confirmed scientific theories – theories such as evolutionary biology – which shape the way we conceptualize evidence. If the cases selected by animal research to demonstrate the value of their work were explained by a unifying theory, their arguments would be stronger. But no such explanatory theory exists. Indeed, the examples of failure selected by those opposing animal research are on firmer footing because they can be unified and explained by evolutionary theory . . . 

Evolutionary theory doesn’t just undercut the supposed “science” behind animal research; it also challenges the discriminatory belief system that perpetuates it.

Animal research is made possible by speciesism, which can be described as the “idea that humans are fundamentally different from and superior to animals”. 

Evolutionary theory shatters this notion, proving that there are no categorical hierarchies in nature; recognizing that all species are “equally ideal, equally successful”; and teaching that the “similarities and contrasts among species are nuances or shades of gray, not stark black-and-white differences”.

So, as animal researchers continue to deny evolution to justify their careers, we who seek a just world can evolve without them by fighting to end vivisection. 

Because we believe this truth:

It is a matter of evolution in human ethics and consciousness when citizens oppose the practices of forcibly restraining, isolating, shocking, addicting to drugs, starving, infecting, burning, poisoning, brain damaging, blinding, and genetically manipulating other sentient beings, regardless of any noble goal claimed behind the practices.

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