Deep in the human unconscious is a pervasive need for a logical universe that makes sense. But the real universe is always one step beyond logic.
Frank Herbert – Dune
Exaptation, a term coined by palaeontologists Stephen Jay Gould and Elisabeth Vrba, refers to repurposing a trait during evolution. Initially serving one specific function, a trait can be co-opted for a different purpose. Charles Darwin was the first to propose that a trait’s function can evolve and change over time. This idea was initially referred to as “preadaptation”. However, because this term seemed to imply a predetermined or planned outcome in evolution, which contradicts the concept of natural selection, Gould and Vrba proposed “exaptation” as a more accurate term.
Misunderstandings about evolution are plentiful enough without experts contributing to the confusion with ambiguous language. “Preadaptation” implies planned intentions for future uses of an adaptation. “Exaptation” denotes a new, unplanned use for an existing adaptation that comes about by evolutionary randomness. Consider our fingers: were they specifically evolved for phone scrolling or nose-picking, or did these uses happen by a fortunate coincidence?
Also, Gould and Vrba theorized that a trait might not be perfectly adapted for this new purpose when it takes on a new role. As a result, secondary adaptations may take place to improve the trait for its new purpose, furthering the cycle of exaptation and adaptation. But this theory has faced scrutiny from some researchers. These critics argue that it can be difficult to distinguish between adaptation and exaptation, given that various influences influence genetic traits.
The evolution of bird feathers illustrates exaptation beautifully. Initially, bird feathers may have evolved for temperature regulation but later were adapted for flight. In their current state, bird feathers are best regarded as adaptations for flight.
The evolution of mammalian inner ear bones shows another exaptation example. In the primitive ancestors of mammals, the small bones currently found in the inner ear (known as the malleus, incus, and stapes) were initially part of the jaw hinge. As evolution progressed, these bones gradually adapted for a different purpose – transmitting sound vibrations to the inner ear, a critical adaptation for significantly improved hearing capabilities.
Exaptation is evolution’s way of doing more with less, and it plays a critical role in the history of life.
Elisabeth Vrba
As we’ve seen these shifts in physical traits, similar transformations have occurred in our cognitive abilities too.
Take, for instance, opposable thumbs and the development of writing. Having opposable thumbs is believed to have initially evolved for better gripping and climbing. However, this trait has been adapted in humans for delicate manipulations, such as using tools or writing.
Then, with further refinements on writing exaptations, as Gould and Vrba theorized (secondary adaptations may occur, furthering the cycle of exaptation and adaptation), we eventually arrived at writing systems. A prevailing theory for the development of writing indicates economic reasons, a way to keep track of commerce and trade. Writing has since been adapted for communicating ideas, ultimately reshaping our understanding of the word.
The structure of our brain has also experienced exaptation, undergoing significant changes that reflect our evolving needs and environments. Emerging cognitive functions like reading or arithmetic, which appeared relatively recently in our history, are believed to tap into the idea of ‘recycling’ existing brain structures.
Reading only developed within the past few thousand years, a considerably shorter timeframe than the emergence of early modern humans hundreds of thousands of years ago. It is highly improbable that our brains could have evolved specifically for the purpose of reading within such a limited span.
Cognitive neuroscientist Stanislas Dehaene proposed the Neuronal Recycling Hypothesis, and it suggests that new cognitive functions, such as reading or arithmetic, which arose too recently to have led the evolution of new brain structures, instead “recycle” or reconfigure existing brain areas for these new uses.
Brain tumours could also lead to a form of neural exaptation (existing neural circuits being used for new cognitive functions). In his memoir When Breath Becomes Air, neurosurgeon Paul Kalanithi describes a medical case of a man with a seemingly inoperable brain tumour.
[Before surgery] I reviewed the patient’s MRI and noted that the tumour completely covered the language areas. That is not a good sign. Reviewing the notes, I saw the hospital’s tumour board – an expert panel of surgeons, oncologists, radiologists, and pathologists – had deemed the case too dangerous for surgery. How could the surgeon have opted to proceed? I became a little indignant: at a certain point, it was our job to say no. The patient was wheeled into the room. He fixed his eyes on me and pointed to his head: “I want this thing out of my fucking brain. Got it?”
The attending strolled in and saw the expression on my face. “I know”, he said. “I tried talking him out of this for about two hours. Don’t bother. Ready to go?”
[…]
I slowly removed the enormous tumour, attentive to the slightest hint of speech difficulty. With the patient’s monologue unceasing, the tumour now sat on a petri dish, his clean brain gleaming.
“Why’d you stop? Are you some kinda asshole? I told you I want the fucking thing gone!”
“It’s done”, I said. “It’s out”.
How was he still talking? Given the size and location of the tumour, it seemed impossible. Profanity supposedly ran on a slightly different circuit from the rest of the language. Perhaps the tumour had caused his brain to rewire somehow …
Paul Kalanithi – When Breath Becomes Air
Beyond the realm of biological evolution, innovations in technology or individual personal growth often bear the signature of exaptation. We regularly repurpose ideas, tools, or skills developed for one context to meet new, unexpected challenges.
The GPS technology, developed initially for military use, is now a cornerstone of civilian applications ranging from navigation systems to smartphone apps. Another military project, ARPANET, started as a communication network that could withstand a nuclear attack. Today, this project is known as the Internet. Touchscreen technology was initially developed for air traffic control to simplify the human-machine interface. It is now ubiquitous in smartphones, tablets, and many public information displays.
A tablet called aspirin was a massive success after its efficacy in reducing pain and fever was proven during the Spanish flu pandemic. But with the introduction of new pain relievers like paracetamol and ibuprofen, aspirin’s popularity started to fade. In the 1970s, clinical trials revealed aspirin as an anticoagulant which led to the current use of aspirin as a preventive measure against heart attacks and strokes. This shift is just one example of exaptation in the pharmaceutical industry.
Pfizer originally developed sildenafil as a treatment for angina and high blood pressure. The drug did not perform very well during clinical trials, but male participants reported an unusual side effect: improved erections. Pfizer repurposed sildenafil for erectile dysfunction, marketing it as Viagra.
Minoxidil was developed as an oral medication for high blood pressure. However, it was noticed that patients taking the medication often grew new hair. It has since been repurposed as a topical treatment for hair loss and is sold under the brand name Rogaine.
This kind of repurposing isn’t confined to biological evolution or industries. Exaptation also has immense value in our personal growth and development, where it might be more aptly called “skill transfer”.
As a personal example, I learned more about conflict resolution skills and effective communication by reading How to Talk So Kids Will Listen & Listen So Kids Will Talk than in any other book. Problem-solving, empathy, adaptability, teamwork, and efficient communication are transferable soft skills that I need, either in a high-demand work setting or negotiating rules with my daughter.
Yet, a psychological tendency can sometimes hinder this kind of skill transfer. The Einstellung Effect is a psychological term that refers to our predisposition to solve problems in a specific way, even though there might be more effective ways to solve them. This cognitive bias limits our ability to find novel solutions because we might overly depend on standard methods.
“Old habits die hard.”
Exaptation can serve as a strategy to counteract the Einstellung effect. By its nature, exaptation encourages the exploration of alternative uses for existing tools, methods, or solutions. It involves repurposing something for a function it was not initially intended to serve and so requires out-of-the-circle thinking.
While it is interesting to consider evolutionary exaptations, determining the original function of a trait or why it may have changed over time can be quite complex and challenging to prove. Still, this theory born from the two scientists’ concern that the limited terminology of evolutionary biology was potentially hampering the science’s precision proves that we need an evolving vocabulary as the words we use can shape our views.
Whether the “exaptation” concept term endures or fades, the ideas it has generated are intriguing. The lesson of exaptation (repurposing and doing more with less) is that what worked for us in the past won’t necessarily serve us in the future. We need to make the most of what we have. Perhaps, the skills we never thought much of can become our greatest strengths.
Further reading: The original paper of Gould and Vrba