“Form Fits Function” in Evolution

There is an example of evolution which happens so fast (unlike most cases) that we can watch it in full detail within a human lifetime. That example is bacteria evolving resistance to antibiotics, so I begin with that.

Typically, it is held that only physical structures can evolve (as in not functions, which are non-physical and according to some accounts are just concepts). However, it is found that there is a problem with that since some prominent theories such as functionalism and superorganisms do depend on things having functions. So it is sometimes added that—abracadabra—the evolved structures are also found to have functions. But what if the functions are present, not just at the end, but all along from the beginning of the evolutionary process?

That possibility is what I investigate in this essay. So let’s see if that happens in our example.

The evolution of bacterial resistance to antibiotics begins with an enzyme in the bacterium which does not (at first) cleave antibiotic molecules. But it does cut apart certain other molecules. And what happens is that it becomes modified to attack the antibiotics.

It starts out like any enzyme by having a hole in it, like a keyhole, and only those molecules that can fit into this hole, or active site, will be operated on by the enzyme. So notice that already the enzyme has a function (to cleave a certain kind of molecule), and that the function depends on its structure (only the molecules that fit into its active site will be cleaved). Then it is a question of if the shape of the active site can become changed so that the antibiotic will fit into it. When it has a different structure, then it will have a different function (antibiotic resistance).

So can the structure (the shape of the active site) be changed?

It turns out that it often requires only one random mutation—maybe two—to make the necessary change. Molecular biologists can tell you exactly what molecules have been switched. (It will be different changes to accommodate different antibiotics).

An enzyme is made out of a long chain of molecules like a string of spaghetti, but it is folded over on itself, so it is more like a wadded-up piece of spaghetti. And the manner of that folding creates the active site. But a single change in the constitution of the chain of molecules (in other words, a single change in the DNA coding for how to make the enzyme) can dramatically alter how the enzyme is wadded-up. Different parts of its spaghetti shape align in new ways during the folding. And that can change the size and shape of the active site and enable the antibiotic molecule to slip into the active site and become cleaved.

The change in the structure of the enzyme (its hole) enables it to have a new function (resistance to the antibiotic).

And by virtue of possessing this enzyme with the new function of resistance, a bacterium which possesses it will live when others without this enzyme will die ((at least in the presence of the antibiotic). In that way, the trait of resistance will come to predominate in future generations of bacteria (which in the lingo of biology means that the population of bacteria will have become adapted to an environment with the antibiotic in it; the population as a whole will have evolved to have this new feature of resistance).

But notice that the new function of the enzyme is what created the better survival. Without that new function there is no evolution or adaptation.

So putting that altogether, the chance change in the structure (of the active site) creates a new function (resistance to the antibiotic), and that new function makes it so that the change in the structure survives natural selection so as to predominate in future generations of bacteria. The structure and function work together to evolve the new feature. It is not just about changes in the structure alone.

And of course it is possible for a random mutation to change the structure but not in a way that enables the antibiotic to slip into the active site. In that case, the structure has indeed changed nut not the function, and there is no improved survival. The new function (destroying the antibiotic molecule) is required for the evolution.

Both the structure and function evolve together as both are presented to natural selection.

Evolution is about form fitting function. And it is about form fits function all through the process of evolution, not just in the final product, because form fitting function is what shapes the new features and enables certain ones to survive.

And that makes sense because, as I argued in my first essay, it is difficult to separate form from function in any case. We cannot have one without also having the other. They go together since they are two properties of the same thing. Any object has how it is put together and also what is can do. But furthermore, what it can do depends on how it is put together, and vice versa.

So then why has it historically been so important to try to deny this role of function in evolution, as if evolution is just about making new structures?

The reason has to do with confusions over teleology, as I will now discuss.


Teleology is the philosophical doctrine which holds that processes in nature work towards a goal (as in embryology working towards the goal of creating a whole organism from a fertilized egg). Often, the goals are said to be there “by design.”

Instead of that, reductionist philosophy wants to say that everything is following laws, and when we think we are seeing functions (such as the function of the heart is to pump the blood), that is not the heart working towards the goal of circulating the blood but rather it is just that functions are inventions of our minds. They are just concepts.

And, accordingly, functions cannot be real, and so they cannot be a part of evolution.

For the reductionists, to be able to say that we live is a meaningless Universe following laws is privileged over recognizing functions in our body organs.

But it need not come to that—that is my point—once we realize that functions are there because things fit together. In the biological world view, everything naturally has form fitting function. Form and function evolve together so as to adapt to the environment. That is what is natural.

What has happened is that the argument has emerged that causation can create things having functions, and specifically it is Darwinism that is the causal process making things that have functions in the end (but not during the process). In other words, for reductionists the alternative to teleology is causality. If it must be acknowledged that some things such as body organs have functions, then it can still be said that they are made by the causal process of Darwinism. The functions are not designed as in teleology if, instead, causality made them by natural forces.

But is Darwinism really causal?

My argument is that evolution is neither causal nor teleological because, instead, it is about how random events fit together to the backdrop of the environment. (But if I am correct, then that, too, is not a result of design. An appeal to causality is not really needed to fend off teleology, and we can, instead, talk openly about how Darwinism works rather than surrender to the mindset of reductionism).

So, again, let’s look at some examples.


Causation is when one event is directly responsible for producing the next event, but that is not the case in Darwinism. In Darwinism, neither its “laws” nor the past events preordain what has to happen in the next event. Sometimes the coyote will catch the rabbit, and other times the rabbit will get away. But countlessly many random encounters between coyotes and rabbits will enable some traits, such as camouflage, to prevail in a population. That is because the creatures which accidentally (by mutation) have the colors that match the environment will survive to have offspring more often than those without. In that manner, the population as a whole evolves to have those traits which best adapt it to survive in that environment.

But to work via a lot of random encounters (with random outcomes) occurring within a specific environment, so as to adapt to that environment, is not the same as one event determining what happens in the next event, and that determining the next and the next, as in causality.

But then how do things having functions get made, if not with causality?


It seems pretty easy to suspect that things having functions get made by the same process as camouflage or antibiotic resistance get made, except to acknowledge that it is not causal (being about random events instead of a succession of one event bringing about the next). We need to look closer at what happens when random events occur over and over in the same environment.

The issue with causality is that it is usually portrayed as being about the interactions of physical events, and that, of course, leaves out functions, which are non-physical. But if we see the world in the first place as about form fits function, then we can acknowledge how functions are a part of evolution at every step of the way.

What I propose is that we expand how we typically see the struggle for survival. What is put to the test of natural selection is not just the structure but the structure and the function together.

It is not just the shape of the wing that survives a competition, but also it is being able to fly. And it is not just the structure of the eye that survives, but it is being able to see. The structure and function are together what are tested. And the reason is because the two (form and function) cannot really be separated (except in the minds of Enlightenment thinking where functions are taboo). Form and function exist in how the other also exists (as explained in my earlier essay).

The form is how an object is put together, and the function is how it fits with the environment in order to do something. It is about variations on a theme of things fitting together.

And then there is no abracadabra. The function has been there all along, evolving.

Indeed, now we can say what evolution entails. Random trials are made until there is achieved a structure that functions well in how it fits with the environment. The other attempts, which do not function well, are eliminated by natural selection.

And we can say what it means to “adapt” to the environment. It means that the structure fits with the environment in a way that is functional. That avoids the supposed tautology of Darwinism. (What does it mean to adapt? It means to have fitness. But what does it mean to have fitness? It means to be able to adapt). Instead of that, it means to be functional in that environment.

It is true that that is not formally a tenet of Darwinism. But perhaps it should be: Structure and function evolve together so as to adapt to the environment.

That is how nature can evolve complexities without it being about design.

At the very least, that is what we see in nature. We see a world with the evolving characteristics of structures having functions.

Functions exist really in nature (not just in our minds) because things fitting together exists really in nature.

Fitting together happens.


This essay its the second in a series of three on the subject of Form Fits Function, starting with Form Fits Function as a General Theory of Knowledge and ending with a comparison to other Theories of Knowledge.

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