Chiara Marletto — Extinction: a Constructor-Theoretic View

I’ll try to give a physicist’s perspective on extinction. I’ll start with the thought that evolution is a physical process, and what we mean by that is that whether or not it can occur, and under what circumstances, is set by the laws of physics, the rules that control and constrain the behavior of every object in our universe.

The very fact that extinction can occur tells us a very remarkable fact about our universe. That is to say: that there are things that are capable of undergoing extinction. So, what are those things? Well, they have several distinctive properties, but in the first place, they must display some sort of resiliency, a tendency to remain instantiated in physical systems.

This post is a transcript of a talk presented by Chiara Marletto and available on YouTube. Some paragraphs are prefixed by links into the video at that point in time. The transcript is provided to aid conversations about the tremendously important ideas presented. Some sentences are edited for easier reading from the form in which they were spoken. All copyrights belong to their respective holders.

Now, under our laws of physics, physical systems have a tendency to fade away. So, the only way that resiliency can be achieved is by those things being copied from one physical instantiation to a new one when the former is about to wear out. And that resiliency is the very reason why we talk about their going extinct at all.

To understand what I mean, consider a bacterium, for instance. What can go extinct is not the particular set of atoms that instantiates the bacterium because that changes every moment. What can go extinct is the recipe for the bacterium, is its genum, its DNA sequence, which can last for billions of years.

That is what biologists call a replicator. It has the property of being copied from one generation to another, and in fact, it has the property of striving for being copied. It can cause transformations that are directed to its own replication, and retain the property of doing so again and again.

3:22 What we’ve now come to is that what can undergo extinction can be generally characterized as being a “replicator” that tends to remain instantiated in physical systems, and can cause transformation to occur, retaining the property of causing them again and again.

There is a new fundamental theory of physics that is called Constructor Theory, that was proposed by David Deutsch, who pioneered the theory of the universal quantum computer, and David and I are working on this theory together.

The fundamental idea in this theory is that we formulate all laws of physics in terms of what tasks are possible, what tasks are impossible, and why. In this theory, we have an exact physical characterization of an object that has those properties (ie replicator), and we call that knowledge. And note that knowledge here means knowledge without a knowing subject, as in the theory of knowledge of the philosopher Karl Popper.

We’ve just come to the conclusion that the fact that extinction is possible means that knowledge can be instantiated in our physical world. Extinction is the very process by which that knowledge is disabled in its ability to remain instantiated in physical systems because there are problems that it cannot solve. And with any luck, that bit of knowledge can be replaced with a better one.

5:08 In Constructor Theory, knowledge has a central role because it’s a principle of Constructor Theory that whatever transformation is not forbidden by the laws of physics can be performed to arbitrarily high accuracy provided that the requisite knowledge is created.

And note that there are no intermediate possibilities. Either something is forbidden by the laws of physics, or it can be achieved given enough knowledge. This places knowledge center-stage in our universe and in fundamental physics.

5:48 So, how does knowledge come about? Here we come to extinction again because the laws of physics do not contain knowledge in this sense, neither do the initial conditions of our universe. The idea that they do, which is called Creationism, is anathema to everyone here. So, it’s an interesting insight from Constructor Theory that the only way knowledge can be created under these laws of physics is by a non-directed process of trial and error correction steps.

This is true of both natural selection, and of the knowledge creating process that occurs in people’s minds. But, here we come to a fundamental distinction between the two because in natural selection, the only way a non-adequate theory or idea, a non-adequate recipe for a bacterium can undergo extinction is by actual death of the organism in which it happens to be traveling about.

This is a feature of natural selection, but it need not be so in general for extinction. In fact, in human minds, what happens is that whenever a theory is found to be parochial, that is to say, there are problems it cannot solve, the way it is eliminated, the way it undergoes extinction is by criticism, and criticism is tentatively directed to progress and it’s a fundamentally nonviolent process which doesn’t involve death (if not of abstractions). As Karl Popper put it, we can let our ideas die in our place.

So it seems that with the emergence of thinking abilities, which emerged by natural selection, a new kind of extinction has become possible. One that doesn’t involve death. One that is based on criticism and on actually criticizing abstractions. So, it is this kind of extinction which is not only crucial for the creation of new knowledge, but with a Constructor Theoretic insight, it is part of the very process where our endeavors to perform transformations that are not forbidden by the laws of physics take place.

This is how Constructor Theory lets us see how extinction can be a constructor for future possibilites.