Chiara Marletto on Extinction [1]

CHIARA MARLETTO: Thank you. It’s a great pleasure to be here. I’ll try to give a physicist’s perspective on extinction. I’ll start with a thought that evolution is a physical process. What we mean by that is whether or not it can occur, and under what circumstances is set by the laws of physics that are the rules that control and constrain the behavior of every object in our universe. The very fact that extinction can occur tells us a remarkable fact about our universe. That is to say, there are things that are capable of undergoing extinction.

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. 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 erode. This 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—its genome, 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. 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’s called constructor theory, and was proposed by David Deutsch who pioneered the theory of the universe of quantum computer. David and I are working 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 are impossible, and why. In this theory we have an exact physical characterization of an object that has those properties, and we call that knowledge. Note that knowledge here means knowledge without knowing the 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. In fact, 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. With any luck that bit of knowledge can be replaced with a better one.

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 arbitrary high accuracy provided that the requisite knowledge is created. 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. So how does knowledge come about? 

Well, 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. 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.

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 that it happens to be traveling in 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. Criticism is tentatively directed to progress, and it’s a fundamentally nonviolent process, which does involve death if not of obstructions. As Karl Popper put it, we can "let our ideas die in our place."

It seems that with the emergence of thinking abilities—which of course emerged by natural selection—a new kind of extinction has become possible that doesn’t involve death, that is based on criticism and on actually criticizing obstructions. It is this kind of extinction, which is not only crucial for the creation of new knowledge, but with the 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 possibilities.

Thank you for listening.