Lee Cronin: 'Aliens could be made from iron'

Lee Cronin explains the potential benefits of evolving inorganic materials
Lee Cronin in his lab
Lee Cronin is attempting to animate inorganic matter through evolution. Photograph: Murdo Macleod

Lee Cronin is the Gardiner professor of chemistry at the University of Glasgow. He also runs the Cronin Group, which is involved in work to "construct complex functional molecular architectures that are not based on biologically derived building blocks". Earlier this year, he gave a talk at TEDGlobal in Edinburgh.

What is inorganic biology?

Inorganic biology is my attempt to try to ask a very basic question about the nature of matter in the universe: can we do biology outside of organic chemistry?

You think biology is defined by evolution?

Yes, evolution occurs in biology but it doesn't occur anywhere else in the natural world. What I mean by evolution is this idea of survival of the fittest and adaptation by replication or birth of offspring. Evolution is a very good way to make complex systems that are robust and function in an environment. Darwin's theory of evolution is in fact a special theory of evolution because it only applies to biology, it only applies to carbon-based life. But four-and-a-half billion years ago there was no life. So I wanted to ask the question: what is the most basic unit of stuff that can independently undergo evolution? You could probably tell me the answer…


Exactly, a biologist might say bacteria are too complex but basically they are single-cell creatures of some description. And so when you set up that you come up with three questions, which are: what is life?; is biology special?; is matter evolvable? If we answer them in reverse order: we know matter is evolvable because biology is made of matter and it needs chemistry material to do its stuff. And if we could make general stuff outside of biology evolve, then we would know how special it is. And then that would lead us to question what is life.

So what would be an example of the general stuff?

All stuff that we have on Earth that isn't replicating.

So you would like to turn the material world into the living world?

We can use the phenomenon of evolution to improve stuff as well as discovering new materials, devices or systems. And that has a profound consequence in itself: not only can we develop a whole new technology, but we might be able to understand how we got here in the first place.

Even a few decades ago, scientists thought that life was incredibly difficult to assemble from nothing and that we were a once-in-a-universe achievement. But actually I think, and I am not alone in this thought, that the emergence of life on Earth is as probable as the emergence of life elsewhere. And so there are many life-forms in the universe but on Earth we are constrained by our bias of carbon and organic chemistry because organic chemistry works brilliantly here. If we were able to prove our assertion that biology is a general phenomenon, not just based on the organic, then we know there is probably other life in the universe.

What I am saying is that all universes can come alive, they just do it in different ways. And in fact in this universe there will be life based on iron or silicon – we just can't conceive of it.

How far have you got in trying to prove biology is a general phenomenon?

We are starting to make inorganic cells in my lab that can start to encapsulate complex chemical reactions. What we are trying to do at the moment is make those cells replicate and basically evolve to establish inorganic biology in the laboratory. So, for example, let's just say we have a material that would normally die or decompose under acidic physical conditions – we keep tinkering with it until it survives, then we move into another environment where we make it really hot and make it survive there. Then we put it into another system where we have a lot of salt where normally it would die, and it survives there. And if we put it in three environments in a row we would get an object that survives under acidic conditions, withstands heat and also high salt concentrations.

We might do this because we want to evolve a sunscreen that is water-resistant for several hours, that gives you factor 30 and when it starts to degrade it starts to change colour so we can see our skin change colour, which tells us we need to reapply it.

How does what you do differ from synthetic biology?

People such as Craig Venter are using existing biological building blocks to make new stuff. They are taking a mysterious machine with mysterious parts they don't fully understand, because evolution has put it there, and they are trying to reprogram the stuff. We don't know what pathways exist in bacterial cells that can be turned on by the deconstruction that synthetic biologists are doing and that worries me a little.

How do you reassure the wider public that this kind of science is not scary?

We're not suggesting that your pen will start to replicate spontaneously. What I would say to the public is we are trying to understand how evolution constructs complex systems so we will be able to predict, say, when the next HN1 virus will emerge.

Evolvable matter will not enslave us because we set the fitness function. We decide what lives and dies, and it won't be set free in the environment. With evolvable matter we have to use extremely sophisticated mechanisms to build our inorganic cell and they simply won't exist in our environment.

To sum up?

I wanted to pare it back to this fundamental question: Darwin observed evolution in biology, but how do we observe evolution outside biology? I am willing to bet that there were some non-biological life-forms present on Earth. They just didn't get very far because biology was so good, it took all the available resources and did its own thing. However, I think that examples of inorganic biology do exist somewhere in our universe. If I am right, then the universe is wired to become alive through evolution and this is a general property of all matter in the universe.