Wisconsin Public Television University Place  The Origin of Life  Paul Davies  3/20/13 UP850  cc >> Okay, this of course, is another lecture in our John von Neumann lecture series. It's sponsored by C4, the Center for Complexity and Collective Computation. It's very generously supported by the Templeton Foundation, by John Wiley, former chancellor, and by our staff, who always to a great job in bringing you in and making the event possible. In this lecture series we've heard, over the last few months, really about information and energy, the internet, free will, consciousness. The common denominator in these talks has been how bringing together elements that are themselves not particularly interesting, in aggregates, demonstrate what we call emergent phenomena, emergent properties. Today we're going to hear about a very intriguing version of that which is how physical systems yield life. Atoms make cells. Cells make minds. This is something that we barely understand. Paul Davies, who we have with us tonight, is perhaps one of the most famous, I think, living theoretical physicists, astrobiologist, best-selling author. 

He's the director of the Beyond Center for Fundamental Concepts in Science, and the co-director of the Cosmology Initiative at ASU, Arizona State University. His research interests are very modest. They include the origin of the universe, the physics of cancer, the origin of life, the nature of time, and foundational questions in quantum mechanics. The way I like to think about it from Wisconsin, it's the kind of thing that you talk about a supper club. [laughter] For us this is just pedestrian. Paul has lectured on scientific topics to a range of illustrious bodies including the World Economic Forum, the United Nations, the commission of the European Union, Google, at Windsor Castle, the Vatican, and Westminster Abbey. I've been thinking about that when I read that, it must be a little weird because that's where you have Newton's monument. For a physicist to be lecturing-- and Paul, I was looking this up. Do you remember what's written on Newton's monument? [Inaudible] Yes, and so the translation is, it's Latin of course, it says, "Here lies that which was mortal of Isaac Newton." Knowing Isaac Newton, you know he wrote that himself. [laughter] So he's written 28 books. 

They've been translated into 20 languages. They include The Mind of God, About Time, How to Build a Time Machine, The Fifth Miracle, The Goldilocks Enigma, and most recently, The Eery Silence. Why have we not heard from extraterrestrial civilizations if they exist? He's won many, many awards. He's won the 1995 Templeton Prize for his work on the deeper implications of science in society and their relationship to religion. The 2001 Calvin Medal from the UK Institute of Physics. The 2002 Michael Faraday Prize from the Royal Society. And in 1999, perhaps the most impressive, he had an asteroid named after him. Officially named Paul Davies. How does he do this? I'll wrap up in his own words, how does one man accomplish this much in a brief lifetime? Here it is, "Somewhere in the great genetic lottery called Darwinian evolution the sporting gene got dropped from the Davies lineage. At school I blundered through cricket, limped through soccer, and sneaked the odd game of tennis. 

So as a boy I developed interest in knife throwing and bomb making, and ground telescope mirrors on the kitchen table. And failing to impress the opposite sex with my lovable nerd persona." In the end I think that last clause is probably the explanation for why he became a physicist. [laughter] So, Paul, welcome. [applause]  >> Thank you, David, for that fulsome introduction. And ladies and gentleman, thank you for inviting me. It's a pleasure to be here, once I recovered from the 80 degree temperature drop. But it's the first time I've been here to Madison and certainly is a very handsome city. I just wish I could walk around a bit more, but after ten minutes I have to retreat inside. What I've seen so far looks quite delightful. As David was saying, I run this thing called the Beyond Center for Fundamental Concepts in Science, and our motto is, "Confronting the big questions." My research tangles with all those, I like to say, all those things you love to discuss at dinner parties, like how did the universe come to exist? And the origin of life, and time travel and space travel, and the destiny of mankind, and so on. 

Tonight's topic is certainly one of those big questions. Let me just test the technology here. Good. Should we have the lights down a little bit? Is that possible? Or is that going to mess up the videography? [inaudible]  Yes, I'll plough on and hope that they come down a little bit because then we can get the slides. That's excellent. Thank you. A landmark event in the history of science took place in 1859 with the publication by Charles Darwin, of his famous book on the origin of species. In this book Darwin gave a convincing account of how life, over billions of years, had evolved from simple microbes to the richness and complexity of the biosphere that we see today. But Darwin conspicuously left out of account how life got going in the first place. In fact, in a letter to a friend he expressed the opinion, "It is mere rubbish thinking at present of the origin of life; one might as well thing of the origin of matter." It's interesting that we physicists have now explained the origin matter. 

We know how matter has come to exist in the universe. But the origin of life remains deeply mysterious. Now it's really three mysteries wrapped up together. It's the when, the where, and the how of life's origin. I'm going to talk a little bit about the when and the where, but dwell mainly on the how. I think that fits in better with the Von Neumann theme. What do we know about when life began? One thing I should say at the outset is all we can talk about is when life established itself on Earth. Now Earth itself is about a third as old as the universe. In case you don't know, the universe is 13.7 billion years old. The solar system is about four-and-a-half billion years old. 

The oldest evidence we have that life was established on Earth, not necessarily began there but established, comes from these rocks here. They're about three-and-a-half billion years old, and they're located in a region of western Australia near a town called Port Hedland. If you choose to go there, I can recommend that you fly to Port Hedland and then you rent something that the Aussies call a bush basher and you go out into the wilderness, and eventually you get to see these rocks here. It's a type of rock, called chert. They don't look very exciting. I took the trouble to go there. I went on a field trip with some colleagues. The reason that they get excited are thee peculiar features that you see here in the rock. They look a little bit like nested ice cream cones that have been sliced through. It's sectioned through layers. 

These objects are what are known as stromatolites. They are, I should point out right at the outset, that these are fossilized stromatolites, which is to say that these themselves were never living things. And they're certainly not living now. They were structures made by living things. If you want to imagine how that comes about you have to drive from this area of Australian called the Pilbara. You drive for about two days until you get to this place here, Shark Bay. And there, these are the living stromatolites. They're just boring looking microbial mats that deposit minerals in a layered manner. So if you got in a time machine and went back three-and-a-half billion years, that's what life on Earth would look like. See? Not very exciting. 

That's the best you had to offer. That's the sort of thing that stromatolites were. It's those fossilized forms that get the scientists excited. It's not the only evidence for life in the Pilbara three-and-a-half billion years ago, but it was the most direct evidence. It does look like life has existed on Earth for much of its history, at least three-and-a-half out of the four-and-a-half billion years. But let me flip to the fact that the solar system didn't form overnight. Again, you all probably know that our sun, with it retinue of planets, formed from a cloud of gas that contracted slowly, and the blob in the middle became the sun, around it a swirling dish of gas and dust that accumulated to make the planets. This didn't happen overnight. It was an extended process that took about 700 million years to properly complete. During that 700 million years Earth and the other planets were being mercilessly bombarded by huge comets and asteroids. 

This is obviously an artist's impression. It would have been a very unpleasant environment for some hundreds of millions years. These impacts were so huge that, in the case of the largest of them, the energy released would have been enough to strip away the atmosphere and swathe the planet in incandescent rock vapor, and boil the oceans dry. So you had this sort of nightmare scenario of an Earth with a cloak of incandescent rock vapor and super-heated steam which would have thoroughly sterilized the surface. The temperature would probably be about 3,000 degrees. These impacts were occurring relatively often, in astronomical terms. Many, many dozens of these very large impacts would have afflicted Earth. You might ask, how do we know that? The answer is really, look no further than the moon. If you go out tonight, you'll see there's a moon. You look up and, almost with the naked eye, you can see that the surface is pockmarked with huge craters and the so called Lunar Maria. 

These are just areas which have suffered cataclysmic impacts which as melted the surface. Because the moon is so close to Earth, we know that whatever happened to the moon, that treatment would have been meted out to out to Earth, but on a larger scale because it's a bigger surface area. We know from the record of the moon that Earth was being bombarded up until a time-- Well, it didn't just cease overnight. A time about 3.8 billion years ago the bombardment began to abate. It hasn't yet finished, as I'm sure you're aware. You'll know that the dinosaurs, for example, were done in by and asteroid or a comet that slammed into Earth 65 million years ago. There's always a chance we will go the same way. Just last month there was a big incident in Russia. Big in human terms. Tiny in astronomical terms, when an object probably a bit smaller than this building, the size of a large house, slammed into an area of Russia. 

It was equivalent of, I think, a 100 megaton bomb. These things occur all the time. But the really big dinosaur-destroying types are much more rare. There's a good chance that you won't die as a result of that. An interesting statistic, I must avoid too many digressions in this talk, but an interesting statistic that if you pick a random person, you're chances of dying from a cosmic impact are about the same as your chances of dying from an airline disaster. You think, how can that be? The answer is that an airline disaster might kill 1,000 people, but a big cosmic impact might kill a billion people. So there's about a one in a million chance per year that there will be a billion deaths as a result of a big impact. A small probability of a big disaster, but the expectation of death is about 1,000 per year, the same as for airline disasters. Okay, well, enough of that. Let me move on to the where part. 

Where did life begin? The short answer is nobody knows, but there are plenty of scenarios. I said Darwin would not be drawn on how life began, or indeed anything about the origin of life, but he did conjecture in a letter to a friend the idea of what he called a warm little pond in which all sort of chemical goodies might accumulate over a period of time. Then energized by sunlight this chemical soup might become evermore complex, bigger and bigger molecules, until after some suitable period of time, maybe millions of years, something might crawl out of it. That became the basis of the primordial soup theory of life's origin. A watery medium rich in chemicals, and then some sort of self-assembly or self-organization, some magic, out of which life eventually emerged. Well, I think you've realized that this bombardment I've been talking about would mean that warm, little ponds are not a very good place to be. My favorite scenario for life's origin, the setting that I think is most plausible, and it's a very fashionable one now, is shown in this picture here. These are deep ocean volcanic vents. If you go down beneath the surface of the sea there are places where there's tectonic activity, where the plates are moving apart. The lava come up, and the lava hits the water, you get a sort of thermodynamic chemical pandemonium. 

These, what look like smoke, these smoke stacks are in fact percipitates. These are super-heated fluids coming up out of the Earth's crust at about 350 degrees and condensing and making chimneys. There actually called black smokers on account of their mineral content. You might think, well, this is a terrible place for life. But it turns out that clustered around these super-heated vents are all sorts of microorganisms, the primary producers that can sustain an entire ecosystem living in total darkness kilometers below the surface of the sea. So it's an ecosystem which in principle could be independent of the ecosystem on the Earth's surface. That is to say, we can imagine a world in which, like Europa, a moon that has a totally ice- covered surface. It'd be pitch black inside but we could still imagine life being sustained by this chemical and thermal energy coming up out of the surface. Are we allowed to take questions part way through? There's a lady there with her hand up. Probably save it until the end. 

Can you remember it? All right. You'll be first, I promise. This provides the right sort of chemical setting perhaps, if we knew what the process was, for life to begin. My own favorite is actually not around these black smokers, but deep in the rocks associated with them. So this is-- when I was a young lad, a student, we were told life is confined to the surface of the Earth and depends on sunlight for it's existence. We now know that life extends deep into the Earth's crust. There's life inside the Earth as well as on the surface of the Earth. How low can you go? Nobody really knows, but some kilometers anyway. If you drill down under our feet there's life down there. Here this is supposed to be a black smoker, so there's life clustering around these things, but deep in the rocks as well. 

I think that offers a lot of opportunity for the sort of chemical magic to turn non-life into life. Now having said all this, we don't know where life began. We don't even know that it began on Earth. It's entirely possible that life started somewhere else. For example, Mars. Mars has always been a favorite for life beyond Earth. Could it be life started on Mars and then came to Earth subsequently. Well, it turns out that Mars, being a smaller planet, cooled quicker, so it was ready for life sooner than Earth. It suffered less of a bombardment and so offered a more favorable environment for life to get started in the first place. However, if life did start on Mars, how would it get to Earth? The following slide explains it all. 

[laughter] Mars, like Earth, gets hit by comets and asteroids with enough force to spatter rocks all around the solar system. Every million years or so Mars will take a hit and these rocks will be flung into space. Some fraction of them, a few percent, will arrive on Earth. In fact, on average, one Mars rock hits Earth every month. You might say, well, how do we know this? The answer is, we have two Mars rocks at my university. There was a time before people were familiar with the fact that Mars rocks existed on Earth in the form of Mars meteorites. When they were so disbelieving and amazed I used to borrow one of these rocks. I was at the University of Adeliade in those days, in Australia. We had a piece of Mars rock there. They'd only just realized that it came from Mars, this meteorite. 

They lent it to me and I carried it all around the world. It's incredible because they're worth millions of dollars, you see. I'd produce it during a lecture like this. How do we know they are from Mars? Because I hold one here in my hand! It was always very dramatic, but I can't get away with it anymore. There too much risk of being mugged. Anyway, the point is, that cocooned inside the rock life would be sheltered from the harsh conditions of space. That's the cold and the dryness, and in particular, the radiation of outer space. It seems very likely that, in a dormant form, microbial spores could go from Mars to Earth and remain viable on arrival. The same in the other direction. It's pretty clear that if you have life on either Mars or Earth, you'll get it on the other planet in pretty short order. 

It may be life did start on Mars and simply came to Earth in this continual debris blasted off Mars by these impacts. As soon as conditions on Earth stabilized it then took root. We just end there. So much for the when and the where. Now I'd like to come on to the main part of the lecture which is the how part. That's the really tough problem. How did life begin? Now, it's very interesting because when I was a student, so this was a long time ago, a very long time ago. I was a student in London in swinging 60's, if that means anything to anyone here. In those days the feeling about life is that it is/was a bizarre fluke, a freak event that occurred just once in the universe. In fact, it was well summarized by Francis Crick. 

He said, "Life seems almost a miracle so many conditions necessary for it to get going." The feeling was that life isn't something that would just occur more of less inevitably or automatically. In fact, Jacques Monod, who got the Nobel Prize for unraveling the genetic code, said, in some sort of sexist manner, "Man at last knows he is alone in the immensity of the universe out of which he emerged by chance." It's true that he uttered those words at the time of -- nihilism. There was a feeling that the universe is hopeless and pointless, and life is hopeless and pointless. It's all just an accident. That was the feeling in those days. Now, fast forward 30, 40 years and now the sentiment is better summarized by Christian de Duve, another Nobel Prize winning biologist. He said that life is almost bound to arise wherever physical conditions are similar to Earth. He has his ringing phrase, "Life is a cosmic imperative!" Here we have the two contrasting views. One is that life is a bizarre freak. It's unique in the universe. 

It would never happen twice. And the other is, give me an Earth-like planet and I will give you life. The extraordinary thing is, the pendulum has swung from extreme skepticism to extreme credulity. But the facts on the ground actually haven't changed very much. We're just as ignorant today, more of less, of how life began as we were in the 60's. Yet, the sentiment has swung the other way. I want to unpack that a little bit. Why do we care whether life is a bizarre fluke or an inevitability? One reason we care is that if it is an inevitability, than it answers the age-old, very deep question, are we alone in the universe? We'd all like to know that. Are we alone in the universe? Well, the one thing that we can be sure of is that there are plenty of Earth-like planets out there. There's a satellite at the moment called Kepler and it's looking at thousands and thousands of stars for the tell-tale sign that they have planets going around them. 

And here's one. Kepler can tell there's a planet, because when the planet passes the face of the star the luminosity of the star dips a little bit. It's a tried and tested method for finding extra-solar planets. You probably know some thousands of extra-solar planets have now been identified. On the strength of that, the statistics we have so far, a lot of commentators will make statements like this, billions of Earth-like planets in the Milky Way alone. There are a hundred billion galaxies in the observable universe like the Milky Way. That's an awful lot of real estate on which life might exist. You will often find statements, no only by media commentators, but by distinguished scientists who should know better, that if a planet is habitable then it is inhabited. The words sound very similar. Oh, it's a inhabited planet. 

If you say a planet's habitable, of course, it does not imply that it is inhabited. The reason is that for a habitable planet to become inhabited, that is to have life on it, the probability for life from non-life has to be reasonable high, reasonable close to one. If you want to be sure that the universe is teaming with life, as many scientist seem to believe with no evidence whatever, than you naturally assume that in Earth-like conditions life almost inevitably arises. Now, the point I want to make is, how did life begin? People often say to me, what are the chances that we'll find-- Oh, no, not that we will find, but what are the chances that there is life elsewhere in the galaxy? The answer I always give is, I couldn't possibly say. Because you can only give the odds of something if you know what the mechanism is. If we knew the process to turn non-life into life we'd be in with a chance of estimating the odd. We don't know what that process is so we cannot say what those odds are. They could be very good odds or they could be terrible odds. We can easily imagine circumstances that turn non-life into life that are so peculiar, so idiosyncratic, that they would have occurred only once in the universe. We could equally imagine that life emerges naturally, as part of some self-organizing tendency of nature. 

We simply don't know. And if you don't know, you obviously can't put the odds to it. But somehow or other it happened once. Somehow or other some sort of chemical mixture transformed itself into a simple living thing. I want to spend the rest of my time, keeping an eye on the clock, telling you about how that might have happened. There are two ways we can investigate this. One is by experiment, and the other is by theory. If we believe that there is some sort of chemical pathway from just a lot of gunk, maybe in primordial soup, to a living thing, it makes sense to ask a chemist how it happens. So you go to a chemistry lab and say, can you cook up life in the lab, in a test tube. This is what Stanley miller tried to do in 1952. 

In a famous experiment he put water and methane and ammonia and hydrogen in a flask, and sparked electricity through it for a week. He was delighted to find this sort of brown deposit that you see here. When analyzed it turned out to contain amino acids. Amino acids are the molecular building blocks of proteins. They are an important biological molecule. Of course, these are not made from biology, these are made just from chemistry. It seemed to a lot of people at the time that if Miller could make amino acids in a week, what could he make in a million years? You know, maybe if you did more of the same, maybe something would crawl out of the flask. You need a bigger budget than the one he had. You might think since 1952 we would have made a lot of progress down this path of pre-biotic chemical synthesis. But it turns out that you can't get very much further. 

People are still trying this. But you don't get very far. You get one or two of the building blocks of life. But the difference between the building blocks of life and life itself are like the difference between a brick and, say, the Empire State Building. You don't explain how to make the Empire State Building by explaining how to make bricks. The problem is the incredible complexity of life. This is something, well, it doesn't show up very well. It doesn't matter. You wouldn't be able to read it anyway. It's a portion of what is called intermediary metabolism. 

It's a sort of flow chart of what's going on inside cells. It's stupendously complex, just mind-bogglingly complex. And that's the problem. Even the simplest living bacterium is so staggeringly complex that the gulf between the building blocks from a Miller-Urey type experiment and even the simplest living thing is colossal. You simply cannot tell, the fact that you can go the first step along a trillion step road, that the rest of those steps are going to be as easy. We just can't conclude that. There's a fundamental obstacle that I want to tell you about that stands between physics and chemistry, and biology. It's a deep, conceptual problem. When we talk about physics and chemistry we use the language of matter, atoms and molecules, forces, reactions, and energy. These are the sort of terms that physicists and chemists converse with. 

There are some in the audience. You know that. But biologist use a completely different language. They talk about a genetic code. They talk about signals, not just signals in the nervous system but chemical signals between cells. They talk about instructions. What is a gene? A gene is a set of instructions, say for a ribosome to make a protein. They're using the language of information. Biology is all about information and information processing. What we're trying to do in explaining the origin of life is to link the world of particles and energy and forces with the world of information and codes and instructions. 

Because these are conceptually in different universes it's very hard to see how these are going to fit together. No amount of atoms will give you instructions, alone, just on their own. We will never derive a concept like instructions from a concept referring to atoms and interactions. There's clearly something else going on here. The puzzle is captured very well by the current president of the Royal Society, also a Nobel Prize winner, Paul Nurse. He says that we should think of life less in terms of chemistry, but more in terms of logic circuits, a little bit like electronics. He says, "We need to describe the molecular interactions and biochemical transformations that take place in living organisms and then translate these descriptions into the logic circuits that reveal how information is managed. This analysis should not be confined to the flow of information from gene to protein, but should also be applied to all functions operating in cells and organisms." In other words, he sees the distinctive quality of life as being the quality of information management. Not chemistry, but information management. That's the point of view that I'm taking, and that I'm going to continue to tell you about this evening. 

So if we're going to think of life as an exercise in information processing and information management maybe we shouldn't ask a chemist. Maybe we should ask a different form of scientist. Maybe we should ask a computer scientist. This is John von Neumann after whom this lecture series is named. What happens if you ask a computer scientist to tell us how life began? Let me show you a screen shot of my computer taken a couple of days ago. This is windows, so you'll recognize this jumble of things. Here's the talk I'm giving now, here's the abstract which I furnished. This happens to be my wife. And this in the background is the Taj Mahal. We were there over Christmas. 

It was very, very romantic, you see? So we've got all of this on my screen. You'll be very familiar with this. It's want your computer looks like most of the day. Now if somebody says to you, explain Windows, explain what I'm seeing on the screen. What sort of an explanation might you want? One possible explanation is this. Somebody might say, and it might be a chemist. I've got nothing against chemists. Some of my best friends are chemists. But a chemist might say, I can explain Windows. There's some silicone here and some copper here, and some iron here. 

You know, it's all sort of hooked up together. The assemblage of all of these things explains your computer. Well, what it explains is, of course, the computer hardware. That's important. We need hardware. But what we're really interested in, what makes Windows distinctive from just a mess on your screen, is not the hardware but software. When we're talking about the origin of life we really have two things to explain. We need to explain the substrate, the hardware, of life. But we also need to explain the software. How does the software come to exist? More provocatively, seeing as hardware was there since the beginning of the universe, how did hardware produce software? That's the real puzzle. 

Let's see what von Neumann had to say about it. He asks, is it possible to build a machine that could construct any physical system, including itself? It's often called a universal constructor, sometimes a von Neumann machine. This would be a constructor that would make copies of itself. But the key thing that von Neumann saw is that there are trivial constructors and non-trivial constructors. Trivial constructors might be, for example, crystals. Crystals make copies of themselves. Computer viruses make copies of themselves. Some of these other things are more technical. They're here for the scientists. You don't need to worry about them. 

The point is that these things make copies because the replication operation that takes place is inherent in the basic physics and chemistry. A crystal will make a copy of another crystal because the basic laws of physics and chemistry dictate that. Its structure is already laid down in those laws. That's trivial replication. Life is a non-trivial replicator. What von Neumann saw was that life is replication according to programmed instructions, and that any replicator which is life-like has to not only replicate the hardware but the software as well. It has to make a copy of the program that runs the system and insert that program into the copy before it's a true non-trivial von Neumann replicator. This is a complicated diagram. Many of you might not want to bother with the details. But I just want to say very briefly that in life as we know it a lot of the work is done by proteins. 

I've mentioned them already. They're made out of strings of amino acids, polymers. These amino acids are strung together by little machines, or constructors, ribosomes, plus a lot of other ancillary stuff. The famous DNA, or you make an RNA copy, of the coded instructions. It's a bit like a tape going through that machine. The sequence on that tape dictates the sequence of amino acids that get made by the ribosome. You'll be familiar with that if you know basic biology. But if you don't know basic biology it doesn't matter. All you need to know is that you could, if you wanted to, program the DNA or the RNA to make any string of amino acids you wanted, any polymer that you wanted. This is like a universal constructor. 

It's part of the system, the cell as a whole, which can replicate itself. Here we're getting very close to the idea of the logic and the coded instructions. But the point is, the reason it's non-trivial, is because you can program it to make anything at all. It doesn't just make one thing like a salt crystal makes a salt crystal. Within the class of amino acids strung together it can make anything at all. What you get, the product, of this constructor is not implicit in the laws of physics and chemistry. It's in fact, independsnt of those. It depends just on that sequence. It floats free of, harnesses if you like, physics and chemistry, but it's not a slave to them. So what life makes, of course, is consistent with physics and chemistry, but is not dictated by physics and chemistry. 

That's a really important point. What we've got here then is ribosomes can be instructed by DNA to make any sequence of amino acids that you want, and this non-trivial type of replication is programmable, and there's indeed a genetic code that converts the instructions on the DNA into the necessary sequence of amino acids. It's mathematical code. There could be many, many different codes. There's a particular universal code that applies to pretty much all life on Earth. The reason that you need such a code is because the world of DNA, nucleic acids, and the world of proteins and amino acids and chemically are completely disparate. So they deal with each other mathematically through an information channel. The complexity of life and it's ability to replicate, and be like a von Neumann constructor, hinges on the fact that they communicate in mathematical code and not in chemistry. In other words, they communicate with software not with hardware. That's the really important point. 

I've said that, in principle, you can reprogram DNA to do anything you wanted, or to make anything you wanted. How do I know that? This is a guy who did it. This is Craig Venter. He famously reprogrammed something called mycoplasma genitalium to make mycoplasma laboratorium, his own microbe in the sense that the DNA, or the genetic instructions, he created on a computer. In fact, in addition to the genetic instructions, his e-mail address is also in there as well. It's like a trademark. You can reprogram life like that, and that is a good demonstration of the fact that it's flexible. That's what a non-trivial replicator does. It's very, very different from something like a crystal. But that's not all. 

The other point about biological information is that it doesn't sit there. DNA doesn't just-- it's not inert. It does stuff. That is, it implements a program and makes a difference in the world. You only have to look out the window to see that life makes a difference. Life does stuff. Now, when you get down to the level of the genetic sequence, here we have the famous four-letter alphabet, and here you have some others. You can't just look at these, unless you've got a prodigious memory, you can't just look at these and say which is a coding sequence and which is just junk. Or which is Craig Venter's e-mail address. You can't tell be looking. 

At the local level there is nothing life-like about that molecular sequence. It becomes life-like when you take that set of coded instructions and insert it in a cell, a big complex system. Then, in that context, it does stuff. So here we can distinguish between any old bits of information. Such as, if I scatter coffee beans on the floor, there are certainly bits of information encoded there in the sense that you need to specify information to tell me where the coffee beans are. It doesn't mean anything. It's not instructional. Biological information carries instructions. It has a context. There is a molecular milieu that can interpret and act on those instruction. 

The slippery concept of biological information, it's quite different from what's often called Shannon information, which is just a measure of the number of bits. The point is the biological information has a quality over and above how many bits. It's got a quality of being instructional, or if you want to push it, meaningful or semantic. But the other point I'm trying to make is that this information is manifest only in global context. You can't tell at the local level. There's a flow of information from local to global, a bottom-up flow. But that's not all either. In addition to a bottom-up flow we see that there's also a top-down flow. Let me show you the most amazing thing. I could hardly believe this when I first learned about it. 

This is a funny little worm called a planarian. I don't think I've ever seen a live one, but apparently these days high school kids muck around with them. This is an interesting thing to try. This color-coded picture of a planarian's innards shows the electric field. That this end of a planarian, the little worm, is positive, and this end is negative. They come with an electric polarity. It's a few millivolts between the ends. Why am I telling you this? Well, the answer is that using electricity you can change the morphology of the planarian. Now the reason that high school kids like them is that you can cut them up and they grow a whole new worm. You chop them in half and you get two worms. 

They have these regenerative powers. But if you manipulate the electric fields in the right way, you can grow a plantarian, here you see, with two heads. Or if you flip it around the other way, you can grow a planarian with two tails. This is work that is done by Michael Levin at Tufts University. I asked him, are these ones really stupid? You know, compared to these. He said, it doesn't see to make too much difference. [laughter] This is a field which is known as epigenetics. There are people, I know, in this room who work in this field. Epigenetics is all-- we think of genetic as like digital information. I like to think of epigenetics as like analogue information. 

It's all the additional constraints or influences which determine how genes up-regulated or down-regulated, switched on or switched off. Electric fields are part of epigenetics. An electric field will determine which genes are up-regulated or down-regulated. But the genes are down at the microscopic level, so this is an example of what we might call top-down causation. An electric field is a global thing across the whole organism but it will determine what happens down at the molecular level. So we see the thing that characterizes biological information is like a two-way flow. We start at the bottom here with genes and proteins and pathways, and on and on to the organism. We normally think of information as flowing up, but it's a two-way flow. It flows downwards as well. Signals and influences and epigenetic patterning from the broader environment, not just the organism, but the organism's own micro-environment. 

It serves to determine what is going on at the bottom level. It's a up and down flow. Coming back to the original question, how did it all start? Let me take you through these points one by one. Because this is the mystery of life. We want to know, how did software emerge from hardware? That's something I've mentioned. How did non-trivial, that is, programmable information and construction, emerge just from dumb molecules just banging around, and not getting together and doing anything clever? How did digital information storage, in life I've said that DNA is digital information, how did this digital information storage and processing emerge just from analogue information, just some mish-mash of chemicals? Which we can think of as carrying information, but in analog form. How did that come about? And the really thorny point, I think, is how did this instructional or semantic or contextual information emerge just from bits, just Shannon information? Then finally, this top-down information flow. How did that emerge from bottom-up? If we could answer all these questions we'd then be in with a chance, we'd then have a theory of life's origins. Then maybe we could actually compute how likely it is that life would emerge from non-life. Then I could answer the journalists who say, how likely is it that there's life out there in the universe? I could actually give them an answer. 

At the moment I can't say. The arrow bars are infinite. We do not know. I don't know. Nobody knows how likely it is, because we don't know all these things. That's the challenge before us. Can we answer that challenge? Well, I've been talking about experiments, what about theory? Yes, I'm a theoretical physicist, so I've had a go at this. But I have to say that most of the heavy lifting was done by my post-doc, Sarah Walker. There's a paper that just appeared several months ago in Royal Society journal, Interface, on the algorithmic origins of life. It is a sort of manifesto for anyone wanting to work in life's origins. 

All the things that you need to tackle. The conceptual framework that you'll need in order to have a successful theory of life's origin. We don't answer the question of how did life begin. We set out the sort of things that you need to address if you hope to answer that one day. We lay great stress on this transition that I mentioned last, between the flow of information bottom-up and the flow of information top-down. We think, we have mathematical models, that suggest that there's like a phase transition, like going from water to ice, a sudden abrupt jump where that flow, or architecture, of information flips from being just bottom-up to bottom-up plus top-down. We think that that is a well defined step when we talk about life's origin. We think that that is significant, and maybe the step in the origin of life. Meanwhile, and I'd like to wrap this up, supposing we go with the flow and except this wildly optimistic view that so many of my colleagues, that ought to know better, seem to subscribe to, which is that the universe is teaming with life. Yeah, it's got to be out there somewhere. 

It's a great idea. I'd love to believe it's true. I chair something called the SETI Post-Detection Task Group, which means that if E.T. calls on my watch I should be the first to know. So, you know, I have a vested interest in wanting there to be alien beings out there. But I have to tell you that at this time we have no evidence whatever of any life beyond Earth, let alone intelligent life. I'd love it to be out there. How can we test the idea that life does pop up easily in Earth-like conditions? The answer is, we should search for a second genesis of life, search for Life 2, if you like. We're Life 1. Is there Life 2 there somewhere? Where do we find Life 2? Well, if it's true that life emerges readily on Earth-like planets, what is the most Earthlike planet we know? It's Earth. So surely life should have started many times right here on our home planet. 

How do we know it didn't? Has anybody actually looked? Amazingly enough, until a few years ago when I held a workshop at the Beyond Center, the very first one at Arizona State University, nobody had thought to look for an alternative form of life here on Earth. Astrobiologists send a lot of time thinking about, if we go to Mars or if we go to Europa of something, we might find a form of life, but it's life not as we know it. What might it be like? But why don't we look on Earth for life not as we know it? This would literally be aliens under our noses, or perhaps in our noses. [laughter] Aliens not in the sense of, they came from outer space. Though they may have done, as I've explained. They may have come from Mars. But alien in the sense of belonging to a different tree of life. That is, they're so biochemically distinct they're not part of our tree of life. Therefore they'd have an independent origin. They would be two trees, Life 1 and Life 2. 

There may be ten thousand for all I know. Where would we look for such things? Well, I think we would have noticed if it had got beyond the microbial stage. So my feeling is that we look in the microbial realm all around us. 99.9% of microbes, we don't know what they are. This little things, you can't tell by looking what they're made of. You've got to delve into their biochemical innards to see. It could be that when you look under a microscope at the teaming thousands of microbes that one in a thousand might be an alien. It might be something that is life, but not as we know it. It could be that intermingled in the biosphere we know and love is a microbial shadow biosphere of alternative life. People say, give me an example. 

How could it be different? I'll give you a very easy example. It's not necessarily the most likely, but very easy to understand. All life as we know it is based on left-handed amino acids, I mentioned those and right-handed sugar molecules. If you look in a mirror the molecules don't look the same, just like a left hand and a right hand. They don't reflect. So all life as we know it so far, all life so far studied, is left-handed amino acids, right-handed sugars. But the laws of physics don't care left to right when it comes through chemical stuff, electromagnetism. If life were to start all over again maybe next time it would be around the other way. Then you'd have mirror life. If you found a mirror microbe the it would be very unlikely it would have a common origin with life as we know it. 

That's a very simple example. Go look for mirror life. How do you look for it? You get a nutrient medium made of mirror stuff, mirror molecules. You can buy it commercially. See if anything grows in it. NASA did a pilot experiment of that sort and it led to some intriguing results. It's not quite as simple as I'm making out, but I'm trying to give you as clear an example of how you would be sure that this was a completely independent tree of life. There's a whole lot of other ideas as well. I won't go into it because I'm running out of time. You might say, well, how might it have come about? Give me a scenario on the early Earth would have produced many forms of life. 

Here's one. I mentioned the bombardment. This bombardment, of course it wasn't happening every day. There would be periods of maybe a million ten million years would go by before a sterilizing impact. So imagine about four billion years ago Life 1 got going. Then, wham, along came a giant asteroid and sterilized the surface of the Earth. Does that mean that all the life is dead? No, because a lot of matter would be ejected into solar orbit and cocooned inside those huge rocks would be Life 1. It would survive for many millions of years, probably tens of millions of years, going around the sun. Then the Earth would cool down and things would settle down. A million years would pass. 

Then, if it's really as easy as some people think, then Life 2 would get going. Then what happens, some rocks come back-- Oh, I'm sorry. Some rocks come back. Well, what have I don't now? Help. [inaudible]  Go to, like, 50. No? 50 will do. Yup. Right. Some of the-- That's the problem with having the laser pointer on the same device as the-- It advances the same. So some of this material comes back. 

But then we've got Life 2 ensconced on Earth and Life 1 has come back. We now have two forms of life. And then, wham! There's another impact. There may be three and there may be four. This could go on for a long, long time. Of course we don't know that all of these forms of life would survive to the present day. But it seems worth taking a look. My feeling about it is that if there is a shadow biosphere, if it has, or maybe it had in past, but if it's still there now, if there are microorganisms all around us. Or maybe confined to certain peculiar niches which are life not as we know it, then we could be sure. Just one, just one microrobe that is not our life would suffice to show that life is indeed easy to get going. 

Then we would know it would be wide-spread in the universe. Life would in some sense be a fundamental phenomenon, a cosmic phenomenon, and not a bizarre freak. One way of putting that is that we would feel at home in the universe and not like chemical interlopers who are just here by stint of some stupendous accident. For me that would be a very nice thing to believe. But I'm a scientist, so I will go where the evidence takes me. I think we could find that there is a shadow biosphere out there now. We could find it in ten years if we made a concerted effort to look for it. But, of course, most biologists are too busy looking for life as we know it to spot life as we don't know it. If you're looking for A you'll find A, not B. We need to aware of the fact that B might be out there too. 

I want to give the last word to two giants of science. The first of these is Erwin Schrodinger. Schrodinger wrote a famous book that got me interested in this when I was a student, called What Is Life? What I've been trying to do today is to tell you about my take on the nature of life, that it's all about information management. Many other people think it's quite different. They think it's about chemistry, or it's about redox Potential or metabolism and so on. I think the distinctive feature about life is the way it manages information. That the true step in explaining life's origin is not explaining the chemical substrate, although we have to do that as well. I'm not decrying that. But it's explaining the emergence of this instructional information. The point about this is, you can talk glibly about the origin of life. 

People do at dinner parties. How did life begin? But the point is, unless you define life, unless you know what life is, you can't say what it is that began. What I've been trying to do today is to sharpen the conceptual landscape, to try to give you my take on what I think life is. The if I know what it is than I have the chance of explaining how it came to exist. To just use the term life and then try to work out odds, estimate numbers, and answer journalists questions about how likely and so on. Then you're just talking nonsense. That was brilliantly captured in the words that I shall end with by John von Neumann who said, "There's no sense in being precise when you don't even know what you're talking about." [laughter] And at that point, ladies and gentlemen, I will leave it. Thank you. [applause]