For ages, we've been trying to trace the origins of life on Earth. How did a barren rock turn into something as flourishing, beautiful, and abundant as we know it? We asked Nick Lane, professor of evolutionary biochemistry at University College London.
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Sophie Shevardnadze: Nick Lane, it's really great to have you with us on our program. As I've said, we have all the big questions, hope you can clarify some things for us. Right, from what I understand energy contained in molecules is pretty much the reason for life on Earth. So energy can't be created or destroyed, it can only be transferred, right? So does this really mean that energy that I consist of, we can trace it back to where life started, maybe even further, Big Bang?
Nick Lane: In principle, I suppose you could, but nobody would have a brain big enough to do that. It's really the flow of energy though, which is the important thing, so the way it's moving from place to place and through us continuously. So we are eating and breathing all the time, and we're changing our molecules all the time. So an easier way to think of it is like there are streams flowing down a hillside and the molecules in the stream in any one moment are not the same molecules, but the stream itself is more or less as we are, a person in that sense, sustained by this continuous flow.
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SS: Okay. So in that sense, what happens to my energy flow and molecules that the energy consists of, once I die? What happens to that energy?
NL: Well, you just break down.
SS: Alright, so it's not transferred anywhere, right? It vanishes, it perishes, or what happens to it?
NL: It’s not transferred into another single being linked with you, it's transferred into the whole fabric of nature, it’s transferred into the worms and the bacteria that eat you up if you're buried. If you're converted into mostly CO2, if you're burned, then then you will be turned into plants.
SS: Alright, so, cinematographically speaking, it will be like spreading ashes on the ocean?
NL: Absolutely.
SS: Right? Okay. Well, you said that life forms can generate energy. And you think that viruses can't do that. But then I look at viruses, and there are new viruses every day, and they mutate. So I wonder, if they're not living, how can they evolve?
NL: Well, I think of them as living. And it's not that we can generate energy, we can convert energy that's in the environment into energy that is useful for us. And that helps us to live, to do everything that we're doing when we're living: to move around, to think, to, you know, build new muscles, whatever it might be. That all costs energy, which we take from the environment by eating food and burning that food in oxygen. The way that viruses get around that is they are parasitic, they simply sabotage our own systems of converting that energy into things and make copies of themselves. So in that sense, we are very similar to viruses, we are parasitic too.
SS: But they're not living organisms, or are they?
NL: If you asked two different biologists that question, you get two different answers. We can't define life, there is no definition of life. And so we can't define if a virus is alive or dead. And the reason is because life is really a continuum from nonliving things to living things. And a virus is in that grey area somewhere in between the two. But it makes copies of itself. It evolves and changes over time. And in that sense, it seems alive.
SS: So if we're okay with a theory that all live organisms generate energy. What would that make sun? I mean, is Sun alive in that sense?
NL: No, we are not generating energy, we are feeding off the energy that's in the environment that's flowing. So the sun is producing a continuous flow of energy –
SS: So it’s a source?
NL: – we’re feeding really on that source of energy.
SS: But how come we can't just feed off the sun's energy and harness it like plants do, for instance?
NL: We can't do that. In fact, it will be virtually impossible for an animal to do that because the amount of energy that plants get by converting sunlight directly into the kind of fuel that we need to live would not be enough to really take a step. Plants are stuck to the spot and there's good reasons for that. They have an enormous surface area, leaves in trees or whatever it may be, which is capturing the sun's light and converting it into organic molecules. But if we were to, you know, – there are actually some animals that have eaten the chloroplasts, which do the photosynthesis in plants, and they get a tiny amount of energy from that because they don't have enough surface area to capture the sun and the process is so slow, that it's not capable of allowing you to run around and chase other things and behave like an animal.
SS: So Charles Darwin and the building we’re having this chat in is named after him –
NL: Yes.
SS: – says that life on Earth appeared in a small pond created from rainfall. You are saying life appeared from a hydrothermal vent on the bottom of an ocean? Is he wrong?
NL: This is a strange thing about Darwin. Darwin was a visionary scientist. And he was right about something very important, which was the theory of natural selection. He was wrong about all kinds of details. He was completely wrong about how genes work, for example. On the origin of life, well, he wrote a short paragraph in a letter to a friend of his that was never published, where he imagined that life might have started in a warm pond on land. And said that it's far too soon for science to be thinking about these questions. So it's very easy. I think a lot of perhaps more religious people like to see Darwin as equivalent to being a prophet. And therefore, if you can show that Darwin was wrong about one thing, then he must be somehow wrong about everything. Darwin was a scientist and scientists are wrong almost by definition about a great deal. But science as a discipline can become more correct over time as we realise, you know, our mistakes, as we begin to correct the mistakes, we begin to approximate on the truth. So no one scientist is ever right about everything.
SS: Okay, so let's assume that you're right about the hydrothermal vents and the beginning of our origins on the bottom of the ocean. You know, there are a number of astrobiologists, and they're saying that similar hydrothermal vents in the frozen seas of the moon of Jupiter and Saturn can be found. What does that tell us? Do you think life could have merged there one day possibly?
NL: It's possible, I'd like to think it's possible, I definitely think it's worth going to these places to find out. It's also, of course, worth going to places where I personally don't think life would have formed because –
SS: Like what?
NL: Well, I personally don't think life would form on Titan, which is another of the moons.
SS: But you think we should go there?
NL: I think we should go there because I might be wrong. And because if life did start there, then it would follow completely different principles to the principles that I talk about. And what any scientist should want to know is the truth in the end. So I personally think that the moon Enceladus is the most plausible place to find life in our own solar system.
SS: What do you make of the theory that life came on Earth from space?
NL: I think it's unlikely. I certainly can't rule it out. It's in a strange way irrelevant because– We'll never know how life started on Earth, we can't know, it’s a historical question. We can't know what the answer actually was because we don't have a time machine, we can't go back 4 billion years. Even if we did have a time machine that allowed us to go back 4 billion years, where should we go? Should we go to the bottom of the ocean? Should we go to a warm pond? And how long should we wait until we see life crawling out of something? So we'll never know how life started. What we can know is how, in principle, kind of sterile planet, just a wet rocky planet with no life on it, what are the driving forces that turned it into a living planet full of life? What are the materials that are needed, what kind of energy flow is needed? We can understand those things. And so we can understand why it is that life started on Earth. I think intellectually, we can understand that. And by that same criteria, we should be able to say, well, life wouldn't have started in these places for those reasons. Now, if life was delivered from space to Earth, we don't know where it came from, when it came from, what the conditions were. It tells us nothing about the principles that govern the origin of life. It only says, well, historically it was like that, which is an accident.
SS: I was speaking recently to this NASA planetary researcher, Jim Bell, and he was actually proving his point that there was life on Mars millions of years ago because there was evidence of liquid water and the climate was warmer. As a biologist, do think it's possible?
NL: Absolutely, it’s possible, it would be, I would say, surprising and disappointing if we never found any trace of life on Mars. I think it would be quite surprising if we found life still on Mars...
SS: Surprising?
NL: Surprising now. It wouldn't astonish me. Plainly, there's nothing on the surface. If we dig down a few meters, it may be that we find things that would almost certainly be virtually dormant. We can tell from the atmosphere of Mars at the moment that there's almost no what’s called disequilibrium. But in the Earth's atmosphere, we have gases like methane mixing with oxygen, which if it was just left alone, if they weren't being continually produced by bacteria, then the methane would react with oxygen, and you wouldn't see these gases as reactive coexisting together in the atmosphere. We see on Mars, there are occasionally tiny little traces of methane, probably produced by geological processes. So if they're still life on Mars, it must be virtually dormant and very little of it. But when there were oceans, and there were oceans 3.5-4 billion years ago, the conditions were really just right, it would be disappointing if life hadn't started there.
SS: Do you think if there ever was life on Mars, or any other planet, for that matter, that we would know of, at this point, life forms would resemble anything like us here on Earth?
NL: Depends on what you mean by ‘resemble’. So I would say –
SS: I mean, humans, probably animals, plants.
NL: If you think about the history of life on Earth, animals appeared quite abruptly about 550 million years ago. And life started 4000 million years ago. So for more than three quarters of the history of the planet, when there was life around, there weren't even any animals. It's very easy to imagine that other planets may just have stayed bacteria forever. In fact, it's much easier to imagine that than it is to imagine that there will be a kind of convergent evolution leading to animals, leading to humans, on other planets as well. And if you just think about animals, you know, an octopus and a human are very different kinds of beings. So the idea that we would get humans, some people think we would, but I personally don't, I think we would see cells. I think we would see life made of carbon. So in that sense, I think it would be similar. But in the structure of animals, I don't think it would be very similar.
SS: Going back to what we're saying right now. It all started from a simple, single-cell organism bacteria here on Earth. How can you explain that at some point bacteria started to develop and then it transformed itself into more complicated forms, and then others just stayed the same bacteria? Like you're saying, here on Earth bacteria developed into animals into humans and probably on other planets, it just stayed bacteria
NL: Well, bacteria stayed bacteria here, too.
SS: I mean, what are the preconditions for some bacterias to become us and others to just stay bacteria?
NL: Most bacteria have stayed bacteria and have stayed bacteria for 4 billion years. They really haven't changed very much. And we can see fossil bacteria in the fossil record from 3.5-4 billion years ago. This is a very strange thing about complex life if we think about plants and animals, but also single-celled things like amoeba, that we all have these big complicated cells that have essentially all same machinery. And then if you look at a plant cell or a mushroom cell down a microscope, and one of our cells, most people couldn't tell the difference. They're really different to a bacterium but very similar to each other. So plant cells have a chloroplast, as well, it does photosynthesis. But apart from that, almost everything else is the same. And so it becomes a very interesting question. Why is it that plants which are rooted to the spot, and photosynthesise to make their own organic matter, and an animal which runs around and eats plants or other animals, and a fungus which dissolves things and absorbs the nutrients, they all have exactly the same structure of cell? Now, this is strange, because you might think that if these are adaptations to a way of life, then they should all look different to each other, but they all look the same as each other. And so there's a kind of an interesting problem at the heart of biology, which is, why is that the case? And given that we're all plainly related, we all share the same structure, then it only arose once. And so you could say, well, maybe it arose on millions of occasions, and we just don't see any evidence for that. But we've looked hard, and we can't find any evidence for multiple origins of complex life. So if you take it at face value, you may say, well, it's really rare, it's very unusual for complex life to evolve. And when it does, you've got all of these curious properties. Now, I think, and not everybody agrees with me, but I think the reason is what's called a symbiosis, but really where one bacterium gets inside another one, and that leads to all kinds of conflicts and resolutions of those conflicts and getting along together, and that changed, really the whole playing field, it changed how selection worked.
SS: Basically, symbiosis of one cell getting into another, if we simplify and break it down, might be a possible reason why things are different, but made of the same cell, right?
NL: For me, that’s the answer, yes.
SS: Is this why, for instance, I don't know, some bacteria are resistant to things and others aren't? Like, for instance, there are bacteria that can survive in acidic pools of Yellowstone. But we all know what happens to humans, God forbid, someone falls inside. Do you know what I mean? Is it the same reason – the cell symbiosis?
NL: No, in part, it is, I mean, effectively, because of this cell symbiosis cells could become enormously larger and effectively more fragile too. I mean, the bigger and more complicated you are, the easier it is to damage you. So if you throw a large cell into Yellowstone –
SS: Is it so?
NL: As a rule, yes. So bacteria are tiny, fairly robust, but simple systems protected by a wall, the cell wall around them. And if you take a bacterium from the floor of the lab and throw it into Yellowstone ponds as well, it would also die. The ones that are living there have adapted to live there over millions of years. But the type of cell being small and robust is much more able to live in that environment than the one of the complicated cells that can give rise to dinosaurs and are also far more likely to fall to pieces and go wrong. And so you throw them into a hot spring and, you know, they'll fall to pieces.
SS: Another thing, I mean, I do understand how, you know, the four basic elements were mixed under certain conditions and they produced a living cell. That I get. Then I don't really understand how that living cell becomes self-governing and conscious? Is it a big question?
NL: It's an impossible question to answer at the moment and one of the most interesting questions probably in all of biology. What is consciousness? And I don't think we have an answer yet, there's two or three possibilities. One of them is that it's really an emergent property from a really complex nervous system. And then if you could make a robot or AI sufficiently complex, then it will become conscious as well simply because all of this processing going on at the same time leads to a kind of an awareness that is unstoppable. That may be the case, a lot of people would think perhaps it's not, and I don't think at the moment we have any way of knowing. Another possibility is that it's a property of matter — all matter. You asked earlier on, is the sun alive? I think the answer is no. But if consciousness is somehow linked to an undiscovered principle of matter or physics, then it would be the case that even the rock would be conscious in some way and then incredibly minuscule way. The question for me is – I think consciousness is linked with life. And I would say lots of lower animals are consciously aware in one way or another. And so I don't link it with a complex central nervous system so much as living cells. And I think it's, again, the process of how energy works, that leads to electromagnetic fields and so on, and that that's where we should be looking for the answer.
SS: Okay. And then there are cells that divide. I mean, you know, it's such a natural thing for us to seek a soulmate to reproduce. So the idea of continuation and survival is really inherent to anything living. But where did that come from first? I mean, was it this first primitive protocell to think, ‘Well, I want to multiply’?
NL: Um, I think the very first cells almost do it inevitably. So if you're in an environment where there's a continuous flow of energy flowing through it, and that is turning gases or rocks in the environment, into organic molecules, and those organic molecules, things, like fats, for example, can form spontaneously under those conditions — the kinds of fats that we find in our cell membranes, or the building blocks of proteins, the amino acids, they can be formed under these conditions. And if you have a continuous flow of energy, and a small proportion of that is reacting and forming these things, then effectively, what you're seeing is growth. And fats will organise themselves spontaneously into cell-like structures. And those will keep growing and as they grow, they become less stable and they divide in two, it's almost a physical property of any system which is growing like that. So to understand why things would divide in two is quite easy. It's just linked to growth. And then, if there is a link with that genetic information, that's a separate question. Where did the genes come from? That's difficult too. But if it's linked, then this cell gets a slightly better set of information genes than this one does, this one might be more likely to survive and divide again, and this one more likely to die. And then we're into standard biology, into natural selection, what Darwin was talking about 150 years ago.
SS: I've heard you say that, at some point, oxygen was a pollutant and then, you know, we've just sort of adapted. And then I see people choking, literally dying and getting really sick in big cities because of carbon dioxide emissions, do you think at some point, the carbon dioxide emission could be like we're breathing fresh air right now when we would actually adapt to it?
NL: There have been some mass extinctions in the history of the Earth where the things that got preferentially wiped out, that were most likely to die were the ones that suffered the most from carbon dioxide, from being poisoned by carbon dioxide. So the one I'm thinking of really is the Permian extinction. This was 250 million years ago. And funnily enough, the animals that could crawl around and dig in the mud, in stagnant mud, and deal with sulfur, so things like hydrogen sulfide and carbon dioxide in large amounts, because they were able to ventilate their respiratory system, they could kind of breathe and get rid of the carbon dioxide, they were more likely to survive than the more simple things that just sat there stuck to the bottom and they had to take whatever was coming at them and so they get, you know, floods of carbon dioxide and they just asphyxiated and died. So we are doing this to ourselves now with global warming. We're gradually asphyxiating the oceans. The oxygen is being driven out of the oceans as they get warmer, their CO2 is increasing and acidifying the oceans slowly. The conditions are a little bit similar to what was happening 250 million years ago, and a lot of scientists are seriously worried that we will recapitulate that. By which time the oceans are dead and there are gases like hydrogen sulfide bubbling out of them killing the life on the shores as well. Now, some life will survive. Maybe not us, maybe not much. But fast forward 5 or 10 million years and the planet will be the same as it is now, absolutely fine, we just won't be on it. We’ll kill ourselves, that’s all.
SS: You know, I've also heard this idea that if you don't use certain parts of your body or organs, like, for instance, astronauts or cosmonauts in space, because they're in weightlessness, their bones get fragile. So, it made me think evolution is not necessarily an improvement. It could also be degradation...
NL: Absolutely it can, yes. A lot of parasites were often seen as being a kind of degraded form of life. Actually, they tend to become simple, because they have to minimise anything that would recognise them as a parasite and kill it, our immune systems, for example. So the simpler they can make themselves, the more likely they are to survive. And so this kind of direction towards losing complexity is quite common with people in space, losing bone mass, that's not necessarily evolutionary in the single lifetime. But if we were to have generation after generation living in space, then it would be selected in the genes, bones will become useless, and so they will be reabsorbed.
SS: You know, we just love to think that we are the pinnacle of evolution.
NL: Yes.
SS: Are we?
NL: No. There is no pinnacle of evolution, everything's flat. A bacterium is the product of 4 billion years of evolution in a specific environment. So are we. So in that sense, we are the lucky survivors at the end of a long process, you throw us into the springs at Yellowstone, and we will not do very well. Bacteria will do much better in that sense. In its own environment, it’s much closer to a pinnacle of evolution. Evolution is going nowhere. It's not interested in us. We are interested in us, and we have a lot to be interested in. But we shouldn't be big-headed about it. I think that there's you know, for more than 100 years, we've known that evolution has no direction.
SS: Nick, thank you very much for this wonderful insight. It's been really a pleasure talking to you.
NL: My pleasure. Thank you very much.
SS: Good luck with everything.