Nick Lane, UCL
This week, weíre looking for life beyond Earth: is there anybody out there? Remarkably, weíre making progress in answering that question. In the last few years, weíve discovered that our galaxy is teeming with alien planets but the big question remains - do any of them harbour life? Coming up, how do we define life and how did it begin; what can we tell about planets thousands of light years away and how many alien civilisations they might be home to? Now to many people, astrobiology means the hunt for alien life, but a big part of this is understanding what life actually is, and whatís needed for it to exist.
Everywhere we look on earth, thereís life in an endless variety of shapes and sizes- from microbes to elephants. But how do we define it? What is life and how is it different from non-life? Nick Lane is a biochemist and he spoke to Chris Smith about the origins of life.
Chris - So, how do we tell whatís alive like a mouse from a brick? Because chemically theyíre both made of very similar things.
Nick - It is notoriously difficult to do and actually, I think itís almost pointless to try to define life. I mean, thereís hundreds of definitions of life out there and theyíre all wrong in one way or another. And the problem is that life is really a continuum from a non-living state to a living state and thereís all kinds of intermediate stages. So, is a virus alive or not is a question which is often discussed. Itís really what life does rather than what it is, and in all these cases, life is making copies of itself and itís using the environment to do so. So, one of the problems with most attempts to define life is that it excludes the environment. All life parasitizes the environment in one way or another. Plants do, they require sunlight, they require carbon dioxide, they require water, and so on, thatís all they require. We parasitize the environment a lot more. We go around eating plants and so on. But essentially, all life is parasitizing an environment which is providing it with its energy needs to make copies of itself, so I think youíd say there are about six different things a cell requires. It requires a carbon source to make more copies of itself, it requires energy to bind things together, to make polymers and to produce more cells, it requires excretion, youíve got to get rid of the waste products and the end products to drive reactions in a forward direction. There has to be some form of compartmentalization, a cell-like structure that makes the insides different from the outside. There have to be catalysts, the beginnings of biochemical reactions, and then, there has to be some form of replication. Now I think those are the six properties of life that we really need to look for.
Chris - You said that there has to be a carbon source. To what extent is the life we see here on Earth so unique to this environment that youíre not going to find it anywhere else or do you think if another planet Earth-like environment exists out there that life would take exactly the same pathway of evolution that it has here and we will be looking at our mirror image out there, somewhere.
Nick - I think thatís actually a good argument to say that life could end up, at least at the bacterial level, remarkably similar. I mean, thereís a strong argument to say that carbon is really better than anything else. Itís much better than silicon, for example, at forming, you know, complex bonds between molecules and itís also available. You know, carbon is far more available in the universe than silicon and also there are gaseous carbon oxides, carbon dioxides, and so on. Itís like a Lego brick, whereas silicon oxides are, you know, sands and so on, you canít really boot-strap yourself up from the ground with sand. You canít build on sand.
Chris - So, youíre sort of saying that because the rules of physics and chemistry are universal throughout the universe, therefore, exactly the same constraints will exist wherever you live Ė Milky way or even the Andromeda galaxy and therefore, youíre gonnaí end up following the same sorts of pathways.
Nick - I think, yes, itís possible. We can conceive that life couldíve operated in different ways but if you think about the probability of finding life, carbon, water, the kind of rocks that are required for hydrothermal systems and so on. They are all very common, so the kind of life that we have here is likely to be the kind of life that we find elsewhere as well.
Chris - The Earthís four and a half billion years old, so how long after the Earth formed, did life first pop up?
Nick - Well, we donít really know. Thereís a lot of arguments about it, a kind of glib answer would be about four billion years ago. There are fractionated isotopes of carbon and so on in ancient rock from about 3.9 billion years ago. Thereís a lot of debate about whether that signifies life or not, but I think most people think on balance, it probably does.
Chris - Where do you think that life came from? What sorts of theories are out there to explain how life arose? Did it arrive de novo, in other words, from scratch here or is it possible that it could have had some kind of injection of some processes from, say, outer space.
Nick - Well, we know for sure that thereíve been plenty of organic molecules delivered from space on meteorites, thereís no question about that. Whether that prompted life on Earth in some way, conceptually what it does really is stock a soup, and so conceptually, itís not really any different to say the Miller-Urey experiment from 50-60 years ago, showing that lightning and UV radiation and so on, can also produce organic molecules, so can hydrothermal vent systems. Itís actually remarkably easy in some ways to produce organic molecules and remarkably difficult to get beyond a soup.
Chris - So, would you be in favor then of the idea that life just spontaneously started, or do think that actually that there is credence to this idea that there could have been life coming from elsewhere, maybe intact life coming from elsewhere in the universe.
Nick - Thereís no evidence to suggest that it did, and actually I think itís a pointless theory in the sense that if it did come from somewhere else, well we still donít know any more about how life started elsewhere. I think weíll never know exactly how life started on Earth but what we can know, what are the principles that lead to the origin of life from a non-living environment, and thatís what weíre looking for in trying to understand the origin of life here. And panspermia, the delivery of life from space, it just moves the problem somewhere else so itís pointless.
The essence of life seems to be a local reversal of mesoscopic entropy.
Alan, I have to respectfully disagree.
Life is a vague term.
OK, if life is not a vague term, please define it! alancalverd, Wed, 1st Oct 2014
Wouldn't life have a special meaning because it can lead to conscious creatures?
This might add some thoughts to the mix.
I detect a genuine brilliance in that statement alan, but if I may, I would like to add one small addition.
How about consciousness. If we would find a crystal able to have a conversation with us, would it be 'alive'? yor_on, Wed, 8th Oct 2014
If I was allowed to make one rule for this and every discussion forum, for all time, it would be to remove any post that uses the word "consciousness" without defining it.
heh, slightly arid (as in dry that is :) response there my dear Alan.
There are very simple machines that are self-aware but far from alive. My present car engine checks its state of health and won't let me drive too fast if it isn't feeling completely happy. I have disconnected the bit that stops me driving into things (reversing sonar that can activate the brake) but the gadget that stops the wheels spinning or locking seems to be quite handy, as are the automatic windscreen wipers. In short, the car knows how to protect itself and its occupants from major trauma, and is aware of its relationship with its rapidly changing environment. Slugs are even more clever, though a bit short of defence mechanisms. alancalverd, Thu, 9th Oct 2014
OK define unconsciousness. jeffreyH, Thu, 9th Oct 2014
That's one interpretations of what self aware could be. Another might be when you're aware about yourself, think I saw some writing that monkeys seems to know that they were looking at themselves, when looking in a mirror. Some other animals just don't make that connection, So let's go get back to that crystal again (ahem, not carbon based though) showing it a mirror :)
And yeah, a Turing machine of sorts. But if it evolved naturally, wouldn't that be intelligence? yor_on, Fri, 10th Oct 2014
As for "Is consciousness a result of the physical processes taking place in the brain? Can consciousness be fully explained by what happens in brain?"
I was thinking of the Turing test there actually. the one where you can't decide if it is a machine or a human you talk too. If we know 'sci fi' :) would get to talk to a 'rock' of some sort, using this test to decide. would that make the rock more 'evolutionary intelligent' than the example in where we would code a computer artificially. It's a side track though. yor_on, Fri, 10th Oct 2014
The point using emergences may be that you're correct in one way, as is Penrose. This consciousness, intelligence, etc is more than the sum of its parts. And it is just that that fascinates me :)
If I understand correctly the emergencies could be understood (at least the weak one). For example we can deterministically explain/trace-back the wet-ability of water from only 2 water molecules. If the emergent property is the result of the collective motion of thousands/millions of molecules, that collective motion can be identified and therefore the emergence understood and no explanatory gap left.
Not really. "In philosophy, systems theory, science, and art, emergence is conceived as a process whereby larger entities, patterns, and regularities arise through interactions among smaller or simpler entities that themselves do not exhibit such properties." Sure, we know the constituents, but what they present us with emerging is new information. yor_on, Fri, 10th Oct 2014
Depending upon the level of intelligence our friendly computer had, that statement could well be argued with. Ethos_, Fri, 10th Oct 2014
Most of the things you feel, touch, smell and taste should be results of emergences. Like sugar being a logical shape of molecules, fitting receptors in your mouth, your brain emerging with a taste of 'sweetness'. Just as you dip your hand in a glass of water, to find a wetness.
You could ask the same from the geometric shape it need to have. Because that is pure geometry as I get it, not chemistry as such. Defining it that way, 'thoughts' definitely belong there too. yor_on, Fri, 10th Oct 2014
What you seem to wonder about is whether you could define some emergence to a specific electrochemical stimulation of the brain though? And that I think should be possible, but I'm not sure? If we use the geometry as a pointer then it is the geometry, shouldn't matter what molecules that geometry consist of, to make the brain emerge with 'sweet!!!'. And it is also so that I think, although not a hundred percent sure, that this 'sweet' experience is more than a cultural, social experience, It's what I think 'hardwired' into the brain. yor_on, Fri, 10th Oct 2014
I have begun to wonder whether the Turing test is just a tautology.
Consciousness and awareness may just be illusions. I recently read an interesting op ed by the author of the book Consciousness and the Social Brain on the New York Times (http://www.nytimes.com/2014/10/12/opinion/sunday/are-we-really-conscious.html?action=click&contentCollection=Opinion®ion=Footer&module=MoreInSection&pgtype=article).
But the 'receiver' of the aware experience is still the same even if the aware experience is perceived as somewhat modified. flr, Tue, 14th Oct 2014
Heard a guy pointing out that we only have a limited amount of different receptors when it comes to drugs. As I gathered it his point was that there are a lot of possible 'drugs' that have no effect at all on us as we lack the equipment to experience them. And what I think it knits to is your argument flr, that there always should be 'something' experiencing it. yor_on, Thu, 16th Oct 2014
I'll make a argument now :)
We have departed from the original question, and settled on a debate about consciousness.
I'd say that anything which can be asleep can also be conscious. PmbPhy, Tue, 21st Oct 2014
I have dormant trees in my garden right now. They are alive, but not growing or doing anything to actively modify their environment or defend themselves (e.g. producing and exuding weedkillers or insecticides). Are they asleep? alancalverd, Tue, 21st Oct 2014
my laptop computer sleeps almost every night chiralSPO, Tue, 21st Oct 2014
Oooh, something measurable, I like it!
I don't know, but I expect at least animals, as dogs, horses, cats etc to be conscious. Although to go from that to define them as intelligent is trickier, but so it is with defining a IQ for a human. If you want, animals have souls :)
Webster's....soul: "an entity without material reality, regarded as the spiritual part of a person."
Has anyone ever read Schrodinger's book What is Life? It's online and can be downloaded at http://bookzz.org/book/651226/daa6c9 PmbPhy, Sun, 2nd Nov 2014