The Dirty Secrets of Life by Paul Davies

I think most people here are physicists or have a physics background and to a physicist life seems almost like magic so the two questions that you want to ask when considering the physics of life do we need new physics to explain life and do biological systems hints of what that new physics might be now the founder of this way of thinking was surely Schrodinger who in his famous book what is life dealt with the question of the physics what we might call the physics of living matter and he certainly left open in fact he was inclined to speculate that living matter were not eluding the laws of physics as established up to date is likely to involve other laws of physics hitherto unknown in other words that life does not somehow contradict known laws of physics but our existing laws are inadequate to explain all of the apparently magical properties that life has well this book of course was written a long time ago what is an up-to-date view well if for example we take the opinion of George Whitesides the Harvard chemist highly respected is life just another sort of physical system well he is open to the fact that though there is something special and new going on how remarkable his life he says the answer is very and those of us who deal in networks of chemical reactions know of nothing like it so that's my preamble I'm now going to go through seven or eight dirty secrets depending on when I run out of time so let me just start with dirty secret number one all life on Earth is is not known to be the same life your reading textbooks that all life on Earth is has a common origin and therefore is is fundamentally the same we don't know that the reason we don't know it is because we we have not yet discovered all life on earth most life is microbial and only a tiny fraction of the microbial realm has been characterized let alone cultured and sequenced we don't know what those little critters are under a microscope microbes just look like little blobs you can tell by looking what makes them tick you have to delve into their biochemical innards when you do that for all life so far studied it's the same life but because we've only studied a tiny fraction of what is out there we can't be sure so this opens up the possibility that in the microbial realm there could be forms of life right here on earth which are life but not as we know it we should discover a microbe which was extraordinarily different in its biochemical nature then arguments would rage about whether if you follow the two trees back far enough you would indeed find that there will be a common origin it may not be easy to separate out one from the other for example if we found all known life uses the same genetic code if we found a form of life that had an alternative genetic code then people might argue that there was a simpler precursor code that bifurcated into the two that had been found but I'll give you one example of where it would be very hard to to figure out a common origin and that is nearer life that life as we know it is based on left-handed amino acids and right-handed sugars if we found a form of life with things around the other way it would be very hard to figure out a common origin and so it's worth going to look for such life and indeed there been some limited experiments to try to find mirror life so let me now move on to dirty secret number two and that is that life can't I believe before the understood using ball-and-stick chem Street and in particular I refer to I referred to the dawn of quantum biology they've been a whole slew of publications in recent years books and articles and this if you look at here at the bottom this this talk by Jim al-khalili is a very good and entertaining introduction to quantum biology I probably the expert in the room is Seth Lloyd and you can ask him about this afterwards but there are a number of examples that have been discovered in recent years where it does seem that quantum mechanics is playing a non-trivial role in biology of course I should say at the outset that in in a rather trivial sense all of biology is quantum mechanical because biologies but based on chemistry and we can't understand chemistry without quantum mechanics but I'm when I'm talking about non-trivial effects I'm talking about things I can't angleman superpositions tunneling and so on the example that most people seem to focus on is quantum aspects of photosynthesis this is something that's already in the popular culture Ian McEwan's book solar refers to it I'm not going to go into technical details but this is both experimental and theoretical the other one that is sort of rather charming is avian navigation that some birds particularly the European Robin have are able to navigate using the Earth's magnetic field so there's an avian compass on this compass there is good experimental evidence that this compass depends on quantum mechanical effects radical ion pairs in molecules large protein molecules in the retinas of the birds that are activated and the mixing of the singlet and triplet States gives information about the orientation of the Birdseye relative to the Earth's magnetic field you can read about it for yourself this is not the time to go into details the third one which is being discussed a lot is about flies Drosophila being able to not exactly sniff superpositions but vibrational states and molecules that the lock and key explanation of smell simply is inadequate to explain the high degree of fidelity that in fact all organisms seem to have and the experiments with Drosophila involve due to rating these these molecules and confusing the Flies as to whether the fly left or right so quantum biology is a field that suggests that the traditional ball and stick method of chemistry is going to be an inadequate for explaining life well before I leave that pide what we would like to know of course these are these examples I've given you just the tip of a quantum iceberg or do they suggest as Schrodinger implied that somehow non-trivial quantum effects fundamental to understanding the nature of life is in other words it's the secret of life in quantum mechanics or has even conjectured some sort of post quantum mechanics that's very unclear if quantum mechanics gives some sort of comparative advantage then it's no surprise the natural selection has amplified those capabilities and so that here and there we might expect to see quantum effects but it's it's unclear whether it's going to be more fundamental than that so daddy secret number three there just seems to be a feeling at least in the media that somehow life has been created in the lab or is about to be created in the lab and I just want to note that I do on the head we are very very far indeed from being able to cook up life ab initio in a test tube because there are people out there who've been trying for a long time to do this the experiment everybody usually refers to is the miller-urey experiment in 1952 where the basic building blocks of life amino acids were made rather easily by sparking electricity through a mixture of gases thought to represent the atmosphere of the early Earth oh that's easy enough to do but just because you make the building blocks doesn't mean you're making the whole thing it's a bit like saying comic coming to earth and seeing say New York City and thinking that's amazing how did that appear and then after a lot of work saying we've solved the problem we know how to make a break so making the building blocks is one thing assembling them into the extraordinarily complex and intricate structure that life represents is quite another and yet we see things like this all the time scientist craig Venter creates life for the first time in a laboratory sparking debate about playing God well you know what invented ooh he just re-engineered existing life he took a bacterium a mycoplasma and had the instructions for running the bacteria on the DNA he just replaced it with his own DNA which you can cook up order on the internet gets delivered by FedEx and then you can upload it into the into the microorganism and boot it up and then it and then it runs on on the new software so it's just like taking a computer and just writing some new code and uploading it that's not the same as as making a living thing ab initio so we see lots of lots of this sort of stuff out there so I'm just striving to create life out of nothing well there's a stupendous gulf between making the building blocks and a real genuine living thing and it's not the same as just reprogramming re-engineering existing life data Sookie number four so the textbooks will give you the impression that the nature of life is pretty well understood all the way from DNA right the way up to cells and and organisms and there is a huge huge gap in the middle in the mezzo scopic regime the expert in this is the late John Widom from Northwestern University and my favorite quote of his is that everything you see in between is actually make-believe so this is from a textbook and we we know the structure of DNA very well because you can get at it with electron microscope and we understand the physics of DNA we also understand chromosomes pretty well you can see them under a light microscope and so you've got the bottom and you've got the top but the Me's are scopic region in between is really very murky indeed every cell in your body has about that much of DNA and somehow it's got to be scrunched up and folded into the nucleus and that compactification of the DNA is an immensely complex business and you'll see these diagrams with all of this these windings and loops and so on but the truth is that we we really don't know or understand that so here we have an information-rich highly dynamic highly complex substance this chromatin which is the DNA wrapped around the the proteins and compactified inside the cells but but that substance is largely mysterious and so so that's dirty secret number number 436 number 5 so the dominant principal survival of the fittest there is an impression that that is alone able to account for the richness and diversity of the biosphere but I think it's simply not the case that it doesn't say I'm not saying the Darwinian principle is is wrong but just that it's incomplete it's an incomplete account of the nature of life because in addition so a natural selection can act only upon what is already there and so in addition to determining the survival of the fittest we have to worry about the arrival of the fittest and I can recommend this book by andreas Wagner vogner a cold arrival of the fittest in which he discusses the relationship between genotype and phenotype again that's a simplistic tendency to think that every genotype has an Associated phenotyping changes the insight change the phenotype it's not true there's a very large defeat the genotype space is exponentially large and there's a very large number of genotypes that can map to the same phenotype and so over time the the genomes will explore genotype space and send our tentacles in all these higher dimensions and the neighborhoods of those tentacles can be systems that have very different phenotypes and so there's already a potential in the in the gene pool if you like four very different phenotypes and understanding how those phenotypes spring into existence when conditions change is that is something which is essential to understanding the full picture of of evolution so it's not sufficient to just have selection we need to understand those aspects as well related to this 30 secret number five Lamarckism is not dead reports of its death a premature and that's because of the now clear evidence for epigenetic inheritance so let me just tell you what that is very briefly so every cell in your body has the same genes and yet a liver cell a skin cell a hair cell these are all very different and they're different because different genes get expressed and that's called epigenetics is what determines what gets expressed as opposed to the underlying genes and so we're very clear that during development the gene expression unfolds in the different organs and different cell types and that is well understood and of course when a cell saying the kidney replicates it makes another kidney cell it doesn't make a liver cell or skin cell and so the transmission or propagation of that epigenetic information from what in a self given cell type from one cell to the next is well enough established where it becomes more controversial is whether that epigenetic information can propagate from one generation to the next and there's accumulating evidence that this is indeed the case so what this means is that the experiences of an organism it can affect the germline and pass on epigenetic markers from that organism to the next generation and on to the next generation they've met actually many examples of that this is one particular paper from Nature Genetics to explain that so let me just move on zeta tsuki number six there's little reason to now to think that life may have happened more than once in the observable universe this goes totally against the fashion the I should say that during this F qxi conference I'm also having to skype into the breakthrough listen conference which is taking place in Silicon Valley breakthrough elisany's is the hundred million dollar project that yuri milner is funding to try to detect signals from extraterrestrial intelligence and i'm great supporter of that I think's a wonderful idea but I have to say that the current fashion of supposing that the universe is going to be teeming with life is is based on no evidence whatsoever we don't know how life began in fact Creek many years ago said life on earth seems almost a miracle so many of the conditions through it to get going Jacques Munoz says man someone sexist Lee at last knows he's alone in the unfeeling immensity of the universe out of which he emerged only by chance so the prevailing view then was that life is a stupendously improbable accident it's so complex so specific in its nature that it would never have happened twice in the observable universe and that was certainly the prevailing view in the 60s and 70s so looking for life beyond Earth one might as well have professor interest in looking for fairies it was self evidently the case that life was a bizarre aberration and extraordinary phenomenon restricted to earth but then 20 years later Christian de Duve was almost was able to write that life is almost bound to arise wherever physical conditions are similar to earth and he calls it life is a cosmic imperative that so Darwin it's interesting refused to be drawn on the subject of life's origin it's me rubbish thinking a present of the origin of life one might as well think of the origin of matter is it but the point I want to make is that if you don't know the process that turned non-life into life you can't estimate the odds it could be that there is a mechanism that means that that transition is really rather probable and that the universe is teeming with life but things we don't know what that mechanism is we can't estimate the probabilities so you can't estimate the odds of an unknown process it's the point I want to make many people don't seem to realize this I want to say it again you cannot estimate what unknown presence so so when journalists ask me and say often do how likely is it do you think that you know et is out there or is life out there or something I say it if that question cannot be answered because you can only answer a question how likely is something if you know what is the mechanism that does it they knew at your room with the chance contrast that with the other problem that if life gets going on another planet how likely is that the microbes will evolve to some sort of complex intelligent radio telescope built eeper RT where we know the mechanism that did that it's it's Darwinian evolution and a few other bells and whistles added so although we can't actually do the calculation at least we know how to think about it we don't know how to think about the transition from non-life to life and that's the really big step and that's the really big unknown factor so that just means we can say nothing useful at all about life elsewhere in the universe it could easily be that the the odds against life forming anywhere in our Hubble volume 10 to the 23 potential sites is a trillion trillion trillion to one against they could very easily be the case or it may be that it's quite likely just can't say anything at all and the final dirty secret well actually it's the final one but I'm not going to go into it to too much a lot of people say well the fact that life started on earth so quickly proves he can't be that hard to get going simply not true as Brandon Carter pointed out you

Channel: FQXi

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Keywords: Paul Davies, fqxi, biology, cosmology

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Length: 21min 13sec (1273 seconds)

Published: Tue Nov 15 2016