Why is Life so special?
We look around us and see thousands of phenomena – the wind blowing in the trees, a car motoring along a road, a rock tumbling down a stream. We can peer through our telescopes to see further – storms raging on Jupiter, volcanoes erupting on Io, stars forming in the Crab Nebula. But life seems vastly different from each of these. Does it obey the same rules?
A clue to understanding life is the realisation that its dynamics are different than those that rule the non-living. For inanimate objects, the dynamics we see are the product of the disordered motion of billions of particles; they are a kind of average dynamics. At the macroscopic level we see patterns and order, but at the molecular level there is only chaos. But life is different. Inside living cells, there is order right down to the level of that single molecule that governs the form of every creature that lives or has ever lived: DNA. Living dynamics are not a product of chaos but of the highly structured action directed by the molecular ringmaster: DNA.
|Cells capture energy by manipulating electrons and protons within molecular machines called mitochondria|
|The genetic code is held within the DNA or chromosome of the cell. This is transcribed into messenger RNA (mRNA) which takes the genetic message to the protein factories called ribosomes. Here the genetic messages are read and used by the ribosomes to encode the sequence of amino acids strings that make protein chains|
This single particle dynamics brings life under the sway of that most strange of sciences: quantum mechanics. Many people are familiar with the peculiarities of Einstein’s theory of relativity – bending of time and space - but it is less well known that he also helped to found that other triumph of 20th century physics – quantum mechanics. And quantum mechanics is so strange that even he could never accept its implications.
Quantum mechanics is built upon a series of simple observations. One of the strangest is known as the ‘double-slit experiment’.
|Single particles are fired through a pair of slits. The patterns they produce indicate that each particle passed through both slits simultaneously. As well as being in two places at once, individual particles can be shown to inhabit two different energy states, or be travelling in two different directions. Indeed, particles are not limited to being in two states, they can be a billion places at once or in billion states at the same time. However, once the system interacts with the outside world, the ghostly superposition of different states vanishes and the system ‘chooses’ to be in one state, or one place, at one time.|
These simple observations have startling implications but physicists have never been able to agree on how to interpret them. In some interpretations, conscious beings make ‘quantum measurements’ and thereby draw out of the quantum superposition, a particular classical reality. In others, signals travel backward in time to connect every particle in the universe. Today, one of the most popular interpretations, and one that has the backing of Nobel prize-winning physicists , is that there exists a multiverse in which everything that can happen does happen. Although our conscious self inhabits only one branch of the multiverse – our own universe – fundamental particles inhabit the entire multiverse and it is this property that allows them to occupy multiple states simultaneously. Each state is in a parallel universe.
Double-slit experiments were initially performed with just simple particles, electrons, protons, or photons. However as the technology advanced, bigger and more complex systems were shown to enter quantum states.
|Profesor Anton Zeillinger's group in Vienna have recently demonstrated that the fullerene molecule, composed of 60 carbon atoms (the famous ‘buckyball’), can pass through two slits simultaneously. Few physicists doubt that as the technology advances, bigger and more complex systems will be shown to inhabit the quantum world. Fullerene molecules are spheres with a diameter similar to that of the DNA double helix. If fullerene can enter the quantum multiverse then DNA may do the same.|
We have all been brought up on the neodarwinian synthesis of Darwinian natural selection with Mendelian genetics that states that the only significant lifestyle change to befall any microbe – mutations – are entirely random. The dogma states that mutations provide the raw material for evolution but natural selection provides the direction of evolutionary change. This dogma has been the central plank of evolutionary theory for nearly a century. But is it always true?
The proposal that the genetic code may inhabit the quantum multiverse suggests that in some circumstances, it doesn’t hold. Mutations are the driving force of evolution; it is they that provide the variation that is honed by natural selection into evolutionary paths. Mutations have always been assumed to be random. But mutations are caused by the motion of fundamental particles, electrons and protons – particles that can enter the quantum multiverse – within the double helix.
When Watson and Crick unveiled their double helix more than half a century ago they pointed out that mutations may be caused by a phenomenon known as DNA base tautomerisation.
Tautomerisation is essentially a chemist’s way of describing a quantum mechanical property of fundamental particles: that they can be in two or more places at one. Quantum mechanics tells us that the protons in DNA that form the basis of DNA coding are not specifically localised to certain positions but must be smeared out along the double helix. But these different positions for the coding protons correspond to different DNA codes. At the quantum mechanical level, DNA must exist in a superposition of mutational states.
If these particles can enter quantum states then DNA may be able to slip into the quantum multiverse and sample multiple mutations simultaneously. But what makes it drop out of the quantum world? Most physicists agree that systems enter quantum states when they become isolated from their environment and pop out of the multiverse when they exchange significant amounts of energy with their environment, an interaction that is termed ‘quantum measurement’. Cells may enter quantum states when they are unable to divide and replicate – perhaps they can’t utilise a particular substrate in their environment. They may collapse out of those quantum states when their DNA superposition includes a mutation that allows them to grow and replicate once more. In this way the environment interacts with, and performs a quantum measurement on the cell, to precipitate advantageous mutations. From our viewpoint, inhabiting only one universe, the cell appears to ‘choose’ certain mutations.
But is there any evidence for this? When John Cairns of the Harvard School of Public Health in Boston set out to test the dogma that mutations occur at the same rate whether or not they provided an advantage, he found that things were not so simple. Cairns examined bacteria that were deficient in their ability to utilise the milk sugar lactose. When he exposed these bacteria to conditions in which lactose was the only food source, they starved. The cells did not die but instead went into a kind of suspended animation state, called dormancy. Dormancy was a well-known phenomenon so Cairns was not surprised to find that his bacteria managed to survive in this state for many weeks. What did come as a surprise was the discovery that, after a lag period of a day or two, several of his bacterial cells managed to grow and replicate. These replicating cells had acquired a mutation that allowed them to feed on the lactose. What was even more surprising was his observation that the cells only acquired these lactose-eating mutations when lactose was available.
Could bacteria somehow sense that if they modified the DNA of particular genes then they would be able to grow and replicate on lactose and somehow change just the right piece of DNA to achieve that aim? These mutations on demand were termed adaptive mutations, as they suggested that bacterial cells could choose to mutate just those genes they needed to adapt and survive. Cairn’s observations were published in 1988 in the prestigious science journal Nature, and unleashed a storm of controversy. More than a decade later the dust has yet to settle. It is now clear that there were some problems in Cairn’s original experimental design that meant he missed some of the mutations that did indeed occur in other genes. Yet the phenomenon of adaptive mutations persists and has been detected in a wide range of microbes and even in animal cells.
One of the most impressive demonstrations was from Barry Hall of Rochester University who demonstrated that two sites on bacterial chromosome just a few bases apart, were subject to widely different mutation rates, dependent on whether the mutations were adaptive or not. Hall suggested that adaptive mutations are responsible for the rapid rise of drug resistance in bacterial pathogens and even the acquisition of multiple mutations that lead to cancer in animal cells including our own.
Adaptive mutations is still one of the most controversial topics in genetics and provokes the most heated exchanges at conferences. Many scientists simply refuse to believe in their existence. Yet, something new seems to be needed to account for the ease by which some bacteria rapidly acquire multiple mutations. Mutant strains of the TB bacillus have suddenly appeared with resistance to almost every drug available. But how they have so rapidly accumulated so many mutations is a mystery. Unlike many other resistant bacteria that have picked up a package of drug-resistance genes by capturing a new genetic element, the TB bacillus has acquired each resistance by successive mutations – as many as ten independent mutations in a strain recently isolated from Spain. Nobody knows yet whether these mutations are adaptive in the Cairns sense, but it is hard to otherwise account for their sudden emergence. Adaptive mutations take place when cells are not growing and TB is the champion of bacterial dormancy, able to lie low in a host for years or decades. In my laboratory we recently found a high rate of drug-resistance mutations in a close relative of the TB bacillus when it was incubated for many weeks in non-growing conditions. We have not so far managed to repeat these experiments with TB, but they do suggest that this group of bacteria may be capable of adaptive mutations.
The problem with adaptive mutations is that no one can figure a way that information can travel backwards from the environment to DNA, to mutate certain genes. Myself and a physicist colleague, Jim Al-Khalili, recently proposed a novel solution: that DNA may exist in quantum states that are able to sample multiple mutational states simultaneously.
McFadden, JJ and Al-Khalili (1999). A quantum mechanical model of adaptive mutations. Biosystems 50: 203-211.
Quantum superposition is one of the weirdest aspects of a weird science. It is a product of the wave-particle duality that quantum physicists tell us underlies the basic building blocks of matter.
Quantum mechanics is the most thoroughly tested science in human history and no experiment has deviated by one iota from its predictions.
But when will DNA emerge from its quantum state? The borderline between the quantum world and our own is one of the most mysterious aspects of physics but most scientists agree that quantum systems collapse when they become more complex. Our bacterial DNA, existing in a superposition of mutational states will crash out of the quantum world when one of the possible mutations allows it to grow and replicate on lactose, to generate lots of daughter cells. However, when lactose is not available, those same mutations will no longer provide the capacity to grow, so the cell’s DNA will remain in the quantum state indefinitely. Without lactose, the lactose-eating mutation will be no more likely than any other mutation, but with lactose present, that same mutation will constantly pop the cell out of its quantum state to allow it to form the mutant colonies that Cairn’s observed. From our macroscopic viewpoint, the cell will appear to choose its own fate.
Proposing that DNA or cells choose their destiny may appear nonsensical, and it is certainly not intended to imply any kind of conscious choice in simple cells. However, even classical science has a problem with what we call ‘conscious choice’ or free will. According to Newtonian mechanics, future events are entirely determined by what happened before. We may believe we make decisions but classical deterministic science tells us that we are fooling ourselves. Our destiny and every action we make are determined by a series of previous events whose ultimate source is the Big Bang. Quantum mechanics allows an escape from this gloomy outlook because quantum systems are not entirely deterministic. Although bacteria are certainly not conscious and do not know that they are making a decision, I believe those same quantum dynamics – though involving electromagnetic fields rather than DNA – are responsible for what we call our ‘free will’.
Click here for a more detailed argument with equations.
The origin of life
How did it get here? That is the biggest question in biology. A group of bacteria called mycoplasmas are, as far as we know, the simplest self-replicating organisms. Yet they are extraordinarily complex. One of them has recently had its entire genome sequenced: four hundred and seventy genes strung out along 580,070 DNA bases. Surely such a structure could not have arisen by the chance coming together of chemicals sloshing through the primordial soup? The astronomer Fred Hoyle has described the likelihood of random forces generating life as equivalent to the chances that a tornado sweeping through a junkyard might assemble a Boeing 747. The world is just not big enough to evolve life if it relied entirely on chance. Finding plausible conditions that generate the biochemicals necessary for life is hard enough. Stringing those biochemicals together to make life is vastly more difficult. Yet nature seems to have accomplished this feat very early in our planet’s history.
Four billion years ago the Earth was an inhospitable place: hot lava and sulphurous gasses bubbling through its thin crust, comets and meteorites bombarding its surface. By 3.8 billion years, conditions had settled down sufficiently to allow an ocean to form and life was at least possible. But rocks 3.8 billion years old show isotopic signatures of photosynthesis. Microbial fossils are visible in the earliest non-metamorphosed rocks (those that haven’t been melted) that are about 3.5 billion years old. These fossil microbes look like organisms alive today and are likely to have been just as complex. Life may be improbable, but it was quick.
Only the creationists persist with the belief that complex organisms can just pop into existence. For the rest of us, complex creatures must have evolved from simpler ones. We have evolved from primates, primates from shrew-like mammals, mammals from fish, fish from worms, worms from microbes. What makes this scenario so plausible is that each of the stepping-stones is itself a viable creature. Most are still alive today, surviving for the same reasons they evolved millions of years ago – because they work. But where are the simpler microbes? If self-replication can be achieved with fewer that four hundred and seventy genes, why doesn’t any microbe today manage that trick? In fact mycoplasmas don’t manage it very well, they are degenerate organisms, evolved from more complex bacteria called clostridia, by losing genes. They have lost so many genes that they only survive by adopting a parasitic lifestyle, relying on animal cells to make many of their biochemicals. They are unlikely denizens of the primordial mud.
There have been many attempts to answer the origin of life question, from life arriving from space, to life originating as clay minerals. None is very convincing. A relative newcomer to the field is complexity theory. This sister science of chaos theory, examines how complex interconnected systems generate relatively simple patterns of behaviour. The complexity guru, Stuart Kauffman, has proposed that life arose by ‘order from chaos’. But there is a fundamental difference between chaotic dynamics and life. The order we see in phenomena like anticyclones or the red spot of Jupiter is a kind of average order, only visible at the macroscopic level. At the microscopic level of individual particles, there is only chaotic motion. But life is different. A living cell is ordered right down to the level of that single molecule of DNA that orchestrates its every action. Life is not a product of chaos.
Living organisms are the only observable natural phenomena controlled by single particles dynamics. Your eye colour, shape of your nose, even perhaps aspects of your personality, has been determined by the motion of fundamental particles within the double helix that you inherited from your parents. This dependence on the dynamics of single particles brings life firmly under the sway of quantum mechanics.
Physicists who have struggled to come to terms with quantum mechanics have proposed a number of interpretations of quantum mechanics. In one, the world is not real until people look at it. In another, signals travel backwards in time to connect every particle in the universe. Hugh Everett III came up with one of the most remarkable theories. He claimed that we should take the equations of quantum mechanics at their face value. If the equations state that particles can be in two places at once, then we must accept that they can. To make the sums add up to our version of reality, Everett proposed that the two places were in parallel universes.
Revolutionary though this interpretation is, it has the support of many of today’s leading physicists. It claims is that everything that can happen does happen, in the ‘multiverse’. For reasons that are unclear, the large objects we see occupy only one slender branch, our universe, but the fundamental constituents of matter inhabit the entire multiverse.
Consider those chemicals sloshing through the primordial sea: billions of molecules colliding, combining, breaking and reforming to make trillions of new molecules. The likelihood of their random collisions generating a molecule, or even a microbe, complex enough to replicate itself is minute, far too low to have occurred on this planet or even a billion planets. But … and this is a crucial but, that probability is not zero. So long as the events took place in the quantum multiverse then everything that could happen would happen. If there is some non-zero probability that a fantastically improbable combination of molecular collisions could lead to life, then it WILL lead to life, in the multiverse. Life will emerge. And life, by replicating itself to generate larger more complex structures will crash out of the multiverse to yield the world we know. Any small pond could generate life, if it had access to the quantum multiverse.
Once you accept the reality of the multiverse then life becomes inevitable: it had to happen and it had to happen quickly. If you find the multiverse hard to swallow, then you can opt for another interpretation of quantum mechanics. But beware; you still have to account for that experiment with two holes. No one, not even Einstein, could come up with a version of reality less strange than quantum mechanics, yet one that still explained all the existing data. And although the interpretations of quantum mechanics differ in their view of the world, they all make precisely the same predictions as to how the world behaves. The scenario I have presented relates the origin of life within the multiverse, but backward in time signals or consciousness-dependent reality, will generate the same dynamics. In each, life is inevitable.
If you don’t like the multiverse interpretation of quantum mechanics then you can frame this scenario in any interpretation of your choosing. All of the interpretations of quantum mechanics are functionally equivalent and they all make the same predictions. The Copenhagen interpretation would have the earliest events in the origin of life taking place as a probability matrix that becomes increasingly complex with time until it contains within it a measuring device capable of collapsing the wave function. That measuring device is the first living organism.
So life is indeed an extraordinary phenomenon. It inhabits two worlds: the world we know and the strangely structured multiverse. This is what endows life with its powerful dynamics and has promoted the evolution of living creatures to occupy every habitable niche on Earth. I believe those same dynamics, but involving different substrates, are responsible for our own ability to make choices: our free will.
National Institute of Standards and Technology/ Time and Frequency Division – some of the most awe-inspiring experimental work on decoherence, the quantum Zeno effect, etc. is from David Wineland’s group.
Foundations of Physics and Quantum Optics Group, Institut für Experimentalphysik, Universität Innsbruck.– Anton Zeilinger’s group in Vienna, home of the two-slit fullerene experiment.
Quantum Information at Los Alamos National Laboratory – quantum information, quantum cryptography and quantum computing.
Center for Molecular Modeling, National Institutes of Health – an excellent but rather technical guide to quantum chemistry.
H is for h-bar – an excellent outline of quantum mechanics written by Rhett Savage of Reed College, Portland.
Usenet Physics FAQ – answers all your questions.
The Bose-Einstein Condensation (BEC) Homepage at Georgia Southern University (GSU) – see the state of matter predicted by Bose and Einstein.
Decoherence, einselection, and the existential interpretation, Wojciech H. Zurek - The ‘Rough Guide’ to decoherence and the nature of existence.
John Gribbin's Homepage, authors of 'Schroedinger's Cat' and other great book on Physics.
David Deutsch's homepage, author of 'The Fabric of Reality', doyen of quantum computing and the multiverse theory.
David Bacon's homepage at the University of California, Berkeley, with information about quantum computing and lots of links.
Stuart Hameroff’s Homepage – learn all about those busy microtubules and their proposed role in quantum consciousness.
Quantum-Mind email discussion list
Journal of Consciousness Studies
How Thoughts Shape Matter - a commentary by Jack Sarfatti
Patricia L. Foster’s Homepage
Susan Rosenberg’s Homepage
Mutation and quantum mechanics
Per-Olov Löwdin Homepage
Quantum and DNA Computing – can molecules think?
Introduction to DNA Structure – general introduction to DNA with nice pictures
Cell Biology from Gwen V. Childs of the University of Texas
Darwin's 'The Origin of Species' – complete text of the first edition from The National Center for Science Education
EVOLUTION: Theory and History – from UC, Berkeley
The World of Zoologist Richard Dawkins – unofficial Richard Dawkins page
Stephen Jay Gould – Stanford presidential Lecture Series profile
Evolution - selected papers and commentary from Queen’s University, Ontario
Origin of Life
New York Center for Studies on the Origin of Life
Exobiology and the origin of life – National Space Society Website
Origins of Life in the Universe – NASA site
Johnjoe McFadden – Quantum Evolution
Paperback is now available:
Quantum Evolution: Life in the multiverse
some excerpts from 'Quantum Evolution'
John Gribbin - In Search of Schrödinger's cat
John Gribbin - Schrödinger's Kittens and the Search for Reality
Paul Davies - The Fifth Miracle
Paul Davies and Julian Brown - The Ghost in the Atom
Roger Penrose - The Emperor's New Mind
Roger Penrose - Shadow's of the Mind
Richard Feymnan - Lectures on Physics
Quantum Theory and Measurement - J.A. Wheeler and W.H. Zurek
Charles Darwin – The Origin of Species
Richard Dawkins – The Selfish Gene
Richard Dawkins – The Blind Watchmaker
Steve Jones – Darwin’s Ghost (Like a Whale in UK)
Steve Jones – The Language of Genes
Mark Ridley - Evolution
Stephen Jay Gould – Bully for Brontosaurus
Stephen Jay Gould – Eight Little Piggies
Stephen Jay Gould – Wonderful Life
Alexander Graham Cairns-Smith – Seven Clues to the Origin of Life
Return to Quantum Evolution Homepage