It's Impossible To Love The Truth And Deny Evolution: Part VI - The Origin Of Life

Abiogenesis is the process whereby once upon a time life arose from non-life. We are not entirely sure how this process arose (although we are not entirely unsure either), but given that God has created a universe of such ingenious proportions, it's not difficult to accept that bringing life from non-life is well within the scope of His cosmic narrative. What we know this far is that all physical things that exist are made from a finite set of constituents called the elementary particles. The manner in which these elementary particles interact with each other is well known; quarks come together to form nucleons, nucleons come together to form nuclei, nuclei combine with electrons to form atoms, atoms combine with each other to form molecules and materials, and so on.

We know about the compounds that pervaded the early solar system, because we know what comes out of stars and what can be carried in by comets. We know this because we can do astronomical spectroscopy and observe the contents of newly formed solar systems. We even know that amino acids, the constituents of proteins (life’s 'workhorses'), are found in space and can be synthesised in a lab by mimicking lightning striking the earth’s primordial oceans. We also know that ancient clays can catalyse the reaction of some of the early compounds on earth into nucleic acids - which are often touted as the 'building blocks' of life. Not only that, but we also know that nucleic acids can spontaneously form the molecule known as RNA. RNA can not only speed up chemical reactions which could confer a biological advantage, but it can work as a template for itself - perhaps the first mechanism of reproduction. However, not all these environments are conducive to the forming of life - in fact, many are impossible incubators. As none of the elementary particles, nor their simplest combinations, can self-replicate in an evolvable way, life can only spontaneously form in environments that enable life to retain its specific configuration of elementary particles that allow reproduction.

We have a universe that is more than 14 billion years old - most of which cannot produce life. However, the elements of the periodic table still allow a rich range of chemistry to emerge; so rich, in fact, that many complex chemicals do exist and undergo reactions. We know that the vast majority of these compounds cannot reproduce under any known environment, but the underlying engine of our physics and chemistry shows that reproduction (self-replication) can happen - it is just such a rare event that it needed a molecule to form a template of itself, against which the compounds in the environment spontaneously formed a copy of the template. Even though our universe has approximately 100 billion galaxies, each with around 100 billion stars in it, nucleotides bonding to create the first RNAs would still be an amazingly rare event in our universe.

What we can extrapolate about the origin of life question is this. In this world, the common states are liquid, solid and gas. We know such incipient life could not exist in solids, because things in solids cannot diffuse around, and atoms vibrate around an average position with too much restriction for life to flourish. Equally, life isn't likely to exist in the gas phase, because the replication machinery has a necessary complexity and weighs too heavily to thrive in the gas phase. The fact that life exists in liquids is because liquids allow signal transduction by diffusion and can act as a suitable solvent for bio-machinery. Life was unlikely to exist in any other state apart from liquid - hence the ‘primordial soup’ metaphor.

The high surface tension, the low viscosity, the boiling point, the melting point and the fact that water expands upon cooling can all be explained by the way water molecules interact with each other - namely that it is capable of making four hydrogen bonds. Why it does this ultimately lies with the laws of quantum mechanics. The Schrodinger equation, when solved for a given collection of atoms, tells us the properties of that collection of atoms. It tells us how much energy we need to pull it apart, or equivalently, how much energy is released when it forms. The same can be said for collections of water molecules. The solution to the Schrodinger equation is found using the same methods, whether we are dealing with water, or ammonia, or caffeine or any other compound we care to study. The properties of water and all other molecules are the inevitable outcome of the natural dispositions of electrons and nucleons. The properties of water aren't arbitrary; they are emergent phenomena of the properties of the universe - just one of a myriad of consequences of the laws of physics.

That fact that life on earth depends on water is a testament to how life has adapted to the aqueous environment found on the planet on which it arose. It seems true that many of water’s special properties played a significant role in allowing life as it is to exist - however, given that the properties of water are just a consequence of the combination of fundamental particles from which it is made, it is no surprise that we complex beings find ourselves on a planet which has this life-enhancing molecule in abundance, as opposed to anywhere else in the universe.

As I recall, biologist Nick Lane has a theory that proton power is no late innovation, but evolved much earlier in the tree of life than we first thought. The first branch in the tree is between the two great groups of simple cells, bacteria and archaea, and Lane reminds us (rightly) that both of these groups have proton pumps and both generate ATP from proton currents, using a similar protein. It seems very likely indeed that both inherited this machinery from a common ancestor, and that this source was the progenitor of all life on earth, including you, me and the oak tree down the road.

It must be said, though, that although traits found in both the archaea and bacteria are most likely inherited from the common ancestor of all life, a few must have been acquired later by gene exchange, thus giving credence to our belief that ‘distinct’ means, in many cases, ‘evolved independently’. We know that this common ancestor possessed DNA, RNA and proteins, a universal genetic code, ribosomes (which are protein-building mechanisms), ATP and a proton-powered enzyme for making ATP. These intricate mechanisms for reading off DNA and converting genes into proteins are rather like a modern cell. Yet there are nuanced differences as well - in particular, the detailed mechanics of DNA replication would have been quite different. Moreover, it looks as if DNA replication evolved independently in bacteria and archaea; that is, most scientists seem to agree that the defining boundaries of cells evolved independently in bacteria and archaea.

So the question ‘what sort of a cell was this common ancestor?’ is, as Nick Lane concedes, a difficult question. Clearly not a cell with no boundaries, that would defy every known chemical law – but seemingly it was a very simple yet sophisticated entity in terms of its genes and proteins, and was powered by proton currents rather than fermentation, but with membranes that are no longer seen in cells today. To compound the point, back then the oceans were very different to what they are now; the primordial oceans were saturated with carbon dioxide, making them acidic, whereas the seas today have more alkaline. Also there was practically no oxygen, and without oxygen, iron dissolves readily – and we can see from our geological studies that the vast banded-iron formations around the world are a result of iron that once dissolved in oceans. As oxygen levels slowly rose, billions of tonnes of iron precipitated out as rust. This almost certainly means that the interface between the alkaline vents and the primordial seas would have been much more conducive to biochemistry than they are today – in fact scientists have found ancient vents with a similar structure and even reproduced them in the lab.

So the theory that ancient alkaline hydrothermal vents were the incubators for life looks very plausible, particularly if hydrogen and carbon dioxide did in fact react in those vents to form simple organic molecules and also release energy. But we still might be wise to proceed with some caution, because although hydrogen with carbon dioxide may well be central to life, energy is still required in the first place to engender this process, so much so that it is probably nigh-on impossible for bacteria to grow by chemistry alone without the catalysing energy. Let me offer an analogy. Think of the energy stored by ATP as equivalent to £1. If it takes £1 to kick-start a reaction, which then releases £2, in theory a cell has gained £1. However, if the only way a cell has to store energy is to make ATP, it can make only one molecule; to make two new ATPs would cost £2. So one ATP would have been spent to gain one ATP, and the spare change wasted as heat. That's not consistent with being alive. Yet Nick Lane is suggesting that the hydrothermal vents would provide a good explanation to this problem, claiming that::

“The fluid from the vents would have contained reactive molecules such as methyl sulphide, which would generate acetyl phosphate, a molecule that some bacteria today still use interchangeably with ATP. What's more, the natural proton gradient would have supplemented this energy source by spontaneously generating another primitive form of ATP called pyrophosphate. Pyrophosphate also acts in much the same way as ATP and is still used alongside ATP by many bacteria and archaea. These bacteria speed up its production using a simple enzyme called pyrophosphatase”.

So the common ancestor of life could harness the natural proton gradient of ancient vents to produce energy, and by some reversing process store energy too, as this system seems to allow cells to save up small amounts of energy, much the same as we save up our loose change and buy something so it no longer becomes waste. This is equivalent to saying that the proton gradients enable cells to grow and then, by their accumulative energy, leave the vents. This means it may well be true that the last common ancestor of all life was not a frivolously spending cell at all, but a thrifty rock riddled with bubbly iron-sulphur membranes that engendered the energy for primordial biochemical reactions. This natural flow reactor, power-driven by hydrogen and proton gradients, catalysed organic chemicals and brought about proto-life (both bacteria and the archaea) that would become the first living cells – eventually producing you, me and the oak tree.

Given the intractability of this subject and the vast domains of time, it may never be possible to know for sure whether or not life evolved by this mechanism, or whether the initial elemental organism with the properties of self-replication happened just once (maybe only once in the entire history of the universe) or several times. But a good case may have been made that hydrothermal vents had the answer. It's worth adding a point I made in my book The Genius of the Invisible God:

"I won't even bring to bear the complication that the tem 'life' is a human construct, upon which we have created a descriptive term for the purposes of classification. The emergence of life is referred to as abiogenesis - which is the point at which the earth's chemistry evolved into a self-replicating system. But the point at which chemistry becomes biology is not an instantaneous moment (and even if it were, it would be an arbitrarily defined human classification). But let's pretend there is one single point in history when we can say that life began - an A to B event of causation.  The putative conclusion begins with 'Therefore, all life is designed' - and from what I've said it is self-evidentially obvious that there are no philosophical conditions under which one can identify a particular point in history as being the beginning of the design of life. All one is doing is looking for the transition from chemistry to biology, but they overlap, and they give no exhibition to any kind of process of divine choreography, because they can be reduced to particles that simulate mere possibility as fluctuations in a quantum field."

The upshot is, the abiogenesis that brought about early life isn't a direct object of empirical study for us - it is probably a one-off or exceedingly rare event that we may only simulate in the lab, where the exact conditions of the actual event are always likely to elude us. But whichever way we cut the cloth, when describing creation - from abiogenesis all the way through to the rich and diverse complexities of life we see after a few billion years of natural selection - we are describing how God has engineered the laws of physics to behave so that it administers His grand narrative.