The Origin of Life

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Written by Dr. Nash Popovic

It is estimated that life on Earth appeared as early as 4.28 billion years ago (possibly even earlier). Not surprisingly, this event is still shrouded in mystery, so let’s see how far we have got with unravelling it.

The existing interpretations

Creationism (relatively recently reinvented as ‘intelligent design’) broadly speaking draws upon the Biblical account of the origin of life. It is still seen in some circles as an alternative to the materialist view, so we may as well briefly address this position. Creationists are very good at criticising the opposite standpoint, but less so in providing a coherent support for their own. Genesis is clear that the creation of life is a deliberate act, but the way it is presented raises many issues. Without getting into details, a general problem is the claim that an agency assembled various species as discrete units. This does not seem plausible. The paleontological and micro-biological data indicates that life, in all its diversity, originated from very simple forms and evolved over a long period of time. Contrary to the creationist account, it is evident that more complex organisms have derived from simpler ones, and that there are large time gaps between the appearances of various species (which we will discuss in the part on Evolution). However, this does not necessarily mean that life is a pure accident, as materialists suggest. We will see that their claim is also problematic.

Materialism – from the materialistic perspective, the origin of life is explained as a chance event that occurred through the interplay of physical forces and chemical reactions. The idea that life came about accidentally from inanimate matter cannot be taken for granted, though[1]. Contrary to popular belief, this account is not proven, either empirically or rationally. It has never been demonstrated in a laboratory or anywhere else that a complex structure such as a living cell could arise spontaneously (or through human intervention) from inorganic stuff. Honest scientists are ready to admit this:

We have not yet come up with a convincing mechanism for abiogenesis… And we have come nowhere near creating life in the laboratory. (Silver, 1998, p.339)

In the 1950s, Stanley Miller recreated the conditions believed to exist on prebiotic Earth (a mixture of methane, ammonia, hydrogen and water was exposed to heat and occasional spark-discharges). In a quite short time Miller found some amino-acids in the apparatus (amino-acids are the building blocks of proteins that are in turn the basis of organic life). Recent findings suggest, though, that life arose in an environment far less hospitable than Miller’s glass apparatus. Moreover, many subsequent experiments have not gone much further. Apparently, some researchers managed to create a synthetic organic molecule that could replicate itself, but this should not be confused with procreation. They only replicate in highly artificial, unnatural conditions, and they reproduce only exact replicas. Yet, without mutations, the molecules could not evolve.

Not only has materialism failed to produce a convincing support for its position, but it is also internally inconsistent. Biogenesis is an accepted doctrine in biology, which states that living organisms are produced only by other living organisms, and that the parent organism’s offspring are always of the same kind. Abiogenesis (the notion that life can appear from non-life) is only assumed for the beginning of life, when apparently the first living organism was accidentally generated from inanimate matter. This inconsistency is accepted not because the available data are in its favour, but because it fits current ideology. In his book, The Intelligent Universe, renowned mathematician and astronomer Fred Hoyle asks:

…there is not a shred of objective evidence to support the hypothesis that life began in an organic soup here on the Earth. Indeed, Francis Crick, who shared a Nobel prize for the discovery of the structure of DNA, is one biophysicist who finds this theory unconvincing. So, why do biologists indulge in unsubstantiated fantasies in order to deny what is so patently obvious, that the 200 000 amino acid chains, and hence life, did not appear by chance? (1983, p.21)

In order to survive and reproduce, a single cell organism, however simple, requires at least several components, RNA, (and/or DNA), some proteins and a cell membrane. Furthermore, they all need to function in a synchronous way. Let’s consider in more detail some of these properties to see how implausible random abiogenesis is.

[1] Silver, a biochemist himself, comments: ‘One can believe that a complex system like the living cell is capable of manufacturing large, complex molecules from small, simple precursors, but the original manufacturing mechanism has to come from somewhere’ (1998, p.340).

Necessary conditions for cell formation and its functioning

Molecular properties: a functional cell requires many polymers, large long-chain molecules, built from a number of simple molecules (monomers). These molecules could hardly form spontaneously for several reasons. The formation of polymers requires bifunctional monomers (i.e. those that can combine with two others), and can be stopped/arrested by a small fraction of unifunctional monomers (those that can combine with only one other, thus blocking one end of the growing chain). Prebiotic simulation experiments produce five times more unifunctional molecules than bifunctional ones. Furthermore, many polymers (such as proteins, DNA or RNA) come in two forms, ‘left-handed’ and ‘right-handed’. The building blocks of polymers essential for life need to have the same ‘handedness’ – proteins consist of amino acids that are all ‘left handed’, while DNA and RNA contain sugars that are only ‘right-handed’. Under the right conditions, an undirected environment operating solely on the principles of physical chemistry can produce amino acids (as in aforementioned Miller’s experiment), but they are wrong for life. So created molecules are a blend of left and right hand forms, not the pure ones needed in living things. They could not form the specific shapes required for proteins, and DNA could not be stabilised in a helix and support life if just a small proportion of the wrong-handed kind were present. To produce the correct types of amino acids and sugars, life requires a certain type of proteins called enzymes. However, these complex molecules do not appear spontaneously: they can only be manufactured in a living cell. An equivalent of such a molecular machinery, though, did not exist in the pre-life environment. Silver writes that ‘the probability of a crowd of small molecules forming the needed large molecules to start the long, complex path to a single cell seems to be almost zero’ (1998, p.349).

The cell components: even if all the right ingredients are present, there is still the problem of forming functional cell components by random processes. Proteins and other structures necessary for life consist of many building blocks which must be instantly put together in a certain order. Out of a total number of possible protein structures (within an appropriate size range), only a tiny set have the correct properties from which a simple bacterium can be successfully built. The odds that they will be formed purely by chance are infinitely small. Let us consider the above-mentioned enzymes. Just one is typically comprised of 300 amino acids. Even if it is assumed that a much smaller number of amino acids is needed to form a ‘primitive’ enzyme, the probability of the required order in a single functional protein molecule arising randomly is estimated at 1043 (this is a modest estimate, some go as far as 10195). The simplest living cell must have a minimum of several hundred enzymes and other proteins, which makes a chance arrangement of these molecules vanishingly unlikely.

The cell membrane is another necessary component of a living cell. A universal ingredient of all cell membranes is the phospholipid molecule. This molecule can spontaneously form vesicles in water (‘bubbles’ that resemble in shape the cell membrane), but no one has managed to reproduce this in the experiments that attempt to simulate the conditions on Earth when life began. Moreover, the cell membrane not only maintains the physical unity of the cell, but also performs other vital functions (e.g. allowing energy exchange)[2]. This all requires a relatively complex structure even for the simplest imaginable functional cells.

The above illustrates that the most basic living organisms represent a level of complexity not found anywhere in the inanimate world including that created by humans (viruses, that are, roughly speaking, DNA coated in a protein, do not count, because they need other more complex cells to reproduce, so they could only appear or degenerate to this simplicity later in evolution). It is reasonable to doubt that such a level of complexity could emerge from random chemical reactions. So far though, we discussed only the cell structure. But even if the components of a living cell were somehow formed accidentally, that would be far from enough.

Functioning of a cell: life needs cells that also function and can be sustained long enough to reproduce. To quote Silver again:

The basic problem facing anyone who is looking for the origin of life is to account for the formation of complex, very highly organized, self-sustaining and self-replicating systems out of a mixture of chemicals that, certainly in the early days of the soup, displayed none of these characteristics (1998, p.340).

All the components of a living cell need to be synchronised, to act in a union, in order to maintain a cell. A cell cannot be built piecemeal. Its all major constituents must be created and assembled instantaneously for the cell to function. Without elaborate mechanisms that enable energy intake, chemical distribution, processing of proteins and storing of genetic information to be passed on to the next generation, life could not exist. The components on which these processes depend could not have evolved separately. Proteins cannot form without DNA/RNA, but neither can DNA /RNA form without proteins. And yet, they could not wait for each other. This is because the cell components could not exist independently for very long. As Hazen points out, polymers easily break down:

The large and complex molecules essential to life – proteins with dozens of hundreds of amino acids, RNA and DNA formed with long chains of nucleotides – do not appear spontaneously, even in carefully devised environments with high concentrations of monomers. Indeed, these macromolecules appear to be quite unstable. Even when two monomers link up or polymerise, they often will just as quickly disintegrate or depolymerise under water-rich conditions. (1997, p.165)

The above could be mitigated by water absorbing chemicals or evaporating water by high temperature, but this would require either unrealistic conditions or would lead to the destruction of the polymers necessary to form a cell. Even most nucleotides (monomers that are the building blocks of DNA/RNA) degrade fast at the temperatures that apparently existed on the early Earth. Furthermore, many crucial biochemicals, in fact, destroy each other (i.e. sugars and amino acids mutually react). Living organisms are well-structured to avoid this, but the ‘primordial soup’ was not.

This means that not only did they all need to be produced close to each other, but also within a very short period of time. DNA (and/or RNA), some proteins and cell membrane need to be formed at the right time and place and under the right conditions. However, as Silver point out:

It stretches even the credulity of a materialistic abiogenesis fanatic to believe that proteins and nucleotides persistently emerged simultaneously, and at the same point in space, from the primeval soup. We are in trouble enough without adding events of an astronomical improbability. (1998, p.347)

When all this is put together, it is hard to avoid the conclusion that an accidental beginning of life is highly implausible. Even a hard-line materialist, such as Crick, admits that ‘the origin of life appears to be almost a miracle, so many are the conditions which would have had to be satisfied to get it going’ (Crick, 1981, p.88).

[2] Some of its properties seem to even anticipate complex life forms: ‘…the cell membrane is a unique and ideal fit for its role of bounding the cell’s contents and conferring on the cells of higher organisms the ability to move and adhere selectively to one another. These critical properties are also dependent on the size of the average cell being approximately what it is and on the viscosity of cytoplasm being close to what it is. The membrane must also fit, in that its selective impermeability to charged particles confers additional electrical properties, which form the basis of nerve conduction’ (Denton, 1998, p.209).

Some current hypotheses

The popular argument is that, given a very long period of time, life would occur, even if the chance of its appearance is vanishingly small. It has been calculated though, that accidental abiogenesis is extremely improbable, even if millions of years were available (see, for example, Overman, 1997). Furthermore, the premise on which this claim hinges is shaky: ‘it seems that life appeared almost as soon as the planetary hydrosphere had cooled sufficiently to support it. The time available is certainly short – nothing like the supposed thousands of millions of years that was once assumed to be available’ (Denton, 1998, p.295). According to palaeontologist Roberto Fondi, ‘a spontaneous assemblage of molecules driven by chance cannot account for the emergence of complex organisms — even the oldest algae and bacteria are too complex to have resulted from chance processes in the observed time frames’ (in Laszlo, 1993, p.100).

Not surprisingly, many scientists are at pains to find an explanation which would overcome the problems that the above facts create for the materialistic perspective. Crick, for example, hypothesises that life came from outer space (as the Sumerians and a Greek philosopher Anaxagoras believed long before him). However, this does not solve the problem but only moves it elsewhere. Some speculate that the original cell or cells were much simpler than the simplest existing one-cell organisms. For example, it could be the case that RNA at one point was not only a messenger but also a replicator (assuming the role of DNA too). This possibility faces several difficulties though. RNA is hard to synthesise even under controlled experimental circumstances, let alone in the environment in which biological life was formed. Even when RNA is manufactured, it requires much tinkering to make new copies of itself: ‘…the synthesis of RNA by chance is a highly improbable process, and as yet no one has presented a mechanism by which it might have occurred… even when you do have RNA, the process of self-replication in the laboratory is not at all straightforward, and it requires considerable intervention on the part of the experimenter.’ (Silver, 1998, p.348)

There are a number of other alternatives, but none of them is very credible. It is not possible to examine all of them here, so the final comment is left to a scientist who already did so: ‘although many exotic hypotheses far more speculative than the RNA world have been proposed to close the gap between chemistry and life, none are convincing.’ (Denton 1998, p.294)

That an accidental appearance of life is extremely unlikely seems to be the inevitable inference[3]. Polanyi and Prosch conclude that ‘every living organism is a meaningful organization of meaningless matter and that it is very highly improbable that these meaningful organizations should all have occurred entirely by chance’ (1975, p.172).

We can conclude that both possibilities, that life was assembled/designed and that life is the result of a pure accident, are unsatisfactory. The biblical kind of creation may not have been necessary, but the funnelling of randomness most likely was. So, we suggest the synthesis of what is at the core of these ideas without their ideological baggage. It can be formulated in this way: the cell, as well as the universe, is born out of co-ordinated rather that chaotic complexity. In other words, the intent for life is imbedded in the natural processes. Hard materialists could say that this position concedes too much to the other side, and those who believe in the six days of creation may say the opposite. The middle ground between these opposites may be though more fertile than either of them and worth exploring further. As this will take us beyond the world of matter, material evidence, understandably, will not be always available, but we don’t consider it detrimental. As cosmologist Martin Rees quipped ‘absence of evidence is not evidence of absence’. Still, it is not evidence of presence either, so we will put in place something else instead: the combination of the methods described in in the first part.

[3] It is sometimes claimed (e.g. Dawkins, 2006, p.138) that if the chance is one in a billion (to be generous), and there are a billion Earth-like planets in the universe, life is bound to appear at least on one of them. This is based on either misuse or misunderstanding of statistics: imagine only two planets and the 50% chance of life appearance. Not appearing on one of them doesn’t make the appearance of life certain on the other; the chance is still 50%. By the same token, the chance of life appearing on each of the billion planets remains one in a billion.