Finding its path

It is certainly not my intention to suggest that the origin of life is a scientifically intractable problem, but at this stage of the proceedings simply to register mild surprise at the relative lack of experimental success. There has, of course, been a succession of ingenious experiments that aim to throw light on one or other facet of prebiotic chemistry. The real problem is getting past this first stage, from the early organic 'soup' (however envisaged) to the metabolic and biochemical highway, with a functioning cell as its destination. Self-evidently this end product - the cell - is an immensely complex chemical factory. The path leading to the living cell must have required simpler predecessors, and most probably can be envisaged as analogous to building with something like a modular construction kit. Parts that were formerly independent could then be 'bolted on' at various stages. The difficulty remains: exactly which path, which kit? These questions seem to be virtually intractable, at least at the moment.

Now to me this difficulty appears to be rather strange. Clearly the conditions on the early Earth are difficult to judge with any accuracy. Just how much methane was in the atmosphere? How salty was the ocean? Were there ice caps? And so on. In any of these cases, and many others, the precise values or conditions are elusive. Yet the early Earth must have had some sort of atmosphere, a sea bed with certain clays, volcanic hot springs, and so forth. Strictly speaking the number of variations is very large indeed, but many plausible combinations can be assembled. Perhaps we need to get just the right balance: so much carbon dioxide and no more; a particular mix of clay minerals. ('Steady Trevor with that beaker of kaolinite!'); just a smidgeon of a phosphatic mineral. Maybe, but this is almost getting us into the position of arguing that life was effectively a fluke-like happening, a one-in-a-trillion chance. Perhaps it was. Perhaps the emergence of life was 'almost a miracle' (to anticipate a phrase; see note 89) and given enough time, patience (and money), so too may we stumble on a similar solution. Yet, the general consensus is that far from being a fluke the emergence of life on any Earth-like planet is more or less a foregone conclusion, an inevitability inherent in the self-organizational properties of organic chemistry. So what is the evidence?

Certainly the area dealing with the origin of life has no shortage of enthusiasts: zeal of purpose is combined with an unwavering naturalism. Yet, as Klaus Dose13 reminds us, the research programme, which was initiated by such giants of the field as the Soviet scientist Alexander Oparin, the maverick genius J. B. S. Haldane, and subsequently the chief rejuvenator of this field Stanley Miller, is still fraught with problems. It should all be rather simple. Here are the building blocks, like bricks: today we build something rather simple, say a garden wall, and tomorrow we aim higher, perhaps a cathedral. Despite the many disagreements about the most appropriate experiments and about the environmental milieu, there is a deeply shared belief in the power of the self-organization of prebiotic molecules. In fact this belief in self-organization not only implies a sort of 'biochemical predestination' but, as Dose wryly notes, the research programme has led to an 'era of unconfessed vitalism'. Dose continues with some apt words of warning: '[It has become] abundantly clear that the power of self-organization inherent in macromolecules syn-thesised in cells is based on extremely subtle physical and chemical, and particularly stereochemical, properties [which]', he continues in near-understatement, 'have never been observed in this highly organized form in prebiotic molecules.' He concludes bleakly, 'It appears that the field has now reached a stage of stalemate.'14

Others have reached similarly pessimistic conclusions. John Horgan15 and more notably Robert Shapiro16 have discussed how difficulties crop up at every stage and each step. Not only that but, as Horgan makes clear, the proponents of the various rival schemes of investigation are happy to express scepticism about alternative approaches to the problem, yet for the most part retain quiet optimism that somehow their chosen methodology - with a little bit of luck and another injection of research money - will crack the problem. For many years the cries have been repeatedly 'Breakthrough! Nearly there! A major step! Most significant!!' Let us hope they are right, even if the shouts of acclamation are beginning to sound somewhat hollow. At least Stanley Miller is candid enough to tell Horgan that 'The problem of the origin of life has turned out to be much more difficult than I, and most other people, envisioned.'17

Yet, turning to the mainstream literature we see hardly any inkling of these largely submerged doubts. The practitioners fully realize that the problem cannot be solved by a single masterdemonstration, but will yield only to a patient, chip-by-chip assault on the edifice. The research workers seem always to be frustrated in their quest for what they refer to as the 'one-pot reaction', in which chemicals go in at one end and a replicating system emerges from the other. A survey of this area, which occupies the remainder of this chapter, reveals a picture that can only be described as distinctly discouraging. Indeed, there is a quite general pattern of problems.

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