One of creationism’s favourite arguments depends on treating chemistry as a lottery in which every conceivable molecular arrangement is equally likely, and the winning combination must appear in a single lucky throw. Count enough possible combinations, announce an astronomical improbability, and declare that a supernatural designer must have intervened. Apart from the obvious false dichotomy fallacy, What this argument ignores is precisely what matters: molecules have physical and chemical properties that make some interactions more likely than others, and complex structures can assemble through successive intermediate stages, in a process that parallels the trial and error of evolution.
Research by scientists at the University of Oxford provides a striking illustration. In a study published open access in Nature, the team followed the assembly of an engineered virus-like particle containing 60 protein units. Using a technique that measures molecular mass through scattered light, they tracked individual particles as they grew. The advance was being able to observe the intermediate steps of a process whose beginning and end are much easier to study.
The components initially form weak, reversible associations. Unstable arrangements can break apart, leaving their components available for further encounters. Certain closed arrangements, however, gain stability through multiple connections. These become intermediate stages from which assembly can proceed. The result is a physically constrained pathway through a huge range of possibilities, without machinery directing the placement of every component, all depending on the relative strengths and weaknesses of chemical bonds.
There is an instructive parallel here with evolution, provided we recognise its limits. Molecular assembly does not involve reproduction, inherited variation and differential reproductive success, so it is not Darwinian evolution. Nevertheless, both expose the weakness of imagining that a complex outcome must arise in one wholly random step. “Trial and error” is useful shorthand: unsuccessful arrangements need not persist, while stable intermediates can support further construction. Neither molecules nor natural selection need to anticipate the eventual result.
A useful analogy is that of a jigsaw puzzle: it is perfectly possible to complete the picture by trying out pieces in turn until one fits, then moving on to another piece. As the puzzle grows the number of possible places to try the next piece increases until eventually the whole picture is complete. This is a vastly different process to the creationist parody of simply shaking up the pieces in the box then checking to see if the puzzle has completed yet. And the process works regardless of the eventual picture.
The relevance to prebiotic chemistry is similarly a matter of principle. This experiment did not recreate the origin of life, and its engineered proteins should not be mistaken for molecules freshly formed on the early Earth. It does, however, illustrate why calculations that ignore chemical interactions and intermediate stages cannot establish that natural assembly is effectively impossible. Whether a particular prebiotic pathway worked requires evidence about its actual chemistry, rather than arithmetic based on an imaginary lottery.
Nor does the fact that researchers engineered the experimental system establish that natural systems require a supernatural engineer. The experiment addresses how suitable components assemble; it does not settle how those components originally arose. Its challenge to creationist rhetoric is more precise: an impressive finished structure need not require an external agent to supervise its construction. Before declaring such assembly impossible, creationists would first need to account for what the molecules actually do.
Why ‘Astronomically Improbable’ Calculations Get Molecular Self-Assembly Wrong. How likely is it that a complex molecular structure could assemble without anyone directing the process? That depends on how assembly actually works. A calculation which assumes that every possible arrangement is equally likely, and that the finished structure must appear in one step, may produce an enormous number. But it describes an imaginary lottery, not necessarily a chemical process.The paper in Nature was accompanied by a news item from Oxford University:
Molecules are not interchangeable lottery balls
Molecules have particular shapes, electrical charges and chemical properties. These influence which interactions occur and how long they last. Consequently, different arrangements are not equally probable. Counting all conceivable combinations without accounting for these differences cannot establish the probability of a particular structure forming.
The structure need not appear all at once
Self-assembly can proceed through intermediate stages. Components join, separate and rearrange, while sufficiently stable structures can provide starting points for further assembly. Calculating the chance of all the components arriving simultaneously in their final positions therefore asks the wrong question.
Weak connections can make assembly more reliable
A connection that can come apart is not necessarily a defect. Reversible interactions allow components to leave unstable arrangements and participate in further encounters. Conversely, several connections acting together can stabilise a particular structure. In the Oxford study, closed arrangements provided relatively stable intermediate stages along the assembly pathway.
‘Trial and error’ is a convenient description of this behaviour, but it does not imply awareness or purpose. Molecules neither recognise mistakes nor know what they are building. Their behaviour follows physical interactions under the conditions around them. Weak bonds are naturally replaced by stronger ones.
Self-assembly and evolution are different processes
Both undermine the assumption that complexity must emerge in a single lucky event, but they should not be confused:
- Molecular self-assembly occurs when components associate into structures through their physical and chemical interactions.
- Darwinian evolution involves heritable variation and differences in reproductive success across generations.
- Abiogenesis concerns the emergence of living systems from non-living chemistry. Self-assembly is relevant to that problem, but self-assembly alone is not life.
What does this experiment establish?
The researchers studied an engineered virus-like particle made from existing proteins. They did not produce life from simple prebiotic ingredients or establish how the first proteins arose. Their work reveals how suitable components can assemble through a restricted set of relatively stable intermediates, despite the many arrangements theoretically available.
This does not mean that every proposed natural assembly process is probable. It means that probability must be assessed using the actual interactions, concentrations, conditions and timescales involved.
The central lesson: an astronomical number of conceivable arrangements is not evidence that natural assembly is astronomically unlikely. A probability calculation must describe the process nature actually uses.
New method reveals how virus particles can build themselves, molecule by molecule
Oxford University researchers have captured the step-by-step assembly of individual virus-like particles, revealing how simple molecular interactions can reliably build these complex biological structures. The results have been published today in Nature.
Understanding how viruses assemble – and what can disrupt this process – could ultimately help researchers design novel antiviral treatments, as well as engineer vaccines and other therapies. The new study provides a molecular-level view of how the protein shells associated with viruses can spontaneously and reliably assemble from their individual components, even when there are thousands of possible ways for these to fit together.
The study found that the process works rather like finding a route through a maze in which only the productive turns lock into place. Protein building blocks initially make weak, reversible connections, allowing unsuccessful arrangements to fall apart and be tried again. But when the proteins form particular closed structures, their multiple connections make them much more stable. These structures act as a small number of molecular waypoints, progressively funnelling an otherwise highly complex process towards the completed particle.
A crucial moment occurs when five larger protein building blocks form a closed pentagonal ring - the first particularly stable structure in the pathway. After this step, fewer protein building blocks are needed to reach each new stable stage, allowing the assembly process to speed up.A virus has to solve an extraordinary construction problem. Its components somehow have to find the right arrangement among a huge number of possibilities, without a blueprint or machinery directing the process. We can now watch what happens molecule by molecule and see the physical rules that make it possible.
Dr Roi Asor, co-lead author
Department of Chemistry and Kavli Institute for Nanoscience Discovery
University of Oxford
Oxford, UK.
Capturing a molecular construction process
Viruses protect their genetic material inside precisely organised protein shells called capsids. These structures can contain tens or even thousands of protein components, yet in many viruses their building blocks spontaneously assemble into the correct shape.
Scientists have studied this process for decades, but observing it directly has proved extremely difficult. Crucial intermediate structures are scarce and often short-lived, meaning that conventional experiments can show researchers what is present before and after assembly without necessarily revealing the molecular steps connecting the two.
The Oxford team tackled this problem using an engineered virus-like particle made from 60 protein units. They combined mass photometry, a technology developed at Oxford that measures the mass of individual molecules by detecting the light they scatter, with a new method for confining individual molecules so that they could be observed continuously. This allowed the team to effectively ‘weigh’ a particle repeatedly as new protein components joined it, revealing its growth step by step.
This method lets us study the assembly process directly, we just take a video!
Dan Loewenthal, so-first author
Department of Chemistry and Kavli Institute for Nanoscience Discovery
University of Oxford
Oxford, UK.
The findings explain how an assembly process with an enormous number of theoretically possible routes can be channelled through a relatively small number of productive stages. They also reveal why the difficult initial step, known as nucleation, is followed by much faster growth once assembly is underway.
The weak interactions give the system room to make mistakes. Most encounters don't have to be successful: the components can separate and try again. But once enough of them come together in the right closed arrangement, the structure becomes stable and assembly can move forward. That combination of trial and error followed by locking in successful structures is what makes the process so reliable.
Dr Roi Asor.
Until now, much of our understanding of how these structures assemble has had to be reconstructed from snapshots or theoretical models. Being able to both quantify the underlying interactions and follow one particle as it grows changes that. We can see the important intermediate structures appear and deduce a detailed model of the construction process.
Professor Philipp Kukura, co-lead author
Department of Chemistry and Kavli Institute for Nanoscience Discovery
University of Oxford
Oxford, UK.
The ability to understand these processes at the molecular level could have important applications in vaccine development and antivirals that disrupt viral assembly.
Dr Jack Tan, co-author
MRC Weatherall Institute of Molecular Medicine and CAMS-Oxford Institute.
Oxford, UK.
Publication:
The important lesson here is that molecular complexity cannot be assessed by counting conceivable arrangements and assuming that nature must try them all with equal probability. Real molecules interact according to their physical and chemical properties. Reversible associations allow unstable arrangements to break apart, while relatively stable intermediates provide routes towards larger structures. What looks impossibly unlikely in a creationist calculation can become entirely explicable once the calculation is replaced by an investigation of the actual process.
This experiment did not recreate the origin of life, nor was it an example of Darwinian evolution occurring in a test tube. It used an engineered protein system to investigate self-assembly. Nevertheless, it exposes a fundamental weakness in arguments which treat natural processes as a single, blind throw of the dice. Neither chemical self-assembly nor evolution requires the finished product to appear in one step, and neither requires foresight. The mechanisms differ, but in both cases the history of intermediate stages matters.
There is also a crucial distinction between explaining how suitable components assemble and explaining how those components originated. The fact that researchers engineered this experimental system does not establish that naturally occurring systems require supernatural engineering; equally, observing its self-assembly does not, by itself, explain the origin of its proteins. A sound scientific argument recognises those limits. Creationist claims of impossibility, however, must also confront the evidence that intricate structures can assemble without anyone supervising the placement of their components.
Once again, science advances by replacing an apparent mystery with a testable account of what happens. Researchers measure interactions, observe intermediate structures and refine their explanations. Invoking an invisible designer contributes no comparable mechanism and makes no contribution to understanding the assembly process. The productive question is not who tells the molecules where to go, but what properties of the molecules explain where they end up.
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