Evolution is true, but are mutations really random?

Source: Wikimedia Commons.

The evidence is overwhelming that evolution by natural selection is true: organisms change from generation to generation by the accrual of genetic mutations. These mutations are selected for, or against, according to the ability of the resulting organisms to survive and reproduce in their respective ecosystems. A video released by Harvard Medical School a few years ago vividly—if didactically—illustrates the process:

However, an extra idea is often conflated with the foregoing: whereas natural selection is demonstrably not a random process, the mutations underlying the process are consistently assumed to be. The problem is that evidence for natural selection is not evidence for random mutations: nature will select for survival fitness whether the mutations themselves follow a trend or not.

To demonstrate that the genetic mutations underlying evolution are random, one would need a fairly complete record of (a) the mutations themselves, as they occurred throughout the history of life on Earth, including those discarded by natural selection; and (b) the corresponding phenotypic characteristics. Only then could one run a randomness test to verify that no phenotypic trends are present before natural selection plays its role. Of course, the fossil record is far too sparse to allow for such a test.

So the assumption that genetic mutations are random has, strictly speaking, no empirical basis. Its motivation is merely subjective: many cannot fathom any plausible mechanism that could impart a pattern on the mutations themselves. Compelling as this may sound, lack of imagination and a subjective sense of plausibility aren’t valid reasons to pronounce scientific facts.

The spirit of scientific investigation is precisely to look for yet-undiscovered natural patterns, thereby implicitly assuming—if anything—that they, in fact, exist. To affirm, on account of subjective dispositions, that genetic mutations are pattern-less is arguably antithetical to the very spirit of science.

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Moreover, scientific results and speculations have violated our sense of plausibility so often that, by now, we should have learned to be cautious about it. For instance, when compared to the hypothesis—seriously pushed by many physicists to explain the bizarre fine-tuning of universal constants—of countless parallel universes, for which there is no shred of empirical evidence, the possibility of an inherent natural bias underlying genetic mutations doesn’t seem so absurd to this commentator.

In an attempt to be more objective, one could argue that genetic mutations are quantum-level events, which have been demonstrated to be inherently random. But since the hypothetical trends in question are phenotypic—that is, biases towards certain body structures, functions or capabilities—they necessarily entail many quantum events. At such a compound level, global patterns across events can be consistent with individual events meeting randomness criteria. Let me illustrate this with a simple analogy.

Imagine that you toss three dice on a table, multiple times. After each toss, you inspect each die separately and verify that they randomly display a number from one to six. But when you look at all three dice together, you realize that either they all display an even number or they all display an odd number. The resulting global pattern not only clearly violates randomness, but is also constituted by individual events that, when inspected in isolation, meet randomness criteria. Therefore, that individual quantum events are random doesn’t preclude the possibility of non-random global mutation patterns.

Indeed, the possibility of there being global patterns of behavior in nature that transcend locality restrictions is opened up by quantum mechanics itself. In the words of physicist Erich Joos, “Because of the non-local properties of quantum states, a consistent description of some phenomenon in quantum terms must finally include the entire universe.”

Moreover, although physicists can test individual quantum events in the laboratory and verify that they are random, it is impossible to discern a global pattern within the complexity of the physical world at large; there are just too many ‘dice’ to keep track of under controlled conditions. So for all we know and even can know, genetic mutations may follow yet-unrecognized phenotypic trends operating non-locally across mutation events.

As a matter of fact, there are empirical suggestions of fundamental natural regularities—‘laws of nature’—irreducible to microscopic events. If so, such a precedent should compel one to avoid outright discarding, on the basis of mere intuition, the possibility of unknown macroscopic laws biasing the genetic mutations that drive evolution.

Finally, one could argue that we don’t need anything other than random mutations to explain the variety of life, so that postulating a pattern prior to natural selection would violate Occam’s proverbial razor. But we don’t really know that randomness is enough, do we? The only way to verify it would be to run a quantum-level simulation of the evolution of life to see if, with trendless genetic mutations as input, we could reproduce the biological variety empirically observed. Such simulation is, of course, impossible. Only toy models are feasible, but these aren’t representative of the complex reality we are trying to understand. If anything, the amazing richness of life seems to suggest precisely a natural bias in that direction.

Notice that I am not claiming that such bias exists; I don’t know it either way, this being precisely my point. I am simply pointing out that the hypothesis cannot be discarded. Moreover, I am not hypothesizing any deliberate intervention in natural affairs by some supernatural agency. I am simply raising the possibility of yet-unrecognized but natural regularities, which impart trends on genetic mutations. Nothing we know today precludes this possibility.

I also acknowledge that, to many, the hypothesis of an irreducible phenotypic bias feels so implausible as to be ignorable. There is nothing wrong with holding such an opinion. But passing opinion for established truth is a problem, for if we make an exception to the scientific practice of separating subjective views from objective facts, we open Pandora’s proverbial box.

The very notion of ‘randomness’ is already loaded and ambiguous to begin with: although it is defined as the absence of discernible patterns, theoretically any pattern can be produced by a truly random process; the associated probability may be vanishingly small, but it isn’t zero. So the claim that a natural process is random not only amounts to little more than an acknowledgement of causal ignorance, it can also be construed so as to be unfalsifiable.

On top of such inherent problems, today the idea of random mutations has become so intertwined with that of evolution by natural selection that, remarkably, the overwhelming empirical evidence for the latter is implicitly misconstrued to be evidence for the former. This is a serious inaccuracy, for there is arguably no other natural process as relevant to us as the nature of life.

If anything deserves the full rigor of interpretation required by the scientific method, it is the evolutionary mechanisms that produced us humans. Humbly acknowledging what we do not know about them is imperative, lest we arbitrarily eliminate interesting avenues of investigation.