The unfortunate COVID pandemic has provided us with a vivid view of evolution in action. The viral transformation over time associated with the spread of the disease throughout the globe vividly illustrates two concepts: the survival of the fittest and how random mutations can enhance an organism’s capacity to proliferate. In addition, I believe we can learn about a third process by studying the global response to the pandemic which offers another potential evolutionary mechanism.
The mutational evolutionary rationale is that during cell or virus replication, a small percentage of errors occur when RNA or DNA are copied. In such instances, one of the copied genes is not identical with the original. Most of these errors are either damaging or neutral. If the change effect is damaging, the new organism may not survive. Occasionally, however, an error – perhaps, for example, in replication of an outer membrane protein – confers a positive change that may enable the virus in question to spread more effectively and thus infect more people. Moreover, as it is relatively more successful than the non-mutated variant, the survival of the fittest mechanism may eventually cause the mutated variant to replace the non-mutated form.
Given the remote likelihood of a positive random mutation, we might conclude that such a hypothesis is farfetched. However, in appropriate circumstances, highly unlikely chance events are often what nature is all about. In the case of COVID, it is estimated that virus replication takes from 6-8 hours and that between 1 and 100 billion viruses are present during peak infection. Such mass replication makes an originally unreasonable-sounding hypothesis appear more statistically realistic and feasible. A recent COVID related manifestation of this process is the spread of the Delta variant, which, being more contagious than the older form of the disease, proliferated more extensively and so became the dominant COVID form in most of the world.
A closer-to-home example of the significance of statistically unlikely events in nature is human sperm impregnation. Each male ejaculate contains about 100 million sperm cells, of which only one generally combines with the mother’s egg. Each ovary contains about 100 million eggs. This means that the odds of anyone’s being conceived on this planet with their particular genetic makeup is about one in a hundred million multiplied by one in a hundred million – a very small likelihood to say the least. And yet, despite these minuscule odds, here you all are reading this blog! The conclusion is that, under certain circumstances, events that have an infinitesimally small likelihood of ever happening, do nonetheless transpire, and can even occur frequently, as we see by the existence of billions of people living today.
While this theory of random mutations that advance evolution may make sense when one is dealing with a single change that improves an organism’s competitive advantage, the explanation is problematic in more complex circumstances. Even though as we have seen in some instances, small percentages can make a difference, if the statistical likelihood is nevertheless sufficiently low, is change still possible? Here are two situations that call application of this theory into question:
- What happens when an advantageous change requires a series of steps – let us call them A-E – where the intermediary changes (B, C and D) are unstable, and do not confer any advantage upon the organism? How will the organism ever get to step E? This theoretical doubt is scientifically substantiated as paleontologists have found too few examples of intermediary organisms to provide convincing evidence of widespread occurrence of this mechanism.
- What happens when several changes, such as A, B, C and D, must occur simultaneously in order for the advantageous change to come about? One researcher has used the term “irreducibly complex” to describe a situation in which too many simultaneous random mutations would be required for this mechanism to be effective.
There is another problem when one applies the theory of random mutation to explain evolutionary development in advanced organisms.
If we review the history of evolutionary change, we observe that the simplest changes required the most time. Evolution from simple cells to land-based plants and invertebrates (Precambrian) took billions of years; the appearance of land-based vertebrates required 250 million years (Paleozoic) – much less time; herbivores, small mammals, appeared within less than 200 million years (Mesozoic); and finally, our present circumstances took “only” 65 million years (Cenozoic) to evolve. Thus, we can observe that complex changes requiring multiple and coordinated steps occurred much faster than simpler changes, even in living creatures that take decades to replicate rather than hours. If changes are a response to random events, one would expect the opposite – that is, that quick turnaround simpler changes would evolve faster than multiple, complex changes in slower reproducing animals.
Therefore, rather than trying to explain advanced changes by random mutation, we need to look for an additional mechanism for change.
Returning to the present and COVID, while the spread of the virus may be a classic example of how organisms evolve through a series of single mutations, the global response to the virus is not random, and may shed light on a possible additional evolutionary mechanism that could explain the dilemma described above. As we are dealing with government responses to the pandemic, the example I shall provide is conceptual rather than literal.
For purposes of presenting this model, I ask the reader to view a country as a metaphorical organism. If we define an organism as “any organized body or system conceived of being analogous to a living being,” then a country, while not alive, nonetheless shares many of its attributes.
When a country became infected with COVID and enough people became seriously ill or died, it developed a response to the assault. While different countries responded in different ways, each country’s response was deliberate (not random).
Let us take, for example, a country that instituted a policy of social distancing and mask wearing: using the mutation metaphor, changes were instituted. In countries where the sum total of the changes was effective, the influence of the virus decreased, conferring a survival advantage on that country compared to no planned response. Otherwise, the virus continued to proliferate at a higher rate.
What are two main mechanistic differences between a single random mutation that confers an advantage on the organism concerned and a change instituted by a country’s policy?
The first significant dissimilarity is that, in the second case, the changes were not random but deliberate, a calculated strategy. Before introducing change, government advisors analyzed the situation and selected changes they believed would be effective. In terms of (evolutionary) statistics, a deliberate response has a higher likelihood of being effective than a random one. Imagine two situations in which an arrow is shot from a bow with the goal of hitting the bull’s eye. In the first, the arrows are fired randomly in any direction, while in the second, the arrow is aimed at the target. In the second situation, even if the arrow may not initially hit the bull’s eye, it still has a better chance of doing so than an arrow that is not deliberately directed towards the target. Furthermore, with the use of a deliberate feedback loop, further iterative changes based on the arrow’s results may lead to improved aim over time, possibly eventually leading to a bull’s eye. Using computer analogous terminology, the organism’s algorithm was improved over time.
The second difference is that the governmental reaction consisted of more than a single response, as masks and social distancing were introduced simultaneously; two or more coordinated changes are more likely to work effectively than uncoordinated random alterations. Thus, if we use the bow-and-arrow metaphor to explain the response to COVID, a deliberate coordinated action that evaluates the success or failure of an intervention and institutes changes accordingly, has a significantly better chance of responding effectively to the virus than a purely random approach. While an “irreducibly complex” situation may not be able to successfully improve itself through a random process, it is reasonable to presume that it could evolve through a continually planned and coordinated process.
The question that remains is: could some evolutionary processes be goal-directed rather than random? Could some “advisory committee” in the organism institute a change based on an analysis of how to improve that organism’s response to a danger?
Before dismissing this proposition out of hand as unlikely, let us deviate briefly while I illustrate that nature equips advanced organisms to respond to stimuli and threats in a planned and deliberate manner; and to postulate that similarly, a planning factor may enable an organism to evolve rather than merely undergo random change.
If we look at evolutionary development, the most primitive response to a stimulus is an automatic one: a fly, for example, is automatically attracted to a light. A more advanced response is instinct: a series of automatic steps such as what a young animal displays when seeking out the mother’s nipple in order to drink milk (and survive). A further development is the fight or flight response in which an animal reacts to a threat by either fighting or running away. Here we observe the beginnings of choice. The animal performs an analysis of the situation, and somehow “decides” which is the preferred alternative and then acts on it. If the animal’s calculation was correct, it may survive. In due course those animals whose calculations were more successful will remain and dominate. One can presume that advancement and evolution in the calculation process was a key to their survival. As we move up the evolutionary ladder, we find that the capacity for planning and choice in animals broadens: a more advanced animal may be capable of choosing among several alternatives.
If some animals are already endowed with a mechanism that enables them to make potentially sensible directed choices such as fight or flight, could it be similarly possible for those animals to direct their genetic change, as presented conceptually in the bow and arrow metaphor?
After all, nature has a way of using successful mechanisms in multiple situations. As an example, metamorphosis is a phenomenon of nature that is employed by completely dissimilar organisms. A caterpillar turns into a butterfly; tadpoles turn into frogs. Could nature employ a “planning mechanism” not just for a response to danger but also to endow advanced organisms with a directed mechanism of evolution? If so, goal directed evolution could offer an explanation of how advanced organisms have evolved at a faster rate than simple ones.
To summarize: the Coronavirus acts in accordance with Darwin’s assertion that organisms evolve through natural selection as a consequence of random mutations, with the fittest surviving and often replacing the less competitive. In contrast, the various government responses to the virus are deliberate. Can one postulate that, alongside single-mutation evolution among primitive organisms, there exists a complementary evolutionary goal-directed mechanism for advanced organisms which influences genetic evolution?