By Mike Gene

There is a very simple explanation that is widely accepted to explain evolution change:

It is this thinking which allows many to extrapolate small evolutionary changes that are observed (microevolution) to rather large evolutionary changes (macroevolution). Thus, we can explain the later in terms of the former simply by adding enough time.

For example, we have observed bacteria undergoing minor sequence changes that give rise to antibiotic-resistance. This, along with many other observations, allow us to document that random mutations and natural selection (RM&NS) are responsible for at least some evolutionary change. Now, if we turn to the realm of the unobservable, we have good indirect evidence that birds and mammals evolved from reptiles. This would entail, among other things, the transformation of reptilian jawbones into the mammalian earbones and reptilian lungs into avian lungs. Since such transformations did not take place over a short period of time, it only makes sense to extrapolate the evolutionary mechanisms we have observed in bacteria to the origin of mammals and birds.

What's more, not only can we argue this extrapolation is reasonable, but we can also argue that is not reasonable to deny it. How? We could point to the scientific explanations for the formation of things like stars and mountains over great periods of time. Such explanations are extrapolated from the relatively small effects we see on over short time scales. If we accept (1) to explain the origin of stars and mountains, why arbitrarily exclude life and evolution from such reality?

Since this whole argument is one of extrapolation, let's first consider whether such extrapolations are justified and then focus on the two basic forms of extrapolation: a. stars and mountains to life and evolution and; b. observable evolutionary changes to unobservable evolutionary changes.

It is a known fact that small change + much time does not always equal large change. Consider a couple of obvious examples. Let's say that you decide to create a pile of coins at a rate of one coin added/day. After one week, you'll have a pile seven coins high. From this small scale perspective, you then argue that after 10 years of adding coins, you'll have a pile 3,650 coins high. But we all know, from experience, that the laws of physics will eventually step in as the tower of coins becomes unstable at some point and comes crashing to the ground long before we reach the 3,650 number.

Consider a biological example. Jones begins to lift weights and starts by bench pressing 100 pounds. After one week, he'd up to 110 pounds. After 2 weeks, he's pressing 120 pounds. He then uses formula (1) and predicts that after 2 years of working out, he'd be benching pressing 1140 pounds. Of course, we also know from experience, that the constraints of anatomy and physiology step in and will prevent Jones from ever bench pressing so much weight.

These two simple examples demonstrate that (1) is not always true, thus cannot be used as an axiom. One might argue that we can use (1) as an axiom as long as we have no knowledge of any limitations that may come into play. Perhaps, but if we try to secure this argument for evolutionary change, we end up merely assuming there are no relevant limitations. Do we really know enough about ontogeny and phylogeny to justify this raw assumption?

But what if we accept (1) to account for the origin of stars and mountains? Are we then engaged in special pleading when exempting biotic systems from the same explanatory schemes? I do not think so for the simple reason that both stars and mountains are not analogous to biotic systems. They differ in two fundamental ways.

Structural differences. Imagine we invent a new machine called the "Expander." The Expander works as follows: material that is placed inside the Expander is magnified in size, i.e., it expands to becomes many times larger than the original. Now, if we cut off a small piece of the Sun or a small piece from a mountain, and place it in the Expander, we could essentially generate a new sun or mountain. This is because both the Sun and mountains can be viewed as "aggregates," where a mass of parts are loosely associated with each other in an unorganized fashion. But if we were to take a chunk of skin from a mouse and put it in the Expander, we would not generate a new mouse. This is because a mouse is not truly an aggregate, but instead of composed of many different parts that are tightly organized. While it seems perfectly reasonable to view aggregates in terms of (1), given that expansion/enlargement lend themselves nicely to such process, it is not clear at all that biotic organization follows suit.

Formational differences. Middle ear bones and avian lungs form as the result of a genetic program which, in turn, is run by encoded instructions deciphered by nanomachines. Stars and mountains are not built by nanomachines or encoded instructions.

Thus, when we consider that both the structural complexity and the formation of stars/mountains differ significantly from that of living organisms, acceptance of (1) in the former cases does not automatically entail we accept it in the later case.

There are at least two reasons to think (1) is a flawed explanation of evolutionary change. That is, while (1) may apply to some evolutionary changes, generalizing such phenomena to the level of a universal explanation of evolution is an unjustified step.

First, it is well-known that small genetic changes over small periods of time can lead to large morphological changes. Unfortunately, most of the observed examples of such change are clearly deleterious. Yet a significant number of biologists throughout the years have proposed such "macromutations" to explain various evolutionary transitions. In fact, many developmental biologists propose just such changes to explain various evolutionary transitions. And that takes us back to the origin of the vertebrate middle ear. Most developmental biologists would attribute the ear-bone evolution to developmental regulatory changes. That is, no new material was/is employed. Instead, the same old material was simply reshaped. And this could occur because of changes in the timing of expression of certain genes. Yet such regulatory/timing schemes seem largely irrelevant to other forms of change associated with evolution, such as the origin of novel molecular machines. Proteins do not change because of the time when they are expressed. To change a protein, you need to change the amino acid sequence. To create a new molecular machine, we need to account for the various parts without the help of a developmental program. Thus, unlike the ear-bones, evolution of the cellular systems involve changing the material and coming up with new material.

I think this is a crucial point. More and more biologists are arguing that morphological evolution is driven by changes in regulatory elements. In fact, some have even proposed that alterations in the patterns of gene regulation have been far more important in evolution than changes in protein function. But what does this mean? It would mean that all of the fossil evidence is largely the consequence of trivial evolutionary events that have little meaning for the origin of much cellular machinery. If most of evolution and the fossil record can be explained by changing the pattern of gene expression, then most of evolution and the fossil record is not relevant to questions about the origin of those genes or the basic process of gene expression itself. (1) might be vindicated at the level of organismic evolution, but at a very high price. That price being that almost all of the evidence of evolution now becomes irrelevant to the deeper aspects of life.

Let me put it another way. If much/all of morphological evolution can be explained with little/no change in the basic biochemistry and cell plans of organisms, then that morphological evolution, which depends on that basic biochemistry and cell biology, does not apply at this level, but instead exists only because it is built upon this level. While evolutionary hypotheses that build upon (1) also build on what biochemistry and cell biology provide for evolutionary tinkering, they don't explain the origin of that biochemistry and cell biology themselves. To put it one way, the evolution of clothing and fashion depends on the human body, but nothing about fashion-evolution explains the origin of the human body.

Secondly, our thinking of evolution is often skewed by our interest in our own origin. Thus, we focus on the evolution of some primitive vertebrate, then fish, then amphibian, then reptile, then mammal, and finally human. And this is a story of significant change involving a gradual increase in complexity. But is this really typical of evolution? Ought we not also consider the bacteria, which comprise 50% of the planet's biomass? Bacteria have also been around for billions or years and have the shortest generation times of all living organisms. Yet when we consider bacteria, (1) breaks down. Thanks to bacterial genomics, it is now becoming quite clear that extant bacteria would not be all that different from the last common ancestor of bacteria, which is to say that 3.5 billion years of small changes in bacteria have not resulted in any obvious large change. In terms of overall complexity, modern bacteria are no more complex than their 3.5 billion-old ancestors. In terms of the basic cellular machinery, not much has changed. Many small changes have not added up to large changes. Might this be the typical way in which evolution works?

If one desires to extrapolate small changes into large changes by simply adding time, one requires independent evidence to justify this move. The problem is that we really don't know how evolution occurs. And when talking about the evolution of the mammalian middle ear bones, we should not forget that we are still basically in the dark in trying to explain how both a mammalian and reptilian zygote actually develops the middle ear and jaw bones, respectively. Without this knowledge, attempts to explain such a transition as a function of a series of small, incremental changes stretched across time are rooted in ignorance. That is, we don't truly understand neither the process of development nor the process of evolution and without such knowledge, there is no reason to think we are on safe ground when employing (1).

Attempts to justify this move by appealing to the use of (1) in astronomy and geology fail because biotic complexity differs in both structure and formation.

One may assume (1) to explain evolutionary change as a working hypothesis, but we should keep in mind that large changes in evolution are basically a "black box" and a series of small incremental changes may play only a trivial, fine-tuning role in any transition (there is no evidence to think otherwise). What's more, bacteria, as the predominant life forms on this planet, which have experience the most evolution of all life forms, tell us clearly that (1) need not apply to biological evolution.

In the end, appeals to small change + deep time are embraced merely as a matter of convenience, as it happens to be the primary way we can think about evolution at a time when we are just starting to come to grips with it. As we begin to better understand the process of evolution, I predict (1) will one day be viewed as a quaint understanding that served mostly to highlight just how much we didn't understand evolution.