In the previous entry in this series “Survival, Success, and Significance”, we discussed how abstract notions of human success, could become chained to the lower level survival, of the animal body. The big takeaway, was that higher levels of abstraction, can effectively be connected to lower levels, through the process of evolution. We saw that evolution creates special kinds of “links”, that emerge as correlations between different states of a system, in time. Crucially, we explored the realization that although these correlations may appear causal and intentional in retrospect, they do not require any intentional and intelligent “designer”, as far as we can tell.
In this entry, we will start to take a closer look at this mysterious process, of creation and destruction, that is foundational to this whole series, and indeed, for life itself. That one idea that has explained so much, and angered so many. A concept so wonderfully simple, that you could explain it to a curious 5-year-old. An idea so complex and vexing, that you could spend lifetimes enumerating its surprising implications.
We call it “Evolution”.
What is Evolution?
Among all the ideas that have ever emerged from a human mind, the concept of evolution, might be the most transformative. There is so much that can be said about evolution, and much more that is still yet to be understood. These are big and important topics, that require much more time and detail, than can be adequately provided in this compressed format. That said, what, I think, can be done, and what we will attempt to do, is to get an overview, of some of the most essential aspects of the topic. The expectation here, should not be that one could become a contributing expert to the field of evolutionary biology, from merely reading these few pages about the topic, at a summary overview level. Instead, the aim and the attitude, should be to transition from being something of a lost layman on the topic of evolution, and to become more of an informed observer. Someone who knows enough to at least ask meaningful questions, to learn more beyond this short treatment, and to avoid some of the most common and regrettable logical fallacies, still plaguing the topic of evolution to this day.
“As many more individuals of each species are born than can possibly survive; and as, consequently, there is a frequently recurring struggle for existence, it follows that any being, if it vary however slightly in any manner profitable to itself, under the complex and sometimes varying conditions of life, will have a better chance of surviving, and thus be naturally selected. From the strong principle of inheritance, any selected variety will tend to propagate its new and modified form.” ― Charles Darwin, The Origin of Species
In the year 1859, Charles Darwin published the first version of “The Origin of Species”. This collection of writings, represented strands of thinking, that had been with him for quite some time. They stemmed from a question and an intuition, spawned years before, when Darwin returned from his voyage on the HMS Beagle, in 1837.
The primary mystery which motivated Darwin, and racked his brain for decades, was seemingly simple, and yet oddly unreachable, at the same time.
How, and why, do diverse species come to exist, all over the planet?
The default answer most widely accepted by the masses, was that a creator god, used intelligent design, to populate the world, to his liking. Clearly this is not the kind of answer that would satisfy a mind like Darwin, but the answers were not at all obvious. How does one make progress on such a grandiose topic of investigation, while the tools for studying questions of biology were still nascent, and in many cases non-existent?
It turned out that a combination of piercing intuition, dogged determination, and careful, often painstaking investigation, was enough to put a crack in the seemingly impenetrable barrier. The wall between the human mind, and the secrets of nature’s wonders, would not be blown apart by TNT. Instead, it would be chipped away, bit by bit, like a prisoner digging out of jail, with a spoon.
The route that Darwin took to get to his revolutionary theory, was fittingly unexpected, and very clever.
Selection by Human Breeders
Though Darwin did not believe in a world governed by the intelligent design of a creator god, he certainly could appreciate the role of intelligent selection, in the domestication of animals, by humans.
One of the biggest and most insurmountable problems in any scientific line of inquiry, is the issue of having access to sufficient observable data, to base hypotheses on, and to falsify them.
In some cases, such as when it comes to studying the moon or other celestial bodies, space, i.e., distance, is a main barrier. In other cases, as in the case of studying the origin of species, time becomes a barrier as well. How can a person study a theory about variations and selections, leading to new species, without being able to have confidence that variations and selections are actually what is influencing the observed outcomes? Further, how in the lifespan of a single human, would someone ever be able to witness enough generations of sufficient animal species, coming and going, to be able to say anything conclusive, based on such a small amount of time?
The key, for Darwin, was to use the human directed, domestication of animals, as a living laboratory of sorts. Here we could actually know something definitive about what was happening. Whether someone believed that god created life, or even the first version of each species, we could verify that humans certainly domesticated animals, and purposely changed them, through selective breeding.
He noticed that humans, through the process of selective breeding, have been able to effectively change some species of animals in dramatic ways. Dogs might be the best example of how much intelligent selection, by humans, can accomplish. Many dog breeds, are essentially man made creations. This is true in the sense that certain traits were selected by humans, among the variations within a given population. Those selected traits were then effectively amplified, by a reinforcing feedback loop, that pushed selected traits, into the next generation, by selectively breeding certain animals for that reason.
In this way, human breeders were able to change species significantly, via directed selection. The challenge for Darwin, would be to show that this kind of change, could take place in nature, without the guiding reason of god, or the profit seeking motives of man.
It has often been assumed that man has chosen for domestication animals and plants having an extraordinary inherent tendency to vary, and likewise to withstand diverse climates. I do not dispute that these capacities have added largely to the value of most of our domesticated productions: but how could a savage possibly know, when he first tamed an animal, whether it would vary in succeeding generations, and whether it would endure other climates? ― Charles Darwin, The Origin of Species
The prospect of creating a naturalist account for the origin of species, is much smoother and linear in retrospect, than it was in real time. The phrase “hindsight is 20/20” could not be more apt in this case.
It might seem obvious that animals, even of the same species, and even of the same parental lineage, vary in some regard, no matter how slightly. This, I think, was also well observed, if not entirely understood, by minds long predating Charles Darwin.
The issue with variation, is not a matter of if it happens, but why it happens, and to what degree. Further, as shown in the quote above, there was an assumption that humans had somehow specifically chosen to domesticate only those species that possessed the desired amount of variance, as some inherent aspect of their nature. This line of thinking tends towards the impression, that the examples of variance and selection under human directed breeding, should not be thought of as comparable to variance in the natural world. If this was shown to be true, then the journey to find a naturalist account for the origin of species, would become radically more difficult, if not practically impossible (at least with 19th century science and technology).
So, the challenge was to show that variance, even among closely related animals of the same species, was not merely an innate quirk, of certain species that man had fortuitously decided to domesticate. One needed to find evidence, that variance of at least a similar character, to that of domesticated animals, did, in fact, occur in nature, ubiquitously.
Again, it is worth noting just how contentious this issue of natural variance was. There was, it seemed, staunch opposition to the thought that nature itself could stray from a straight trajectory. Either for religious reasons, or perhaps in some cases, just lack of imagination, this bias against natural variance, was a large impediment for people like Darwin, who were trying to see things differently.
The doctrine of the origin of our several domestic races from several aboriginal stocks, has been carried to an absurd extreme by some authors. They believe that every race which breeds true, let the distinctive characters be ever so slight, has had its wild prototype. At this rate there must have existed at least a score of species of wild cattle, as many sheep, and several goats, in Europe alone, and several even within Great Britain. One author believes that there formerly existed eleven wild species of sheep peculiar to Great Britain!― Charles Darwin, The Origin of Species
Another issue that becomes very apparent when reading from Darwin’s own writing, is that there was not just one, but several conceptual hurdles, that could seem logical at first glance, but in hindsight, seem to be mirages.
One example that seems worth noting, is this erroneous idea of some of Darwin’s contemporaries, that crossbreeding animals, was akin to mixing blue and red marbles into the same bowl. If you think of the marbles compared to a painter's palette, you can see the problem. No matter how many blue and red marbles you mix into a bowl, you will never get purple. In contrast, a painter may take small swatches of many different pigments, to blend as he or she sees fit. Now it’s clear, at least in the present day, that past a certain point,1 evolution cannot be quite as free as a painter. At the same time, it is also clear that nature has more freedom in its creative powers, than merely mixing marbles in a bowl. It’s as if people thought that the rules for biology, were so limited and precise, that any apparent divergence was somehow evidence of a new original creation in the past.
It has often been loosely said that all our races of dogs have been produced by the crossing of a few aboriginal species; but by crossing we can only get forms in some degree intermediate between their parents; and if we account for our several domestic races by this process, we must admit the former existence of the most extreme forms, as the Italian greyhound, bloodhound, bulldog, etc, in the wild state. ― Charles Darwin, The Origin of Species
In other words, many people believed that all nature could do, was to mix the blue marbles of one parent, with the red marbles of the other. The implication is that for something like an English Bulldog, the traits that define the breed, could never be new developments of nature, after some original creation. By this line of thinking, the muscular stocky stature of the Bulldog, and the flattened face and underbite, were to be thought of as different colored marbles that had to exist previously, as part of original creatures with those traits. Further, this also suggests that the traits of species cannot vary from one generation to another. Again, it’s as if, each animal was only given certain traits in the form of pre-existing colors of marbles, and could never start with say, a red trait and blue trait, and then get a green output. One gets the sense from such a perspective, that every appearance of a novel trait, is indicative of a new and unexplainable origin of a species.
The point Darwin is making in his quote shown above, is effectively appealing to the principle of parsimony, in terms of the explanations we use to describe the world. If the origin of each species, even those differing by only the slightest amount, requires a new miracle each time, then it seems we are heading in the wrong direction. More commonly, this kind of approach is often tagged as “Occam’s Razor”. The idea that generally speaking, the simplest explanation, that requires the least number of assumptions and logical leaps, is frequently the best one.
If you seriously consider this logic about each species requiring a separate miraculous creation event, the problems multiply rapidly. For if you extend it even within confined geographical regions, you are led to conclude that there must be unexplainable new creations of species all over the place. Further, they must also occur throughout the history of life on this planet, and continue through the present day, as variation has not ceased. This is the conundrum we face, if nature cannot accomplish this degree of variation, via natural processes.
This is some of the thinking that Darwin was up against, regarding natural variation, and the origin of species in general.
The key to gaining some insight into variation in nature, from the variation witnessed in domesticated breeding, was to understand what was actually being controlled by humans, and what was not.
It may seem at first glance that humans were controlling the traits of domesticated animals, but this control was only at the coarse grained level, and only indirect at best. A breeder may try incessantly to create Oxen with muscular bodies that appeared to be chiseled out of granite, and that posses an endless endurance for work, in the relevant climate. He may desire these traits to maximize his ability to plow his fields for profit. The issue is that regardless of what the breeder may desire, he cannot order this up, as if placing a call to a personal chef, who can prepare any meal under the sun. In the case of human directed breeding, the humans only exert control over the high-level inputs, i.e., the parents who create the next generation. What humans could not control, especially before the science and technology of genome sequencing and manipulation, is to specify precisely how the code representing the next generation, should be altered, tweaked, or expressed.
Under domestication, it may be truly said that the whole organisation becomes in some degree plastic. But the variability, which we almost universally meet with in our domestic productions, is not directly produced, as Hooker and Asa Gray have well remarked, by man; he can neither originate varieties, nor prevent their occurrence; he can preserve and accumulate such as do occur. ― Charles Darwin, The Origin of Species
The result of these issues of accounting for variance, is that it was much more difficult, to vault over the hurdles, to a theory of natural selection, than we might otherwise appreciate from our modern vantage point. That said, Darwin was eventually able to see through the artificial process of human selected breeding, to something real and natural, beyond human control. The random variation that manifested itself in each new animal, is perhaps nature’s ultimate show of force, that try as we might, there would always be an element beyond our top down control. Paradoxically, it is only because of this natural variation, the human directed breeding, can work in the first place.
So, if variation would remain wild and uncontrollable under human selection, then there could be no doubt, that variation existed in the wild, beyond the confines of human aims.
This set the stage for Darwin’s great insight, that species could originate from natural selection.
In this entry, we looked into the question of “what is evolution”, from the standpoint of Charles Darwin himself. Several quotes were used from the actual book “The Origin of Species”, so that at least some of Darwin’s insight, could come through in his own words.
We learned that Darwin, did not make a beeline to his theory of evolution, in a single “eureka moment”. Perhaps more fittingly, the theory of evolution itself, evolved. Starting with a focus on human breeders of domesticated animals, Darwin observed the power of selection. Variation was eventually understood to be something that was not directly controllable by humans. Instead, it was in effect the rebellious Dionysian side of nature, that would not submit to the Apollonian style order, humans might like to impose. This meant that variation, was in essence fundamentally “wild”, and thus, nature would produce variation, outside the confines of human intervention.
Looking forward to the next entry, we will explore the linchpin of Darwin’s insight, the idea of evolution by natural selection.
- Although it is beyond the scope of the current entry, it is at least worth mentioning something about limitations on evolution. In particular, just as one can think of the history of evolution as a tree in time, with branches for each species, one can use a similar metaphor for paths in genotype space and phenotype space. The point being, that there are some paths in evolution, that once taken beyond a certain point, cannot merge or mix with other branches, in a non destructive way. So with the comparison of evolution to mixing marbles, versus a painter mixing colors, we start to see that evolution is somewhere between the two extremes. There are times perhaps at the very early stages of an evolutionary branch, that recombination of close branches may still be possible. So this would be akin to a painter mixing shades rather close in appearance. At other times, say with something like dogs and birds, there is such great divergence, that no amount of mixing will create a coherent combination of the two. This would be more akin to a bowl of blue and red marbles, which in contrast to the painter’s palette, can never produce a true mix of purple. ↩︎