Most people readily admit that they don’t understand Quantum Theory (QT). QT is not in the news much. When it is, the story is about some arcane effect (superposition, entanglement) that even physicists can’t reconcile with their everyday experiences. There is no shame in admitting “ I do not understand QT”. Ask people if they have an “opinion” on QT and you will not get much of an answer.
Evolution is different. If asked what their opinion is about the Theory of Evolution (TOE) most folks will be happy to tell you why they do or don’t “believe” in it. Why this difference about key theories that are the bases of their respective fields of science?
As we will see, the TOE based on seemingly easy-to-understand concepts (although they are most often misunderstood). As the TOE is basic to all of our understanding of biology it is frequently in the news. Unlike QT, the TOE deals with a subject that all Western religions discuss.
In truth, most people no more understand the TOE, how it operates, and what its implications are than they do QT. It just seems more accessible and people “believe” that they understand it. Here I will present an easy to understand synopsis of the TOE. I will return to important elements in future posts, in particular whether the statements “I believe” and “I don’t believe” in the TOE actually make any sense.
First, a reminder about the meaning of “theory”. A theory is not a hypothesis. It is not an idea. It is a well-founded and supported statement about nature that has withstood many challenges. It is a theory, and not a fact, because, as discussed in earlier posts, science deals only with observations and all explanations of these observations forever remain subject to revision. The TOE is no less proven than is Einstein’s relativity-derived equation E=MC2, despite the proof of the later provided by the destruction of Hiroshima and Nagasaki, brought about by the conversion of a small amount of mass into an enormous amount of energy.
I will first present a short and simple overview of the TOE. Then, and in subsequent posts, I will discuss this in more detail, especially why it is to Biology as General Relativity and QT are to Physics, and what it’s implications are. It is the implications of the TOE that trouble so many because they contradict the truths (actually beliefs) that we have been brought up with.
The TOE
The TOE is based on two simple ideas. The first, variation, is the fact that all species display biological variations. Variation is obviously true. We observe it every day in every way we perceive. The second idea is selection. Selection is obviously true as well. A deer that is slightly slower than its peers is more likely to become a lion’s lunch. In truth, selection is a more complicated concept than variation and is more often misunderstood.
Variation
Variations occur in all species in nature. Some variation is a result of their lived experience, i.e. what is often called “nurture”. A pine tree seed that lands and grows just below the mountain tree-line is destined to be short, while a seed from the same species ( and with the same genetic endowment) that lands and grows on the mountains’ lower slopes will grow much taller. Other variation is inherent, i.e. a result of the inheritance of the individual as transmitted from its parents by way of its genes. This is obviously and indisputably true. Two tomato plants of the same species and even same variety, planted side-by-side in your garden, will grow into plants that are of different size and shape and will produce a different amount of tomatoes.
People have taken advantage of the variation inherent in species for thousands of years. Dogs, all descendants from wolves, vary enormously in so may ways. Most varieties of dogs have been willfully produced by selective breeding over the past 200 years of so. Most of the plants and animals that we depend on for food differ greatly from their wild counterparts. Neither the corn we grow for human consumption, nor the corn we grow to feed the animals we eat, resembles teosinte, the wild-grass progenitor of all corn varieties. Likewise, the wild progenitors of wheat, rice, chickens etc. are much less productive then the versions we grow for consumption. Most of these alterations are the results of selective breeding by humans beginning at the dawn of agriculture. This process continues today. The young girl who exhibits her prize cow and wins the 4H medal succeeds not only by providing good care and nutrition, but also because her prized cow’s parents were carefully selected.
Since the early 1970’s we have learned how to manipulate genes directly. By doing so we have shown that genes transmit all sorts of characteristics. Some types of genetic inheritance are complex and involve the small contributions of many genes. As of 2017 at least 700 genes have been shown to contribute to attained height in humans. That is one of the reasons why we cannot precisely predict the attained height of children based on the height of their parents; their children inherit an assortment of gene variants, half from mother and half from father. Without DNA sequencing both parents and the child we do not know which variants were inherited by the child, even if we did know the actual contribution of each variant to attained height. It also brings up the issue of the gene-environment interaction, a topic for another day.
Selection
Charles Darwin, the more important of the two scientists who nearly simultaneously developed theories of evolution, coined the term “natural selection”. Darwin understood that plants and animals produce many more offspring than could (or should) survive. The offspring struggle to survive against one another, against their competitors that belong to different species (but which make use of similar resources), and against the stochastic events of their lives (i.e. luck). In this struggle, anything that provides an individual with a survival advantage, however so slight, will increase it’s chance of survival. Over time, the characteristics that favor survival under the prevailing circumstances will become more common, and those that work against it less common. Darwin called this “natural” selection in order to differentiate it from the purposeful selection that man partakes of when breeding desired characteristics into plants and animals. He recognized, of course, that the similarity between these two situations are more important than the differences, i.e, they both involve selection. When man engages in animal husbandry, or plant breeding, the forces of selection (which evolutionary biologists term “selective pressure”) comes from man himself. For “Natural Selection”, nature provides the selective pressure. In Natural Selection, there is also an element of luck involved. Natural selection involves so many individuals (at least as compared to selection carried out purposefully by man) that much of the luck (but certainly not all) get’s canceled out.
Given these two “forces”, variation and selection, evolution is inevitable. Our pets are the result of it. Our food supply too. We ourselves too. Evolution can even be carried out in the laboratory. For example, if we set up a method of inducing variation in a protein by forcing the creation of artificial mutations, and select protein variants with particular characteristics, i.e. we can “evolve” the protein to a form that differs substantially from the original. Evolution can be used to improve the function of computer programs. Evolution can even be demonstrated to young children in a classroom. When teaching my (then) young son’s 6th grade class I started by passing around a bowl with an equal amount of chocolate and licorice candies. I instructed the students to take one (and only one) candy that they preferred. The two types of candies can be considered two different species, and the children were the predators. Their preference was the “selective pressure” and was acting on the characteristic of “taste” that was inherent to the candies. When the bowl eventually returned to me, unsurprisingly, more licorice than chocolate candies had survived predation. Unfortunately the demonstration ended there because candies cannot reproduce. This classroom demonstration is not as far from nature as one might first think. Monarch butterfly caterpillars eat milkweed, a poisonous plant. The poison (analogous to the licorice in the classroom demonstration) protects the monarchs (candies) from predation by birds (children). It is easy to imagine how, over time, milkweed became a favored food of successful monarch butterflies.
Darwin made use of a second term to refer to the process of selection although he attributed the term “survival of the fittest” to Herbert Spencer. Both “natural selection” and “survival of the fittest” well describe the process by which individuals, bearing characteristics that provide them with a survival (or reproductive) advantage, become more numerous under the influence of a process that leads to the destruction of many, or most, of the individuals who are born. Unfortunately, the term “survival of the fittest” has led to gross misunderstanding that persists and will be the subject of my next post. For now, let me simply say that terms such as survival of the fittest, and “Nature is red in both tooth and claw” (Alfred Lord Tennyson’s In Memoriam A. H. H., 1850) lead many to believe that all animals are only out for themselves and selection can only work to prevent death by violence. With this as a foundational misconception the problem of selection for characteristics such as altruism becomes manifest.
In earlier posts I asked why science causes so much controversy. Evolution is the “poster boy” for this question. I have shown that the TOE is based on two simple ideas, variation and selection, and that neither is deniable. I have explained that given variation and selection, evolution is inevitable.
So why is the TOE controversial? In truth it is not the TOE that is controversial but rather the inevitable conclusions that must be drawn from it. If species evolve by selection then they were not created in their current forms. Biology has shown that all forms of life on Earth are closely related. For example, protein biology is shared by all Earthlings. So too the genetic code (with minor exceptions). If all species are closely related yet evolving then it follows that we have all evolved from an early form of life. This, of course, contradicts the myths that many have been taught from childhood. For those that take the Jewish Torah literally (including many Christian and Moslem sects), all species, including man, were created as is. The only way to account for the astounding amount of evidence that this is not so, and that the Earth is not, just a bit less than 6,000 years old (for example fossils of no-longer extant animals), one must resort to claiming that God intended to fool us, a bizarre concept if there ever was one.
I will end this post with one more observation. We make use of evolution to improve our food. We fight to survive evolution when bacteria develop resistance to our antibiotics. We can make evolution occur in the laboratory. We can use it to produce better computer programs. When our bodies encounter a pathogen our immune cells use a process of evolution to improve the antibodies we make until they are good enough to cure us and protect us from future encounters with the same pathogen. So is the process of evolution a theory or an observation and as much a “fact” as any other observation we make? The “theory” in the TOE is the concept that, given that evolution occurs, and that all life on earth is demonstrably closely related, that all life is descended from one progenitor by a long process of differentiation and selection. This concept is what troubles people who prefer to believe a story for which there is no, and can be no proof (other than a “revelation”). To reject the TOE is to accept evolution when we need or want it, but reject it when we are troubled by it. The alternative is to question ancient myths that contradict what we can demonstrate to be true. But wait, you say, don’t people who reject evolution do so on the alter of rejecting hypocrisy? To put it another way, since I believe that the Torah is literally true must I not then reject the TOE if I am not to be a hypocrite? Or, is there a “way out” so that I can maintain my religious belief and accept science too? I will return to this important question my next post on this topic.