I know it might seem like I have a theme going, but it’s unintentional; the book lineup just kind of fell together. Nonetheless, the progression is actually interesting. Previously, I reviewed Why Evolution Works (and Creationism Fails), which was tailored to addressing the attacks on evolution by creationists, thus not a reference suited towards a full explanation of the evolutionary process. This was followed by Your Inner Fish, which gave a tremendous amount of evidence that we know evolution has occurred (and the fascinating details therein,) but didn’t address how the selection process works. Stepping up to the plate now is Jerry A. Coyne’s Why Evolution Is True, which details both the evidence and the process, and points out how creationism fails to explain the evidence while it’s doing so.
If you’re familiar with Coyne’s website of the same name as the book, you know his writing is readable, direct, and smooth – he doesn’t write for fellow scientists, but for the general public, and does a good job of it. The book is no different, and is easily grasped by adolescents and onward. Like his colleague Neil Shubin (they both teach at the University of Chicago,) Coyne is an educator, and aims for as broad an audience as possible without excluding anyone. Briefly, I caught some sections early on where just a little biological jargon slips in without explanation, but this occurs only once and doesn’t detract significantly from the passages – otherwise he manages to reach practically all readers and keep them interested with direct prose and excellent flow.
Coyne is careful to detail the genetic processes themselves, which provide the primary function of evolutionary change and speciation, showing how such variations crop up in individuals, and how these incorporate into an entire species. He also addresses the timelines, and how long changes can take, showing that we have had more than enough time to see the changes that we have. And he shows the various selection processes themselves, explaining how different factors produce change in different ways. His explanation of sexual selection and the production of traits that should be detrimental to survival, such as flamboyant peacock tails, shows why it still makes sense, highlighting the undirected and goal-bereft process that yet provides benefit to the species. He makes it clear that selection produces “better,” not “best,” and relates only to passing genetic traits to offspring, not necessarily living to a ripe old age.
The book is honest, and admits to a few areas where the information we have about certain factors is sparse and speculative, and even debated among biologists. Yet it shows how these factors don’t affect the Theory of Natural Selection in any way – details about how a result is reached do not mean that the result is not plainly visible. Coyne is exceptionally fair, and shows that the scientific process is careful to avoid assumptions, instead making inferences of what might be expected, then testing them to see if they hold up. He never asks the reader to take his word, but provides plenty of endnotes referring to specific studies on what he presents. While natural speciation takes far longer than we have been observing, we can see every factor required for it to take place, and have reproduced most of them in labs. We also have the distinct fossil evidence that upholds the suppositions without any contradiction, and experiments that show how the processes result in benefit to species. Through breeding programs, we knew long before Darwin came along that species are changeable – Darwin simple showed that it takes place on its own, and we’ve been finding further evidence for this ever since. Throughout it all, without engaging in digs or insults, Coyne shows how creationism provides no explanation whatsoever for most of the factors that biologists deal with routinely. Essentially, all of the evidence points to natural selection, repeatedly and testably, and nothing else has come close to explaining why we see all of the facts that we do. Indeed, the traits of countless species show that “design” isn’t really a word that can sanely apply, any more than most rivers can be said to travel “directly” to the sea. The fascinating part of evolution is how, through very simple environmental influences, species can nonetheless achieve a high degree of specific functionality. It’s slow, it’s haphazard, and it can result in complete dead-ends, but it still accomplishes a stunning amount.
Coyne saves the most contentious for last, dealing with human evolution in the final chapters. Scientifically, this isn’t contentious at all – such things come only from selfish emotions. We have a hard time simply accepting plain facts about ourselves when it comes to trashing some cherished belief, which is pathetic for a species claiming such high ground, really. Yet the evidence for human evolution is not lacking any more than the others. Coyne, again, is careful to state things very honestly, showing that the oft-quoted genetic similarity to chimpanzees of 98.5% doesn’t mean what we may think; genes produce proteins during fetal development, and such proteins shape the way we develop. Like a road map, one small turn can deviate from a path significantly. He also points out that the fossil record of hominids, our various ancestral species that split from chimpanzees roughly seven million years ago, does not present a distinct line. Fossil records are dots in history, and indicate an unknown number of branches and subspecies – indeed, we should not expect to find a nice progressive lineage, due to the specific conditions needed for fossilization and the low likelihood of the resulting fossils surviving intact to present day. There is no “line” running from Australopithecus afarensis through Homo habilis to Homo sapiens, and we cannot be sure that this is direct ancestry; but we can be sure that all are related, as they show development of distinct traits in stages leading up to modern humans, exactly as natural selection predicts. No other species possesses the traits that develop, nor do they fit the timeline. “Lucy” may be a distant grandmother or just an aunt, but is certainly one or the other.
I know from his website that Coyne isn’t terribly fond of evolutionary psychology, though he keeps this hidden when addressing it in the book. The reason for his skepticism, I believe, is that specific suppositions within are extremely untestable, and far too open to speculation without any ability to confirm. Evolutionary psychology postulates that much of our behavior stems from selected traits for survival in our ancestral species, which, overall, is a reasonable assumption and explains a lot about ourselves. As he puts it:
If we take the beginning of “civilization” at about 4000 BC, when there were complex societies both urban and agricultural, then only six thousand years have passed until now. This represents only one-thousandth of the total time that the human lineage has been isolated from that of chimpanzees. Like icing on a cake, roughly 250 generations of civilized society lie atop 300,000 generations during which we may have been hunter-gatherers living in small social groups.
Thus, we can fully expect to have some psychological or emotional traits induced by past pressures, which have not vanished under the extremely brief time that we’ve spent as we picture ourselves, the “rational human being.” I highlight this because it goes a long ways in explaining facets of our behavior, such as competitiveness and aggression, and can help us to understand that our motives may not solely be the rational thought processes that we believe. We know that various subconscious factors are at work in our psyche, we just cannot establish how and why they developed, buried as they are in non-fossilizing soft tissues of past brains.
Coyne presents a book for the public understanding of evolution, and takes pains to show not only that biologists (and the vast majority of other scientists) do not question it, but that we’ve established excellent reasons why not. Unlike the dogma it is often portrayed as, natural selection withstands every test we’ve thrown at it and grows stronger constantly with new information. I am not personally fond of using “truth” because it is a horribly abused word, but Coyne’s title is apt. Evolution is True, and it’s about time we accepted that and adapt to it.