Why Evolution Is True: Chapter-by-Chapter Analysis

What Is Evolution?

Jerry Coyne's Why Evolution Is True identifies six elements that together constitute the theory of evolution: (1) evolution itself; (2) gradualism; (3) speciation; (4) shared origins; (5) natural selection; and (6) nonselective evolutionary change mechanisms (Coyne, 2009). Of these, the most fundamental is the concept of evolution itself, which implies the genetic modification of any given species over time. Over many generations, species may transform into substantially different organisms because of DNA modifications that originate in the mutation process. Gradualism, the second element, describes how significant evolutionary transformations — such as the transition from reptiles to birds — unfold across many generations rather than all at once.

The subsequent elements can be considered two sides of the same coin. It is a remarkable fact that although innumerable living species exist, every one of them shares a small number of basic characteristics: the biochemical pathways used to generate energy, the standard four-letter DNA code, and the way that code is deciphered and converted into proteins within the body (Neuner, 2012). This observation is consistent with the view that all species can be traced back to a single common ancestor that possessed these characteristics, which were then inherited by its descendants. If evolution entailed only slow genetic transformation within a single lineage, the world would contain just one greatly evolved species. In reality, Earth harbors more than ten million living species and approximately 250,000 known fossil species. The diversity of life raises a vital question: how does such variety arise from a single ancestral form? The third evolutionary concept — speciation, or splitting — helps answer this question (Neuner, 2012).

Coyne's argument that evolution is a true occurrence is well supported. Every line of evidence gathered since Darwin's time points clearly to the fact that life on Earth evolves and that every species is related to every other. The belief that evolution has no basis or no impact on our species is difficult to sustain in light of this evidence. That said, it is important to distinguish between Darwinism and evolutionism more broadly. Jean-Baptiste Lamarck was himself an evolutionist who preceded Darwin, and Darwin was in turn influenced by Lamarck, particularly regarding the use and disuse of organs. Biologists are expressing increasing discontent with the traditional Darwinism that Coyne champions and that figures such as Pinker, Dawkins, and Dennett have popularized. Experts increasingly accept that a more pluralistic approach to evolution is needed, which explains the emergence of Third Way evolution (Vecchi, 2009).

Written in the Rocks: The Fossil Record

Professor Coyne provides a clear rationale for how the fossil record, despite being incomplete, strongly supports evolution and challenges creationism. Proponents of creationism typically invoke the argument of the missing link, asserting that the absence of transitional forms between major plant and animal groups undermines the evolutionary case. Coyne disagrees, noting that paleontologists are constantly discovering transitional fossils — including the much-publicized Ida, displayed to large crowds at New York's Natural History Museum. Such fossils give researchers a concrete picture of what assumed missing links may have looked like. Throughout this chapter, Coyne references numerous findings: fossils demonstrating that amphibians evolved from fish, and that birds evolved from reptiles, among others.

Coyne also refutes the longstanding argument that natural selection cannot account for biological innovations, since such an explanation would require proof of the adaptive benefit of every intermediate stage. He addresses the commonly cited example of wings: how would one percent, twenty percent, or fifty percent of a wing benefit any animal? Coyne offers a hypothetical but compelling scenario, supported by fossil evidence from China regarding the evolution of feathers and flight, which challenges the creationist case against Darwin's school of thought (Vecchi, 2009).

Fossil formation requires a highly specific set of circumstances: an organism's remains must reach a body of water, settle to its bottom, and be covered rapidly by sediment to prevent decay or scavenging. Given these conditions, one would naturally expect the fossil record to be incomplete. Estimates of the total number of plant and animal species that have ever inhabited the Earth range from seventeen million to four billion. Since paleontologists have uncovered approximately 250,000 distinct fossil species, the available fossil evidence represents only roughly 0.1–1% of all species that have ever lived — not a fully reliable sample of life's history. Nevertheless, the available fossil record is sufficient to give researchers a sound understanding of how the evolutionary process has unfolded and how major groups diverged from one another (Neuner, 2012).

Vestiges, Embryos, and Bad Design

This chapter demonstrates that several biological realities — atavisms (such as the vestigial tail in humans), cases of poor design (such as the gap between the Fallopian tube and the ovary), and organs with no apparent function (such as the appendix) — can only be satisfactorily explained by evolution. These features constitute unavoidable evidence of shared ancestry and reveal how the evolutionary process routinely modifies old genetic and phenotypic characteristics, adding or deleting features for diverse reasons, or for no adaptive reason at all (Vecchi, 2009).

According to Coyne, vestigial structures are characteristics that were functional in an organism's ancestors but have either lost their original utility or been repurposed — as in the case of the ostrich's wings. A structure is considered vestigial not because it has become entirely functionless, but because it no longer performs its original function (Coyne, 2009). The human appendix, for instance, is the remnant of a structure that was vital to humanity's herbivorous ancestors but serves little purpose today. "Bad design," as Coyne uses the term, refers to the observable flaws in organisms' bodies — flaws that an intelligent designer working from scratch would have had no reason to introduce. Because such flaws exist, they suggest evolution rather than intentional design (Neuner, 2012).

No biologist questions the significance of natural selection in biology — selection occurs constantly and unavoidably. A paradigm shift as radical as the one witnessed in physics at the end of the nineteenth century is unlikely to occur in evolutionary biology, since Darwinism is, in large measure, correct. The crucial point, however, is that natural selection does not operate in isolation, and it does not work precisely as neo-Darwinians have traditionally described (Vecchi, 2009).

References

Coyne, J. A. (2009). Why evolution is true. Penguin.

Neuner, K. (2012). Why Evolution Is True — Notes & Review. Retrieved November 22, 2016, from https://vialogue.wordpress.com/2012/05/06/why-evolution-is-true-notes-review/

Vecchi, D. (2009). Review — Why Evolution is True. Retrieved November 22, 2016, from http://metapsychology.mentalhelp.net/poc/view_doc.php?type=book&id=4953