The Zoology graduate students recently challenged misconceptions about evolution published in a letter to the editor of the O'Colly. The full response is reprinted below.

Evolution: An understanding, not a belief

The Zoology Graduate Student Society has chosen, as part of our mission as science educators, to clarify a number of inaccuracies found in the October 24th opinion article titled “Evolution arguments refuted”. Our society disagrees with the manner that biological evolution by natural selection, and related topics within paleontology and geology, have been presented in ways ranging from disingenuous to blatantly false. In order to clarify potential confusion created by these statements, we present here a full rebuttal of arguments presented by Mr. Patterson in his opinion piece.

Evolution is not an origin of life theory; it is a theory that addresses how life has changed over time, how it diversifies and adapts to the Earth's ever-changing conditions. The reason that evolution has a voice in science, while creation arguments do not, is because evolution is science. Science relies on the testing of questions and hypotheses to better understand the underlying patterns and mechanisms of our world and universe. Creation starts with an explanation and applies it to any encountered question. This is the key difference, and the reason creation is not in any way, shape, or form a science: it applies an answer to questions, instead of asking questions to find answers. You can argue about fairness, debates, or however you wish to frame it; the fact remains that creation isn’t science.

Evolution and Complexity

Increasing complexity of organisms is documented in the evolutionary record. It is not however a rule to which all evolution adheres. Reduction and loss of structures is common and observable in modern organisms, such as lost or reduced eyes in cave dwelling or subterranean organisms (Protas et al. 2007; Protas et al. 2011). Loss of digits in the evolutionary history of horses (decreasing complexity) (MacFadden 1992), or the addition and restructuring of hand and foot bones in the earliest amphibian ancestors’ limbs (increasing complexity) (Ahlberg and Clack 2006; Shubin et al. 2006)) bolster this statement. These examples are widely known among biologists and paleontologists, and are in no way the controversial evidence Mr. Patterson frames them as. Evolution can drive organisms to complexity or simplicity in response to selective pressures. In either case, evolution is still happening.

Sedimentology and the Rock Record

Sedimentology and its related topics within geology are hardly the “black box” Mr. Patterson claims. In fact, observations of these natural processes, along with the fossil record, represent the foundations of the science of geology; they have been painstakingly worked out over centuries of natural science. The accumulation of both inorganic and organic material (sediment) over vast amounts of time through processes of deposition results in rock layers or strata (Boggs 2011). The natural forces that cause the transportation and deposition of this sediment (wind and water primarily) can also commonly remove deposited materials from where they were previously laid down (James and Dalrymple 2010). Consider that wind can deposit dust on your car, but can also blow it away; water can move dirt or sand from one place to another, only to pick it up and deposit it elsewhere later. In fact, the erosion of previously deposited materials is common on Earth today, as well as in the geological record. When some previously deposited materials are eroded away and then more material is deposited, the result is a “break” in the sedimentary record and is called a disconformity. The phenomenon that Mr. Patterson finds so distressing is one of the fundamental observations that allows scientists to understand the history of Earth (Hutton 1795; Krauss 1999).

God of the Gaps, and the Flaws of the Missing Links Argument

A god-of-the-gaps argument against the completeness of the fossil record creates an ever-narrowing space with which to claim ignorance, or lack of evidence. Consider that in Darwin’s time detractors claimed the fossil record lacked “missing links” to explain the origins of birds through evolution. Today we know of Archeopteryx, Caudipteryx, Microraptor, Confuciusornis, and many other gorgeously complete fossils that draw a strong line connecting dinosaurs to modern birds (Hou et al. 1995; Owen 1863; Qiang et al. 1998; Xu 2006; Xu et al. 2000; Zhou 2004). Further, detractors of evolution have asked where the missing links between fish and amphibians are, to explain early terrestrial tetrapods, or a highly primate-like hominid linking Homo sapiens with the great apes. Tiktaalic roseae and Ardipithicus ramidus, respectively, provide exquisite evidence of intermediate evolutionary stages (Ahlberg and Clack 2006; Lovejoy et al. 2009; Shubin et al. 2006; Suwa et al. 2009; White et al. 2009)! Yet still, detractors cry out for further evidence, or belittle evidence once it has been wholly provided as inadequate. This speaks to a need to undermine undeniable advancements in understanding that conflict with an ideology-based approach.

The evidence in favor of evolution through time is crushing (Binida-Emonds 2007; Macfadden 1992; Norell and Xu 2005; Wang et al. 2010). Drawing from vertebrate natural history alone, we find vast evidence for modified forms and radiations of organisms through time (Grant and Grant 2006; White et al. 2009; Xu 2006; Zhou 2004). Dinosaurs and birds, the evolution of dogs, horses, whales, and humans, the origin of tetrapods and the earliest amphibians from lobe-finned fish (Lovejoy et al. 2009; MacFadden 1992; Suwa et al. 2009; Wang et al. 2010; White et al. 2009). These are not mere fantasies of a conspiring scientific community. What's more, many of the discoveries in the fossil record have been confirmed by DNA-based studies of relations between organisms (Binida-Emonds 2007; Vargas and Fallon 2005).

Walking Whales and Human Tails

Mr. Patterson’s claim that whale legs are a myth is utterly false. Evidence from studies of whale and dolphin fetuses (Cooper 2009) and modern vestigial structures (Abel 1907) provide evidence easily visible to the naked eye in living forms. These vestigial structures were originally extensively documented in the early 1900’s by Dr. Othenio Abel, an Austrian paleontologist, via dissections (Abel 1907). Evidence of whale ancestry from the fossil record, which is backed up by genetic studies of whale evolution (Graur and Higgins 1994; Zhou et al. 2011), also confirms the ancestry of whales from four-limbed terrestrial mammals.

Studies of whale and dolphin fetuses show remnants of the pelvis, which would have provided structural support for the hindlimb in earlier evolutionary forms (Cooper 2009). On page 103, figure 20 of Cooper (2009), the image requested by Mr. Patterson is provided in gorgeous, clear color. Reduced pelvic and femur bones have been found in adult living whales (Abel 1907), including bowhead whales and fin whales, among many others. These pelvic and limb bone structures become more robust and recognizable as one moves backward through the whale fossil record (Madar 2002; Thewissen et al. 2001; Uhen 2004). From Rodhocetus and Ambulocetus to Basilosaurus and Dorudon, evidence for limb element reduction within the early whales is overwhelming (Gingerich et al. 1990; Gingerich et al. 1994; Thewissen et al. 2001; Uhen 2004). Fossil specimens of Ambulocetus and Rodhocetus have both been found with discernible, functional arms and legs (Gingerich et al. 1994; Madar 2002). Pakicetus, older than Rodhocetus and Ambulocetus, also has all four limbs in a state that implies it lived primarily on land (Gingerich et al. 1994; Madar 2002; Thewissen et al. 2001). Pakicetus’ status as a whale ancestor is based on similarities in the ear bones and skull (Thewissen et al. 2001). The post-cranial anatomy of Durodon is consistent with other whale ancestors, and is visibly akin to Rodhocetus and Basilosaurus in dental and cranial features (Gingerich et al. 1990; Gingerich et al. 1994: Uhen 2004).

Limblessness in snakes documents how minor changes in gene expression can result in changes to the thorax/abdomen vertebral transition (Cohn and Tickle 1999). During development this transition point signals cells to begin forming a pelvic girdle (Cohn and Tickle 1999). When this signal is reduced or absent a girdle does not form, as expected in limbed reptiles such as lizards. Development is an intricate process of linked events. In order for digits to form correctly, limb buds must form (Cohn and Tickle 1999; Copp et al. 2003). In order for limb buds to form, a girdle must be formed. And in order for a girdle to form it must receive positional information based on the identity of vertebra (Cohn and Tickle 1999).  Therefore any minor change in these events can greatly alter the developmental process products later (Copp et al. 2003). Snakes have nearly uniform morphology along their vertebral column and therefore very little information is present to specify the formation of a girdle to support forelimb or hindlimb development (Cohn and Tickle 1999).

During human development we do not grow into our tails as Mr. Patterson asserts. Humans, and all primates, have five types of vertebrae: Cervical (neck), thoracic (upper back, connect to ribs), lumbar (lower back), sacral (sacrum, part of the pelvis), and coccygeal (Ankel-Simons 2007; Moore et al. 2006). This last section, the coccygeal vertebrae, make up the tail, and are numerous and functional in many primates (Ankel-Simons 2007). In humans, the coccygeal vertebrae have been reduced in number, usually barely appearing in the human skeleton (Moore et al. 2006). Embryonic tissues that would produce coccygeal vertebrae are formed in human development, but before vertebra form a process called apoptosis occurs and several of those tissues disintegrate resulting in a reduction of coccygeal vertebrae (Kerr et al. 1972). Altering the early process greatly affects later developmental events (Copp et al. 2003). Any minor changes made during development can result in major morphological changes (Copp et al. 2003; Kerr et al. 1972). Therefore, while humans do not have functional tails as many primates do, the fact remains that we retain a few bones from the now drastically reduced structure. Again, this is a case of unused structures being reduced, a reduction in complexity over evolutionary time.

Viruses and Mutation

Mutations in DNA can form through errors in DNA replication, which is the process of copying genetic material inside of the cell (Pointer et al. 2012). These mutations can change what protein products a particular region of DNA codes for, as well as the magnitude of production (Fondon and Garner 2007; Pointer et al. 2012). Over evolutionary time, mutations that are beneficial, neutral, or harmful are generated. It is the beneficial mutations, built up and accentuated over time, that result in adaptive evolution through natural selection, modifying or forming new biological features. Mr. Patterson claims that mutations have never been shown to add information to the genetic structure of an organism. This claim is also patently false.Errors in crossing over during meiosis and errors in DNA replication can result in gene duplication, and repetitive DNA. This has been exceptionally well demonstrated in explaining differences in the skull and facial features of dogs(Fondon and Garner 2007; Pointer et al. 2012). Regarding viruses, predictive computer models of genetic evolution are critical in the application of flu vaccines every year (McHardy and Adams 2009).

Closing Thoughts

We hope that these examples have helped to clarify any confusion created by Mr. Patterson’s opinion piece. And no, the presence of this letter as an opinion article does not act to degrade its scientific value. What we have presented here are not opinions, nor are they statements made on faith in a dogmatic system, as some like to accuse. To the contrary, scientists live to prove each other wrong, to one-up one another with greater discoveries, and poke holes in each other’s arguments through novel studies and experiments. This rigor forms the backbone of the scientific endeavor. It forwards well supported ideas, and casts out that which has been exposed as flawed in the purpose it served or mechanism it explained. Principals of evolution by natural selection may seem, to some, a flawed concept at odds with science, or spirituality. It is in fact neither. As a science, evolution by natural selection is a concept that has withstood the test of time in explaining the remarkable variation of life on our wondrous planet. It makes no attempt to assign purpose to life, as a scientific concept, or uproot personal spirituality, no matter the perceptions of firebrands of any stripe. 

We close with a quote from Charles Darwin, and wish you all luck as the semester winds to a close. We’ll see you in class!

“There is grandeur in this view of life, with its several powers, having been originally breathed into a few forms or into one; and that, whilst this planet has gone cycling on according to the fixed law of gravity, from so simple a beginning endless forms most beautiful and most wonderful have been, and are being, evolved.”

- Charles Darwin

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