©Copyright 2018 GEOSCIENCE RESEARCH INSTITUTE
11060 Campus Street • Loma Linda, California 92350 • 909-558-4548
Download PDF
This article was originally published as a chapter in the book “Design and Catastrophe: 51 Scientists Explore Evidence in Nature"
The extreme skull shape differences in the Canis familiaris (domestic dog; see Figure 28-1) have been postulated as an example of evolution since Darwin wrote On the Origin of Species.
Shapes and sizes range from the small, brachiocephalic (short-faced) Pekingese breed that can weigh as little as 2.5 kg to the larger dolicephalic (long-faced) Borzoi breed that can weigh up to 45+ kg, with multiple variations in between. These variations among the domestic dog are greater than the variation of skull shapes across the order Carnivora[1] and have been documented to occur in short time periods. For example, historical records of purebred St. Bernards were evaluated over 120 years and found to have undergone considerable morphological transformation.[2]
It has been suggested that the absence of survival pressures on dogs and their selective breeding and feeding have allowed all the different shapes to occur,[3] as some breeds would not survive without human protection/selection. Take for example the English Bulldog. Under most circumstances, the reproduction of the purebred English Bulldog is controlled by humans. The female is artificially inseminated because she cannot hold up the weight of the male during live breeding, and the pups are delivered by Cesarean section as the pelvic canal is too narrow for natural birth of the large-shouldered offspring.
The extreme changes in the bulldog result in brachiocephalic airway disease in which the soft palate is elongated and can drop into the upper larynx causing airway obstruction, with the nares having a decreased diameter resulting in reduced air flow and increased airway pressure. These changes in the airway result in numerous clinical problems including noisy breathing (stertor), exercise intolerance, heat intolerance, and difficult breathing (dyspnea). Associated with the brachiocephalic syndrome are other diseases such as fainting (syncope), gastrointestinal disease, increased prevalence of cancer, and obesity. These clinical diseases make it unlikely a bulldog could survive without human protection in the form of food provision (too aerobically challenged to chase down prey), protection from heat (most cannot tolerate temperatures above 30°C), and reproductive assistance. The selection of traits has resulted in reduced vigor and viability to the English Bulldog (the antithesis of evolution) but has not resulted in the bulldog becoming something other than a dog.
The evolutionary narrative purports that the plasticity of the dog skull is due to removal of the selective pressure of wild survival. But even in the absence of those constraints and in the presence of the most extreme breeding changes that can be implemented by humans, a domestic dog remains a dog.
Some see these observations on skull variability to uphold evolution, but I see them as examples of design. For example, a word processing program allows books, pamphlets, letters, and various other documents to be produced with very different formats and layouts; but no matter how much the settings are adjusted, a word processing program does not become a video game. The domestic dog (or potentially the entire Canis group) was designed in a similar fashion. Many different shapes and size potentials are in the system such that the skulls of various dogs may not even appear to be in the same order of animals and yet it remains Canis domesticus. The system was designed with such great variability that a domestic dog can be bred to have a long nose or a short one, upward or downward facing nose, a large or small head, long or short body and legs, or other variations. The original design is such that the domestic dog can assist humans in many capacities and forms, yet it is still a dog and by breeding cannot be made into another kind of animal.
The extreme changes in a domestic dog’s skull and overall conformation also give rise to another interesting thought relating to the fossil record. In many cases, we only have fossils to tell us of an extinct species or animal. No DNA or other data is available to make decisions about what species or group that fossil may fit into. If we did not already know the plasticity of a dog skull and found a fossil skull of both a Pekingese and a Borzoi, or a Chihuahua and a Greyhound, or any other very different dog breeds, we would be unlikely to consider the two fossils as individuals of the same species, or able to interbreed. This is an example of the limits of information that can be gathered from the fossil record.
Humans have pushed selection to the extreme in the various domestic dog breeds, yet they have been unable to create any species other than the domestic dog, an indication that different kinds of animals are not the result of evolution, but were created originally, as described in Genesis 1:24.
NOTES
[1] AG Drake, CP Klingenberg. Large-scale diversification of skull shape in domestic dogs: disparity and modularity. The American Naturalist 2010; 175(3):289–301. doi:10.1086/650372.
[2] AG Drake, CP Klingenberg. The pace of morphological change: historical transformation of skull shape in St Bernard dogs. Proceedings of the Royal Society B–Biological Sciences 2008; 275(1630):71–76.
[3] Drake and Klingbert 2010, op. cit.; FA Machado, TMG Zahn, G Marroig. Evolution of morphological integration in the skull of Carnivora (Mammalia): Changes in Canidae lead to increased evolutionary potential of facial traits. Evolution 2018; 72(7):1399–1419. doi:10.1111/ evo.13495.
Rebecca J. Greer is a criticalist at Veterinary Specialty Services in St. Louis, Missouri. She holds a DVM and MS from the University of Missouri, Columbia, and is a DAVCECC. In addition to performing attending and primary clinician duties, she trains residents and conducts occasional research projects with results published in peer-reviewed journals.