Is the dog’s ‘collar bone’ vestigial?

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Published: 27 February 2014 (GMT+10)
dogs-running

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In comparison to human beings, dogs have a rather different shoulder design, and the same applies to many other carnivorous and hoofed animals too, such as and cats and horses. The shoulder bones appear somewhat disconnected from the rest of the skeleton and dogs don’t have the obvious collar bone (clavicle) that we humans have. The tiny canine clavicle has a variety of sizes and shapes in adult dogs1 and some evolutionists have argued that it is rudimentary; implying that it’s now a largely ‘useless leftover’ from an earlier stage in canine evolution. But claims of it being vestigial don’t stack up. Together with other parts of the shoulder anatomy (termed the ‘clavicular complex’), the clavicle plays an important role in canine locomotion.

Evolutionary claims

Arguments for vestiges invariably turn out to be arguments from ignorance or they reveal faith in evolution in the teeth of contrary evidence. Therefore, regarding the canine clavicle we must peel away the rhetoric to find out what is known about its function.

To pre-empt the accusation that creationists misunderstand or misrepresent the evolutionary argument about vestiges, we’ll first mention a recent promulgation of this argument by University of Chicago professor Jerry Coyne in his Why Evolution is True: “A trait can be vestigial and functional at the same time. It is not vestigial because it’s functionless, but because it no longer performs the function for which it evolved” (emphasis in original).2 However, this begs the question, for unless it can be empirically established that a trait is vestigial andshown to have once served a different role, the prior ‘function’ is just a statement of faith.

For 150 years ‘vestigial organ’ was defined in a manner similar to the following, from a popular 1998 biology text:

“Evolution is not a perfect process. As environmental changes select against certain structures, others are retained, sometimes persisting even if they are not used. A structure that seems to have no function in one species, yet is homologous to a functional organ in another species, is termed vestigial. Darwin compared vestigial organs to silent letters in a word—they are not pronounced, but they offer clues to the word’s origin.”3

Coyne’s revisionary definition indicates that he is aware that this traditional concept has proven to be indefensible. So his definition is self-serving, designed to make a failed concept seem to work again in the face of overwhelming evidence that truly vestigial organs (useless leftovers of evolutionary history) are very hard to find.4

Coyne does not engage at all with informed creationist writing on the subject and his ‘examples’ of vestiges are dealt with on this site (see the many articles linked here), for instance flightless birds, the eyes of cave-dwellers and whale ‘leg bones’ (here and here). His claim for the vestigial human appendix (now a tired old canard) illustrates that he is in denial (see here and here) and is merely keeping evolutionary faith: “…our appendix is simply the remnant of an organ that was critically important to our leaf-eating ancestors, but of no real value to us.”5 His discussion indicates that he is entirely ignorant of its long-known immune function and, on the contrary, the Appendix shrieks ‘Creation’. His other claims are also easily rebutted, the coccyx, erector pili muscles (that cause goose bumps) and the ability to wiggle your ears—see vestigial organs revisited.

With any alleged revisionist vestige, Coyne and his fellow evolutionists must first demonstrate (not merely assert) what function the body part had previously. And since that function presumably aided the ancestral creature’s survival (which is why the much-touted mutation and selection mechanism supposedly favoured its development in the first place), they must give substantive reasons why and how this function became unnecessary later on. Mere just-so stories are not science so they do not count as explanations. At the very least, one would expect to read a scenario about how a quite different body part evolved to gradually take over the vital function once performed by the now-vestigial body structure. Instead, Coyne’s own words give the game away: “But even after we’ve established that a trait is vestigial, the questions don’t end. In which ancestors was it functional? What was it used for? Why did it lose its function? Why is it still there instead of having disappeared completely?”2 This demonstrates the blatant contradiction in his own words, for, without knowing the answers to such questions, it cannot in any sense (scientifically or otherwise) be “established that the trait we see now is vestigial” by definition (emphasis added)!

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dog-leaping

The canine shoulder is a brilliant design

Arguments for vestiges invariably turn out to be arguments from ignorance or they reveal faith in evolution in the teeth of contrary evidence. Therefore, regarding the canine clavicle we must peel away the rhetoric to find out what is known about its function. Evolutionists often mistakenly assume that the relatively small size of a structure (or its absence) is proof of a loss of a former function. Nevertheless, in a paper devoted to this very bone and its related body parts the authors (both veterinary scientists and evolutionists) describe detailed and important functions.1 Their paper focuses on the clavicle of newborn puppies but is in agreement with the work of other veterinary scientists on adult dogs.6 During locomotion, the tiny clavicle and associated parts provide muscle stability and allow adjustment of the position of muscles involved in movements of the humerus (upper foreleg). The clavicle is important for the healthy articulation of the head of the humerus with the shoulder; without it, normal movement of the foreleg (towards the head or tail, or inwards, under the dog’s chest) could not occur. Furthermore, these functions of the ‘clavicular complex’ also protect blood vessels of the ‘armpit’ and the brachial plexus (a network of vascular tissue running from the neck into the leg) from mechanical damage during movement.

In other words, far from offering support for the evolutionary vestiges argument, detailed knowledge of the anatomy and function of the canine ‘clavicular complex’ points strongly to its economy of design. The construction of the dog’s ‘floating shoulder’ improves running efficiency, allowing a much greater stride length and higher running speed than would otherwise be possible. Of course, pet owners who have spent hours watching their dogs race around open spaces are very familiar with their impressive speed, agility and leaping ability—absolutely no evidence for inferior design here!

 

Related Articles

Further Reading

References

  1. Cerny H, and Cizinauskas S., The clavicle of newborn dogs, Acta Veterinaria Brno 64(2): 139–145, 1995. Return to text.
  2. Coyne, J.A., Why evolution is true, Oxford University Press, 2009, p. 62. Return to text.
  3. Lewis, R., Life, 3rd ed., WCB/McGraw Hill, New York, p. 395, 1998. Return to text.
  4. However, from a biblical view of history, it is reasonable to believe that organs may well have lost function due to natural changes since the Fall (e.g. blind cave-dwelling fish). Return to text.
  5. Ref. 2, p. 65. Return to text.
  6. McCarthy, P.H. and Wood, A. K., Anatomic and radiologic observations of the clavicle of adult dogs, Am. J. Vet. Res. 49:956–959, 1988.
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