September 1, 2019 | Jerry Bergman

Snake “Vestigial Legs” Debunked

Do Evolutionists Do their Homework? Not in this Case.

by Jerry Bergman, PhD

I recently ran across a question from readers about why snakes lost their legs. The question was printed in a section of the BBC magazine titled Science Focus called Q&A which was answered by experts. In this case Rob Banino asked the question which was answered by Charlotte Corney, a zoo director and conservationist. The complete question and answer is printed below:

WHAT EVOLUTIONARY ADVANTAGE DID SNAKES GAIN BY LOSING THEIR LEGS?

It’s thought that snakes lost their legs 100 to 150 million years ago, but debate is still raging as to whether their limbed ancestors were aquatic or terrestrial.  The evolution of a long, legless body could be beneficial to life underwater as it would enable eel-like swimming.  But it could also be beneficial on land, making burrowing and hunting underground easier.  Either way, we can still see traces of their legs today:  boas and pythons, the most ancient surviving snakes, have tiny leg bones buried in the muscles towards their tail.  The more advanced snakes, however, have lost them completely.

Both the question and the answer assume Darwinism is true and are not only based on lack of evidence but are contrary to the evidence. The fact is, boas and pythons do not have vestigial legs but rather very functional mating spurs. In this case, the loss of legs story was begun by Darwin and repeated ever since, as if Darwin had the last word on the topic. Darwin concluded that snake spurs are “rudiments of the pelvis and hind limbs” and are evidence of the evolution of snakes from limbed ancestors.[1] Ever since then, Darwinists have used the fallacious argument that the support system for these claw-like, horny spur structures are vestigial “legs” left over from the snakes’ limbed past.

The Spurs’ Functions

These appendage claws, although small—particularly in the case of large constrictors—assist in locomotion. The claws are especially useful when climbing trees–their natural habitat–or when hanging from tree branches.[2] Over 150 years ago, the esteemed naturalist Edmond Gosse wrote that the “spurs” are unquestionably of use to the snake, such as to “help maintain a firm hold on a tree branch while watching for an approaching prey.”[3]

Evidence for the spurs’ usefulness includes the complex system used to attach them to the animal’s pelvis. Judging from the design of the bone and muscle structure, the claws appear to be well-designed, fully functional structures (see Figure 1). The bone and “calcified cartilage of variable shape and development … bears a cornified claw-like cap.”[4]

Their claws are moved by muscles anchored to bone, and the bone-muscle system allows the claws to function as strong grabbers.[5] They also “enable the snake to strike a powerful blow with its body,” strong enough to cut its victims when fighting in male territorial combat struggles. To effectively achieve this defensive task, the spurs have hard, black pigmented, horny caps attached to the bone support structure.[6] Conversely, they cannot be too large, otherwise they would interfere with the snake’s locomotion. Another function is the spurs are critical for courtship.

Use for Courtship

Males use their movable spurs to scratch or stroke the female during courtship and mating.[7]  Specifically, they are used by the “male to stimulate the female during copulation.”[8] The role of the spurs in courting and copulation for the anaconda snake were described in detail by herpetologist R. R. Mole as early as the 1920s.[9]

In another study, the male was observed persistently raking his spurs on the sides of the female’s body.[10] The spurs in females are much smaller, an indication that scratching is primarily a male courtship behavior. Yet another study observed that, during the courtship behavior of the Indian python, the

male would attempt to align his body with the female as she slowly crawled forward.  When the female would stop forward motion ….  and raise her head …  the male would initiate vigorous courtship [behavior].  The … male would loop his body over the female’s back and rapidly tongue flick the top of her head and back.  The cloacas would then be aligned, and the male would begin vibrating … against the female’s body in the region above her cloaca.  At this point the female would sometimes become receptive, arch her tail, gape her cloaca, and the male would insert one of his hemipenes.  During the 45-65 minute coitus, the male continued to stimulate the female with his spurs.[11]

Evidence that the claws of these snakes function for courtship includes the fact that the spurs protrude “only at the breeding season, functioning in courtship as does the similar spur of some male birds.”[12]

Other evidence for spur involvement in reproduction includes the observation that snakes with spurs lack erectile spines present in most other kinds of snakes.[13]  Snakes without spurs are forced to mate in very different ways than spurred snakes:

In many of the boas and pythons … courtship consists of the male using his claw-like [spurs] … to scratch or stroke his mate’s sides, but in [spurless] … snakes the male’s body is thrown into a rapid series of rippling waves which run forwards from tail to head.  ….  if she is physiologically ready for reproduction she responds by opening her cloaca and coitus follows.[14]

Fake News Evidence for Disputing Intelligent Design

The erroneous rudimentary leg claim is used as evidence against intelligent design. The argument usually is framed as follows: “Vestigial structures, such as the rudimentary pelvis of snakes and whales … are extremely puzzling if organisms are rationally designed” by an intelligent designer.[15] As noted, these structures are neither vestigial nor irrationally designed, but function extremely well for their intended purpose, as the reproductive success of snakes with them document. Another problem with the lost-legs claim is that tetrapods not only must have lost legs, but many other leg support structures including those shown in the diagram above. Plus, the neck, shoulders, and hindquarters would have changed drastically,

and the snake emerged as a long, symmetrical cylinder. It seemed to have become all tail, though actually it had shortened its tail, which was now merely a small appendage at the end of an amazingly long body. The body, indeed, seemed ludicrously long but the length was just another of those alterations that had to be made for the snake’s new method of locomotion.[16]

Another considerable change involves the ribs. Snakes would need to have evolved not only more ribs than tetrapods have, but very differently designed ribs compared to limbed animals. Along with the redesign, a very different muscle design would have been required. The “loss of a member in evolution is generally called a degenerate or ‘recessive’ step, yet most of the claimed improvements of the [leg-less] snakes came about by discarding” structures.[17]

If only people would do the research instead of repeating ad nauseum unfounded stories, like this one begun by Darwin, it wouldn’t be necessary to keep fact-checking bogus claims. Many of these stories become entrenched and get repeated only because they seem to support evolution. To show how easily just-so stories can be created, let’s revise Darwin’s story to tell it the opposite way: that the spurs are evidence of legless snakes evolving legs:

One excellent evidence of evolution is the evolution of legs in formerly legless animals, such as snakes. Snakes began evolving legs 100 to 150 million years ago, but the debate is still raging as to whether their non-limbed ancestors were aquatic or terrestrial. Nonetheless, we know the evolution of legs were very beneficial to life underwater as it would strongly facilitate not only more effective swimming due to their better control of movement in the water that limbs provide, but would also enable them to crawl around on the river bottom. Possibly, later on land, legs proved to be very beneficial, making travel faster, especially up hills, but also making burrowing and hunting far easier. They could also escape from predators far more effectively. It is obvious that all higher-level animals, reptiles, mammals and primates have all evolved legs for their many obvious evolutionary advantages. We can still see traces of the nascent evolution of legs today: boas and pythons—the most evolved snakes—have tiny legs in the muscles towards their tail. The less-advanced snakes, however, have not yet evolved them, but the survival advantaged legs confer makes it very likely that in 100 to 150 million years they too will have evolved functional legs.

This story sounds just as good as the other one. It is actually based on more fact than the original story told by Charlotte Corney, and the one told by Charles Darwin as well. Of course, nobody would be around to see if the prediction comes true.

References

[1] Darwin, Charles. 1859. The Origin of Species. London, UK: John Murray, p. 450.

[2] Dewar, Douglas. 1957. The Transformist Illusion. Murfreesboro, TN: Dehoff Publications, p. 169.

[3] Quoted in Murphy, John C. and Robert W. Henderson. 1997. Tales of Giant Snakes: A Historical Natural History of Anacondas and Pythons. Malabar, FL: Krieger Publishing, p. 101.

[4] List, James Carl. 1966. Comparative Osteology of the Snake Family Typhlopidae and Leptotyphlopidae. Champaign, IL: The University of Illinois Press, p. 44.

[5] Bergman, Jerry and G. F. Howe. 1990. Vestigial Organs are Fully Functional. St. Joseph, MO: Creation Society Books, p. 70.

[6] Storer, Tracy and Robert L. Usinger. 1977. Elements of Zoology. New York, NY: McGraw-Hill; Cardew, Gail and Jamie A. Goode (Editors). 2001. The Molecular Basis of Skeletogenesis. New York, NY: John Wiley and Sons.

[7] Shine, Richard. 1991. Australian Snakes: A Natural History. Ithaca, NY: Cornell University Press; Vences, Miguel and Frank Glaw. 2003. “Phylogeography, Systematics and Conservation Status of Boid Snakes from Madagascar (Sanzimia and Acrantophis).”  Salamandra, Rheinbach, 39(3-4):181-206; Murphy, John C. and Robert W. Henderson. 1997. Tales of Giant Snakes: A Historical Natural History of Anacondas and Pythons. Malabar, FL: Krieger Publishing; Carr, Archie. 1963. The Reptiles. New York, NY: Time Inc., p. 29.

[8] Griehl, Klaus. 1982. Snakes, Giant Snakes and Non-Venomous Snakes in the Terrarium. New York, NY: Barrons Educational Series, p. 11.

[9] Mole, R. R. 1924. “The Trinidad Snakes.” Proceedings of the Zoological Society of London, pp. 235-278, esp. pp. 237-238, March.

[10] Charles, Neil, Ray Field, and Richard Shine. 1985. “Notes on the Reproductive Biology of Australian Pythons, Genera Aspidites, Liasis and Morelia.” Herpetology Review, 16(2):45-48, p. 45.

[11] Murphy, James B., David G. Barker, and Bern W. Tryon. 1978. “Miscellaneous Notes on the Reproductive Biology of Reptiles. 2. Eleven Species of the Family Boidae, Genera Candoia, Corrallus, Epicrates and Python.”  Journal of Herpetology, 12(3):385-390.

[12] List, 1966, Ref. 4, p. 44.

[13]Boulenger, G. A. 2000. The Snakes of Europe.  Landisville, PA: Arment Biological Press.

[14] Parker, H.W. and A. G. C. Grandison. 1977. Snakes: A Natural History. Second Edition.  Ithaca, NY: Cornell University Press, p. 51.

[15] Barton, Nicholas H., Derek E.G. Briggs, Jonathan A. Eisen, David B. Goldstein, and Nipam H. Patel. 2007. Evolution. Cold Spring Harbor, NY: Cold Spring Harbor Laboratory Press, p. 75.

[16] Crompton, John. 1987. The Snake. New York, NY: Nick Lyons Books, p. 12.

[17] Crompton, 1987, Ref. 16, p. 12.


Dr. Jerry Bergman has taught biology, genetics, chemistry, biochemistry, anthropology, geology, and microbiology at several colleges and universities including for over 40 years at Bowling Green State University, Medical College of Ohio where he was a research associate in experimental pathology, and The University of Toledo. He is a graduate of the Medical College of Ohio, Wayne State University in Detroit, the University of Toledo, and Bowling Green State University. He has over 1,300 publications in 12 languages and 40 books and monographs. His books and textbooks that include chapters that he authored, are in over 1,500 college libraries in 27 countries. So far over 80,000 copies of the 40 books and monographs that he has authored or co-authored are in print. For more articles by Dr Bergman, see his Author Profile.

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