Snake Legs, What Explains Them?

Certain members of the boa/python family, such as pythons and boas, still have remnants of their hind legs. These remnants, known as pelvic spurs, are the externally visible portion of the vestigial remnants of legs found on each side of the cloaca in primitive snakes. They are tiny leg bones buried in the muscles towards the tail, and are better developed in males, while very small or absent in females. These structures are considered vestigial and are evidence of the evolutionary history of snakes, suggesting that they descended from limbed ancestors[1][3][5]. The presence of these vestigial legs is not unique to pythons and boas, but they are the most well-known for this feature[5].

The term “vestigial” refers to a body part or organ that remains in a form that is small, imperfectly developed, and not able to function as it once did.

Creationists who deny the evidence of species evolution have argued that the presence of vestigial legs in some snakes does not support the theory of evolution. They believe that snakes may have had limbs before the Fall, as suggested in Genesis 3:14, where the snake is cursed to move on its belly. [6]

Evidence from the fossil record and from genetics supports the view that the complex systems we see around us are a result of billions of years of changes. This time span is nearly impossible to comprehend given that our entire lifetimes cover only several decades. Evolutionists who find the simple answers in Genesis lacking may suggest that creationists read The Blind Watchmaker by Richard Dawkins [13]. The controversy continues at the time of this writing, with approximately 62% of adults in the United States accepting human evolution, while 34% believe that humans have always existed in their present form [11].

The snake species Najash rionegrina, which lived around 90 million years ago, is known to have had hips and hind legs, providing evidence of its descent from a land-living lizard. This fossil discovery challenges the previous hypothesis that snakes came into existence as legless marine creatures. The presence of hips and hind legs in Najash rionegrina suggests that it led a burrowing lifestyle similar to modern burrowing snakes. The legs of this primitive snake were considered to be functional, indicating a transitional phase in the evolution of snakes from limbed ancestors[7][9].

Snakes do have neck vertebrae, although they are highly modified. The distinction between neck and trunk regions is unclear in snakes due to the complete absence of certain landmark structures. Snakes have a greatly increased number of vertebrae, with most of their skeleton being an extremely extended thorax. Ribs are found exclusively on the thoracic vertebrae, and the neck, lumbar, and pelvic vertebrae are very reduced in number. Some species, such as the boid family, can possess vestigial pelvic remnants. [10]

Development of limb buds begins in the 4th week of gestation. Squamate embryos have four limb buds at the phylotypic stage. The phylotypic stage is a developmental stage during which the basic body plan and major organ systems have formed. In squamates, which include lizards and snakes, this stage occurs approximately 22-24 days post-oviposition. At this stage, the limb buds become visible as small outgrowths on the sides of the embryo’s body, which eventually develop into the forelimbs and hindlimbs. While limb development starts in snake embryos, it is inhibited at an early stage, resulting in the absence or very reduced limb structures in adult snakes.

Citations:

^{[1] https://www.amnh.org/exhibitions/darwin/evolution-today/how-do-we-know-living-things-are-related/vestigial-organs
[2] https://crev.info/2019/09/snake-vestigial-legs/
[3] https://en.wikipedia.org/wiki/Pelvic_spur
[4] https://www.nature.com/articles/072630a0
[5] http://birds-to-dinosaur.blogspot.com/p/python-vestigial-pelvis-femur-and-spur.html?m=1
[6] https://reasons.org/explore/publications/articles/genetics-discovery-in-snakes-adds-legs-to-the-case-for-creation
[7] https://www.livescience.com/4090-millions-years-snakes-hip.html
[8] https://homework.study.com/explanation/do-snakes-have-hip-bones.html
[9] https://phys.org/news/2006-04-snake-hips-primitive.html
[10] https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3394116/
[11] https://en.wikipedia.org/wiki/Level_of_support_for_evolution
[12] https://www.pewresearch.org/religion/2013/12/30/publics-views-on-human-evolution/
[13] https://www.amazon.com/Blind-Watchmaker-Evidence-Evolution-Universe/dp/0393315703/}