December 9, 2019 | Jerry Bergman

Have Snakes Lost Their Legs?

 

Did scientists find a snake losing its legs, or did they find a new kind of animal?

by Jerry Bergman, PhD 

I responded to the issue of snake legs on September 1,[1] but the issue came up again as a result of a new fossil discovery. The most obvious concern related to the question of evolution is to keep in mind that loss of some structure—no matter what the structure—is not evolution. Darwin’s theory requires the gain of new structures, or modification of existing organs. Many paleontologists assume evolution when analyzing fossils, and thus interpret the evidence from a Darwinian worldview. For example, instead of letting the evidence speak for itself, the authors stated that these “new fossils help answer longstanding questions on the origins of snakes, such as how they lost their limbs and evolved their highly specialized skulls.”[2]

The authors of The Conversation article just quoted – Michael Caldwell, Professor of Vertebrate Paleontology at the University of Alberta, and Alessandro Palci, Research Associate in Evolutionary Biology at Flinders University – should have known better. A paper in Nature in 2006 by Apesteguía and Zaher made some of the same mistakes.[3] All four scientists need to take their evolutionary glasses off and explore other viable possibilities and interpretations for the fossil without jumping to conclusions.

Unasked Questions

One question the paleontologists should be asking is, in view of the number of examples they have found that appear to be similar, “Is this creature just another new reptile variety not related to snakes?”  From my reading of the literature in this area, this possibility has never been considered by the workers in the field. If I am wrong, I hope a reader can fill this gap in my knowledge!

Another question involves other body parts of these creatures. The reference above notes that the new find also requires not only evidence of the loss of four legs, but also evidence of how they “evolved their highly specialized skulls.” In other words, the skulls of the claimed snake finds were very different from modern snake skulls. And that’s not all that’s different in this fossil. The paleontologists should consider whether they are looking at a previously-unknown extinct animal that had legs, a snake-like body, and a very un-snake-like head, plus several other very un-snake-like traits. These animals have major anatomical differences from modern snakes and other reptiles. How did those evolve? The paper in Science Advances says,

their ancestral lizard-like skull condition include greatly increased gape size, increased skull kinesis, loss of temporal bones, and expansion of the attachment sites for the jaw adductor musculature. This highly modified skull creates difficulties in identifying homologies with other squamates, resulting in problems reconstructing phylogeny and in understanding the evolutionary acquisition and assembly of the snake skull and elongate body.[4]

Looking at the Evidence

The new fossil consists of what is described as a “beautifully preserved skull of an ancient snake with rear limbs.” Judging from the illustration in Science Advances, which described it as “largely uncrushed fossils,” I would describe them as crushed fossil fragments, although not as greatly damaged as other examples. They were embedded in rock that had to be carefully removed from the matrix and assembled. Fossils embedded in rock are virtually always distorted due to the temperature changes that cause expansion and contraction of the rock matrix, especially rock near the Earth’s surface. That is the case in most of the fossils described as precursors of modern snakes.

Although assigned to the genus Najash, the authors admit that this assignment is tentative:

The new specimens exhibit a similar overall morphology that permits their assignation to the genus Najash; however, pending a full taxonomic review and assessment of the morphological diversity and disparity, the snakes from the LBPA [La Buitrera Palaeontological Area] are here conservatively assigned to Najash.

The name assigned to the species is Najash rionegrina – a term after the Biblical snake with legs from Nahash (Hebrew for ‘snake’), and the Río Negro Province in Argentina, where the fossils were discovered.

The 2006 Nature article that analyzed another limbed-snake fossil, concluded that it

has commonly been thought that snakes underwent progressive loss of their limbs by gradual diminution of their use. However, recent developmental and paleontological discoveries suggest a more complex scenario of limb reduction, still poorly documented in the fossil record.[5]

True Confessions

Two points are worth noting about this new fossil. The first is that the find does not support the once-orthodox idea of gradual limb loss. To accept the evolutionary theory of snakes, they have to revise the “commonly thought” scenario of gradual limb loss, but exactly how they would revise it they don’t say. Notice how they admitted that evolution from a quadrupedal organism to one lacking legs is “still poorly documented in the fossil record.” The 2006 Nature paper stated the problem as follows: “understanding the earliest steps toward the acquisition of these remarkable adaptations is hampered by the very limited fossil record of early snakes.”[6]

Another area where the 2019 report contradicts the formerly orthodox view is, instead of a watery origin of snakes, this find supports the “hypothesis of a terrestrial rather than marine origin of snakes.”[7] The research on new find likewise concluded that Najash was a “terrestrial snake living in a desert, not an aquatic snake living in the ocean.”[8]

Another problem with the original 2006 paper echoed in the 2019 paper concerns preservation of the fossil. “Unfortunately, that first description of Najash relied on a very fragmentary skull. Scholars of snake evolution were left to guess at what the head of these ancient animals might have looked like.”[9] This contrasts with the 2006 find which was originally described as “an almost complete… 3D preserved snake skull.” But, as just quoted in 2019, it was actually “a very fragmentary skull.” These adjectives are obviously subjective, but they are closer to being almost arbitrary, due to the lack of any mathematical standard on which to base their subjective descriptions. Subjectivity is common when reading the paleontological literature. As one report admitted:

A long-standing hypothesis is that snakes evolved from a blind, burrowing lizard ancestor. A group of small, worm-like, small-mouthed burrowing snakes, known as scolecophidians have long been considered to be the most primitive living snakes.[10]

This certainly does not describe the 2019 find.

The Genesis Serpent

The genus name of the 2019 find, “Najash,” recalls the Biblical story of the Garden of Eden where sin entered into the world. Genesis suggests that “the serpent” lost its legs as punishment for deceiving the woman. It’s not clear this was a judgment on all snakes. it could be true but, if so, the only difference between the pre-Fall serpent and the post-Fall serpent would involve its legs. Before and after the curse, it was the same animal, with only one difference: namely, the lack of legs, requiring a different mode of locomotion. The reptiles described in these papers we’re considering, however, display many major differences between their putative ancestors, as well as between the fossils and modern snakes.

Summary

A theory of snake evolution requires the gain of—and major alteration of—numerous structures. Loss of legs is devolution, not evolution. This new fossil needs to be examined from the standpoint that it could be an extinct reptile not related to modern snakes. It is evidently not a transitional form between a non-snake and a modern snake.  The 2006 Nature report concluded that, according to their description of the find, the

new Najash specimens reveal a mosaic of primitive lizard-like features such as a large triradiate jugal and absence of the crista circumfenestralis, derived snake features such as the absence of the postorbital, as well as intermediate conditions such as a vertically oriented quadrate.[11]

Enough evidence exists in the reports of this find to question the evolutionary interpretation. The “snake-lost-its-legs” assumption comes from wearing evolution glasses that filter out other possibilities. A fresh look at the evidence is warranted, using the evidence alone. This fossil may represent some unique, but extinct, reptile – not a creature on its way to evolving into something else. There are plenty of extinct reptiles: pterosaurs, ichthyosaurs, and all the dinosaurs. Finding another one should not be surprising.

References

[1] Bergman, Jerry, 2019: “Snake ‘Vestigial Legs’ Debunked,” Creation-Evolution Headlines, September 1.
[2] Caldwell and Palci, 2019: “Extraordinary skull fossil reveals secrets of snake evolution.” The Conversation, November 20. [Emphasis added.]
[3]  Apesteguía, Sebastián and Hussam Zaher, 2006: “A Cretaceous terrestrial snake with robust hindlimbs and a sacrum,” Nature, 440: 1037-1040.
[4] Garberoglio, Fernando F.; et al., 2019: “New skulls and skeletons of the Cretaceous legged snake Najash, and the evolution of the modern snake body plan,” Science Advances, 5(11): 1-8,  November 20.
[5] Apesteguía and Zaher, 2006, Ref. 3, p. 1037.
[6] Ibid.
[7] Ibid.
[8] Caldwell, Michael and Alessandro Palci, 2019. “Beautifully Preserved Skull of ‘Biblical Snake’ with Hind Legs Discovered,” Live Science, December 6.
[9] Ibid.
[10] Ibid.
[11] Apesteguía and Zaher, 2006, Ref. 3, p. 1037. [Emphasis added.]


Dr. Jerry Bergman has taught biology, genetics, chemistry, biochemistry, anthropology, geology, and microbiology for over 40 years at several colleges and universities including 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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