Introduction
Some advocates of young earth creationism* have claimed that the nautilus functions identically to a submarine, by changing the gas pressure within its internal sealed chambers. While “evolutionists” believe that they evolved from mollusks that grew extra sections of shell as a flotation device, the fossil record shows that the nautilus has always looked like today's nautilus, without any intermediate evolutionary change. No one would believe a submarine happened by accident, they say. So why believe that "nature's submarine" occurred by accident?
Analysis
It is no surprise to evolutionary biologists that the phragmocone (shell chambers) is the main evidence left over in the evolution of the nautilus, as the only part of these creatures that can be easily preserved is the shell. (1) Additionally, while very little change has occurred on the nautilus body plan for the last several million years, this is again not very surprising, due to the evolutionary success of the body plan in question. Many plants and animals that are incredibly well adapted to their environments experience very little evolutionary change over time due to their already being so well suited for that environment. (2) In regards to the nautilus specifically, the sub-order Nautilina can be traced directly back to the Triassic, and has remained almost totally unchanged since then. (3) This does not imply the organisms in question did not arise through natural selection, nor does it mean that we are unable to trace that evolutionary path through the fossil record despite the claims made by the authors of Have You Considered? This path is observable directly based on the remains left behind by these creatures and their ancestors. Limpet-like creatures (4) are the most likely candidate for the direct ancestors of our modern nautilus, due to the similarity in shell formation found in the two. (5) The next step came with the evolution of elongated shells as is observed in Orthoceras. (6) This wasn't an ideal step, however, as, while it increased mobility, it made it more likely that the shell would be abused/damaged by the environment (5), and as such, the shell began to curve. (7) The clear result of this shell curving would culminate in the hyper-abundant ammonites, whose earliest representatives (8) had buoyant chambers that were incredibly similar to their Orthoceras ancestors (while not directly related, this is clear evidence of common descent). (5) Ammonites would eventually go extinct after having reigned for millions of years, though the effective nature of their body plan would eventually be refined over the years until the arising of the modern nautilus. (5) (7b)
Conclusion
In closing, the evolution of the modern nautilus can be traced clearly within the fossil record, a fact which cannot be said about submarines.
Bibliography
* Vonvett, J., Malone, B. (2017) Have You Considered? Evidence Beyond a Reasonable Doubt. (1st ed.). Search for Truth Pub.
1. Wikipedia. (2015, October 19) Phragmocone. LINK.
2. Wikipedia. (2021, May 27) Living fossil. LINK.
3. Wikipedia. (2021, April 13) Nautilina. LINK.
4. Wikipedia. (2021, March 25) Limpet. LINK.
5. Washington State University Tri-Cities Natural History Museum. (2014) The Evolution of Cephalopod Molluscs. LINK.
6. Wikipedia. (2021, May 13) Orthoceras. LINK.
7. Wikipedia. (2021, April 16) Nautiloid (Fossil Record). LINK.
(This phenomenon of shell-curving can be noted clearly in the Ordovician nautiloid Trilacinoceras)
7b. Wikipedia. (2021, April 16) Nautiloid (Evolutionary history). LINK.
8. Wikipedia. (2021, April 28) Goniatite. LINK.
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