Fish Scales and Body Armor Design

The U.S. Army is looking at fish for the future of body armor design. MIT investigators have uncovered some of the secrets of construction that enable fish scales to be lightweight, sturdy, flexible, and effective in repelling punctures.1

They used a variety of techniques to study the bony scales of the unique African freshwater Polypterus senegalus, which is reputed to have existed unchanged for 65 million years. It is a “living fossil,” with ancestors fossilized in cretaceous rocks.

Polypterus has diamond-shaped “ganoid” scales, each of which is comprised of a series of layers, like in a sandwich. The basement layer is a thin platy bone, and on top of that lies spongy bone, then cosmine (a hard mineral like dentine in teeth), and then shiny ganoin enamel that is secreted by the outer skin. The studies showed that not only does each layer offer a unique contribution to the overall strength of the scale, but that the layers are micro-stitched to one another to keep them from peeling apart.

Leo Smith of The Field Museum in Chicago, who was not involved in the research, said, “That doesn't surprise me that millions of years or hundreds of millions of years of evolution would be a good starting point for what we need for this day and age.”2 He referred to fish armor as having “been sort of fine-tuned during that time for different aspects.” But what evidence supports this assertion?

Ganoid scales appear in the fossil record suddenly and fully-formed, with no stepwise transitional scales either in the rock record or in living specimens. In addition, Polypterus senegalus surely should have evolved into something else by now, considering the fact that the extinct robust predators of its past—which presumably provided the necessary selective pressure to drive the evolution of these scales—have been missing for eons. Why does it still have its beefy armor, if there is no longer an evolutionary need for it? As a LiveScience report stated, “The armor may be overkill.”2

Honest researchers admit the dilemma: “Polypterus is an interesting relic….There is no satisfactory explanation for the survival to the present of certain fishes such as this one….”3 Rather than demonstrating evolution, Polypterus reflects the biblical reality that animals reproduce “after their kind,”4 and reveals ingenious design that must have required more than mutations over long periods of time for its construction.


  1. Bruet, B .J. F. et al. Materials design principles of ancient fish armour. Nature Materials. Published on July 27, 2008, accessed July 29, 2008.
  2. Bryner, J.Incredible Fish Armor Could Suit Soldiers. Posted on July 27, 2008, accessed July 29, 2008.
  3. Hickman, C. P. et al. 1997. Integrated Principles of Zoology, 10th ed. Dubuque, IA: Wm. C. Brown Publishers, 512-513.
  4. Genesis 1:21.

* Mr. Thomas is Science Writer.

Article posted on August 5, 2008.

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