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Trilobites of the genus Phacops have a large number of lenses. Rather than being hexagonal, the shape of these lenses is more reminiscent of a marble’s. If you gaze through a clear marble, you perceive an indistinct image that is reversed and blurred, showing objects to the sides elongated out of proportion. The reason for this is that light passing through a spherical structure is refracted at different angles. Therefore, it can be assumed that the problem of lack of focus in the marble should also be expected to arise in Phacops’s eye. But such is not the case!
In 1972, Kenneth M. Towe of Washington’s Smithsonian Institution showed just how efficient the Phacops eye actually was. Towe managed to obtain an image from inside the trilobite’s lenses and reflect it onto photographic paper. Contrary to his expectations, he encountered an exceedingly sharp image. It was as if the laws of physics no longer applied here.
The truth was only realized several years later. The trilobite eye did not actually ignore the laws of physics at all. On the contrary, it overcame any indistinctness thanks to a plan based on those same laws. Riccardo Levi-Setti solved the mystery of how this happened.
The trilobite was an ideal subject of research for Levi-Setti, a professor of physics at Chicago University and also a fossil hunter. He was familiar with fossil trilobites and, using his knowledge of physics, he made a most interesting scientific discovery. The trilobite lens had a similar structure to the optical constructions worked out by Descartes and Huygens in the 17th century.114 Levi-Setti published his findings together with his paleontologist colleague Euan Clarkson from Edinburgh University. In later years, he turned his research into trilobites into a book.
René Descartes was a French philosopher and mathematician. Christiaan Huygens was a Dutch astronomer and physicist. Both carried out physical and mathematical investigations into the refraction of light, and investigated the ideal shape of telescope lenses. Thanks to two mathematical functions with four variables that each discovered independently of the other, they played a major role in the development of better telescopes, and thus advanced the science of optics. However, they were quite unaware that they were using lenses based on the same mathematical principle that trilobites had been employing, millions of years before the science of optics was ever dreamed of.
Niles Eldredge, a prominent evolutionist and curator of the Department of Invertebrates, American Museum of Natural History, summarized this astonishing state of affairs:
These lenses—technically termed aspherical, aplanatic lenses—optimize both light collecting and image formation better than any lens ever conceived. We can be justifiably amazed that these trilobites, very early in the history of life on Earth, hit upon the best possible lens design that optical physics has ever been able to formulate.115
Richard Fortey, a researcher at the Natural History Museum in London and a professor of palaeobiology at Oxford University, said this about the trilobite genus Fallotaspis:
We know that the first trilobites already had a well-developed visual system. Indeed, the large eyes found in the genus Fallotaspis, from Morocco, prove that sophisticated vision goes back at least 540 million years to the Cambrian period.116