Nathan Lents is professor of biology at John Jay College of Criminal Justice in New York. In 2015, Dr. Lents wrote on his “Human Evolution” blog, “The human eye is a well-tread [sic] example of how evolution can produce a clunky design.” It’s clunky because
the photoreceptor cells of the retina appear to be placed backward, with the wiring facing the light and the photoreceptor facing inward…. This is not an optimal design for obvious reasons. The photons of light must travel around the bulk of the photoreceptor cell in order to hit the receiver tucked in the back. It’s as if you were speaking into the wrong end of a microphone.
According to Lents, “there are no working hypotheses about why the vertebrate retina is wired in backwards. It seems to have been a random development that then ‘stuck’ because a correction of that magnitude would be very difficult to pull off with random mutations” in the course of evolution.
In 2017, I published a book titled Zombie Science, which included a chapter on the human eye showing why the “clunky design” claim doesn’t fit the evidence. The claim is false because the photoreceptor cells in the human retina are so active that they must be nourished by a dense network of blood vessels and constantly renewed by a layer of specialized epithelial cells. If the blood vessels and epithelial cells were in front of the photoreceptor cells, where Lents thinks they should be, we would be almost blind. Instead, human eyes (and the eyes of other animals with backbones) are very well designed.
Apparently, Dr. Lents didn’t read my book. That’s OK; I don’t have time to read every book written even by my own colleagues. Instead, Dr. Lents just published his own book titled Human Errors, in which he repeats on page 5 his claim that the human eye is badly designed because the photoreceptor cells “appear to be installed backward.”
Over thirty years ago, Richard Dawkins had used this claim as an argument for Darwinian evolution in his 1986 book The Blind Watchmaker. Since then the argument has been repeated by evolutionary biologists George Williams, Kenneth R. Miller, Douglas Futuyma, and Jerry Coyne, among others.
But even before Dawkins published his claim in 1986, scientists writing in standard textbooks on eye physiology had shown why the “backwards retina” is functionally better than its opposite. Those scientists and textbooks included Gordon Walls in The Vertebrate Eye (Hafner, 1963); Sidney Futterman in Adler’s Physiology of the Eye (Mosby, 1975); and Paul Henkind, Richard Hansen, and Jeanne Szalay in Physiology of the Human Eye and the Visual System (Harper & Row, 1979). Abundant evidence that Dawkins’s claim was false had also been published in scientific journals in 1967, 1969, 1973, and 1985.
Obviously, Dawkins didn’t bother to check the scientific literature before claiming that the human eye is badly designed. He simply assumed that Darwinian evolution is true and that he knew how an eye should be designed. Williams, Miller, Futuyma, Coyne, and Lents also neglected to check the scientific literature when they repeated Dawkins’s false claim.
For most people (myself included), science is an enterprise that pursues truth by comparing hypotheses with evidence. For some people, science is an enterprise that searches for natural explanations on the assumption that everything can be explained in terms of material objects and the forces among them. Mind, spirit, free will, and God are excluded from consideration. The first is empirical science; the second is applied materialistic philosophy. When people persist in defending materialistic explanations even when they don’t fit the evidence (and are thus empirically dead), I call this enterprise “zombie science.”
The argument that the bad design of human eyes provides evidence for Darwinian evolution and against intelligent design is an example of zombie science.
Photo credit: analogicus, via Pixabay.