The Evolution of the Human Eye, Complete With Its Inside-Out Retina
https://www.humantruth.info/evolution_of_the_human_eye.html
By Vexen Crabtree 2025
The human eye is a prime example of the blind and unintelligent nature of evolution. As species branched and evolved from one-another, the eye has undergone many changes. Solutions that are selected for in one species sometimes, by pure chance, never occur in another species. The Human eye sees fewer colours than some other species1, doesn't capture quite as much field of vision as many, is less accurate than some, and suffers from problems such as a detached retina and isn't well-designed for close-range work with tools and devices; we develop short-sightedness, long-sightedness and colour-blindness as a result of genetic shortcomings built-in to the very design of life.
The evolution of the eye has been a key intellectual battleground between religious creationists and scientists2, which creationists (or 'intelligent design' proponents) lost. But we now know in detail across species, from how partial-vision evolved in fish into full-vision: what we don't know is why God would have designed the octopus with a sensible eye with its neurones outside of the eyeball, but in primates such as humans, foolishly put the neurones inside the eye-ball, creating the small blind-spot3. That was just poor engineering. Why don't eyes across species all have maximally functional and efficient designs? Because evolution is itself blind.
1. The Eye
The history of the eye has been carefully documented by evolutionists; from its basic form in ancient fish, to designs of ever-increasing complexity and functionality. The professor of evolutionary biology Massimo Piugliucci writes that "we now have both a set of computer simulations showing how the complex vertebrate eye can evolve from simple photoreceptors, and a collection of currently living organisms actually displaying many of the predicted forms (all perfectly functional, which answers the classic creationist question of 'what is half an eye good for?')"2.
The eye has developed independently in quite a few species in quite a few different ways. This why there is so much difference between the eyes of species. It is possible to take eye-forms and map them; we find that their forms are similar in species that evolved from common ancestors. This is why all vertebrates have the same style inside-out retina.
Despite the facts, there are still many religionists who believe that the human eye is not evidence for the blind nature of evolution. Instead, they believe it is evidence for intelligent design (creationism) and declare that the human eye displays a feature called "irreducible complexity". This means that it cannot have evolved from its simpler forms because "what good is half an eye". Although this arguments stems from William Paley (early 19th century) many such people remain unaware, or choose to ignore, the multiple simpler forms of the eye which exist in nature. The creationist view is espoused particularly by fundamentalist Christians from the USA.2
2. The Frequency Range of the Visible Spectrum 4
What we experience as 'visible light' is arbitrary, and different species have evolved to see various different combinations of frequencies of light. What we call 'infrared' and 'ultraviolet' and can detect with scientific instruments, other species can see with their natural eyes.
“
The unaided brain concludes that only visible light exists. Many kinds of animal know better. They live in a different visual world, oblivious to parts of the human visible spectrum, sensitive to some wavelengths outside it. Below 400 nanometers, butterflies find flowers and pinpoint pollen and nectar sources by the pattern of ultraviolet rays reflected off the petals. Where we see a plain yellow or white blossom, they see spots and concentric circles in light and dark. The patterns have evolved in plants to guide insect pollinators to the anthers and nectar pools. With the aid of appropriate instruments we can now view the world with butterfly eyes. [...]
[But] why can't our species, the supposed summum bonum of Creation, do as much as all the animals combined, and more? [...] Evolutionary biology offers a simple answer. Natural selection [...] prepares organisms only for necessities.”
"Consilience: The Unity of Knowledge"
E. O. Wilson (1998)1
3. The Retina
There was no foresight or plan in the development of the human eye, and our vertebrate ancestors evolved an unfortunate feature: an inside-out retina. The nerves that carry signals from the rods and cones in our retina lay on the sensors instead of under them. This is because once something starts evolving, there is no easy way to restart the design. Things move on, and new designs build on old ones.
As the eyes increased in resolution, more and more nerves lay on the inside of the retina; their way to the brain remains a hole in the retina which now features as the blind spot in our vision. A little foresight on the behalf of nature would have led to a much more sensible design! The biologist and philosopher Daniel C. Dennett comments, "no intelligent designer would put such a clumsy arrangement in a camcorder, and this is just one of hundreds of accidents frozen in evolutionary history that confirm the mindlessness of the historical process"5. It is one the many daft features of our bodies which made anthropologist Scott Atran come to call the whole spectacle "unintelligent design" and declare that there is no God running the show - "why did he invert the retina and give humans (but not the octopus) a blind spot?" he asks6.
“Other animals, such as octopodes and squids, have their eyes wired more rationally. [...] The retina of the eye evolved as a modification of the outer layer of the brain that gradually developed light sensitivity. The eye is neither poorly nor well designed. It is simply not designed. Eyes provide such obvious survival value that they developed at least forty times independently in the course of evolution.”
"God, the Failed Hypothesis: How Science Shows That God Does Not Exist"
Prof. Victor J. Stenger (2007)3