One of the most common arguments proponents of Creationism and Intelligent Design like to put forth as a flaw in Evolutionary theory is the supposed irreducible complexity of the human eye. The basic argument being that something as complex as the human eye couldn’t possibly have evolved by random chance so it must be the result of intentional design. Even Darwin found the idea of the eye being the result of evolution a difficult idea to swallow and it’s been a favorite target of his critics for decades. Now a German research team at the European Molecular Biology Laboratory are reporting that they have elucidated the evolutionary origin of the human eye in a paper published this week in the journal Science.
Researchers in the laboratories of Detlev Arendt and Jochen Wittbrodt have discovered that the lightsensitive cells of our eyes, the rods and cones, are of unexpected evolutionary origin—they come from an ancient population of light-sensitive cells that were initially located in the brain.
“It is not surprising that cells of human eyes come from the brain. We still have light-sensitive cells in our brains today which detect light and influence our daily rhythms of activity,” explains Wittbrodt. “Quite possibly, the human eye has originated from light-sensitive cells in the brain. Only later in evolution would such brain cells have relocated into an eye and gained the potential to confer vision.”
The scientists discovered that two types of lightsensitive cells existed in our early animal ancestors: rhabdomeric and ciliary. In most animals, rhabdomeric cells became part of the eyes, and ciliary cells remained embedded in the brain. But the evolution of the human eye is peculiar—it is the ciliary cells that were recruited for vision which eventually gave rise to the rods and cones of the retina.
If this holds up under peer review it’ll be a major step forward in our understanding of Evolution and a major setback for a lot of “God did it” proponents who hope to get their “alternative” theories taught in schools. At the very least it shows the human eye isn’t anything close to being irreducibly complex and that, unlike Intelligent Design, the theory of Evolution continues to, if you’ll pardon the pun, evolve over time.