The eye is an ingeniously designed biological mechanism. In 1802, William Paley used eyes as a clear illustration of what he called “contrivances,” i.e., “well-designed machines.” Before Charles Darwin’s publications, many naturalists used Paley’s textbook, Natural Theology.
Paley wrote regarding the eye’s adjustable lens: “Can anything be more decisive of contrivance than this? The most secret laws of optics must have been known to the author of a structure endowed with such a capacity of change.”1
He attributed the design and construction of eyes to the Creator God, whereas Darwin credited their design to nature. The retina contains tiny molecular machines that capture light and convert it into electrochemical signals. New research on how they do this emphasizes exactly why Paley was right.
Two molecules in the retina—vitamin A and a protein named “opsin” that together make “rhodopsin”—capture single light photons. When light strikes the vitamin, it changes shape and becomes the molecule “11-cis-retinal.” This in turn changes the rhodopsin’s shape. When light activates enough of these molecular switches within the light-sensitive cell, they cause downstream biochemical systems to amplify and send the signal from the retina, through the optic nerve, and to the brain. This complex photochemical reaction is at the heart of what allows eyes to detect light and send signals that the brain can form into meaningful images….
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