Lizard Gives Clues On Evolution Of Eye

4/14/2006) Lizards have given Johns Hopkins researchers a tantalizing clue to the evolutionary origins of light-sensing cells in people and other species. The lizard study describes how the lizard's so-called third, or parietal, eye, distinguishes two different colors, blue and green, possibly to tell the time of day. Specialized nerve cells in that eye, which looks more like a spot on the lizard's forehead, use two types of molecular signals to sense light: those found only in simpler animals, like scallops, and those found only in more complex animals like humans. Although the blue-green color comparison method used by the parietal eye is not one shared by humans, it does reveal one potential step in the evolution of color vision, the Hopkins researchers say. The proponents of intelligent design assert that the combination of nerves, muscles, sensory cells, and lens tissue in the eye could only have been 'designed' from scratch but this new research gives new insight into the evolutionary development of light-sensing cells, key to the eventual development of eye-like structures and color vision.