Rhodopsin is similar in both structure and absorption characteristics to the cone pigments most sensitive to wavelengths in the middle of the visual spectrum, and it evolved from those pigments hundreds of millions of years ago.

• 就构造与吸收光谱特性而言，视紫质与中波长锥色素最为相似；几亿年前，视紫质从这些中波长锥色素演化了出来。