A new theoretical synthesis suggests that vertebrate eyes, including human eyes, may not have evolved directly from the paired eyes of early bilaterian animals. Instead, researchers from the University of Sussex and Lund University propose that vertebrate eyes were "reinvented" from a single light-sensitive organ after its original paired eyes were lost. This theory is supported by the fundamental differences in photoreceptor types: vertebrate eyes utilize ciliary photoreceptor cells (rods and cones) for image-forming vision, a characteristic distinct from most invertebrates like arthropods and cephalopods, which primarily rely on rhabdomeric photoreceptor cells. The vertebrate retina uniquely integrates both ciliary and rhabdomeric components, with ciliary cells handling vision and rhabdomeric cells monitoring ambient light and relaying information.