New Model Traces Human Retina to 600-Million-Year-Old Single Eye

3 articles · Updated · ScienceAlert · Aug 1

A Current Biology model argues vertebrates’ paired retinas evolved from a single median eye in a worm-like marine ancestor that lived about 600 million years ago.
Comparisons across living animals suggest evolution reused that central light-sensing organ’s cells and neural circuits when descendants became active swimmers and needed more sophisticated vision again.
The proposal also links the same ancestral organ to the pineal and parapineal systems, offering a shared origin for vision-related circuitry and light-linked sleep regulation.
Retinal complexity may fit that scenario because rods and cones come from one photoreceptor lineage, while ganglion and other processing cells trace to another that the ancestral organ may already have combined.
No fossil of the one-eyed ancestor has been found, so the study is an evolutionary reconstruction, though a 2024 lamprey study supports the idea that key retinal cell types arose early in vertebrate history.