Humans and octopuses both have camera-type eyes—a lens that focuses light onto a retina lined with photoreceptor cells. But despite the similar outcome, evolution took two completely different engineering routes. In humans (and all vertebrates), the retina is inverted: the photoreceptors face away from incoming light. Light must pass through layers of nerve fibers before reaching them. Those fibers then bundle together in front of the retina to form the optic nerve—punching a hole as they exit the eye. That hole is your blind spot, where no photoreceptors exist. Octopuses did it better. Their retinas are non-inverted—the photoreceptors face directly toward the light, and the nerve fibers connect behind the retina. No hole, no blind spot, and far less scattering of light. It’s a rare case where evolution solved the same problem twice—but one path (the vertebrate one) got stuck with a wiring error that natural selection couldn’t easily undo. The octopus eye shows what ours could have ...