This was a claim by Lynn Margulis explained over at this link.
The sense organs of vertebrates have modified cilia: The rods and cone cells of the eye have cilia, and the balance organ in the inner ear is lined with sensory cilia. You tilt your head to one side and little calcium carbonate stones in your inner ear hit the cilia. This has been known since shortly after electron microscopy came in. Sensory cilia did not come from random mutations. They came by acquiring a whole genome of a symbiotic bacterium that could already sense light or motion. Specifically, I think it was a spirochete [a corkscrew-shaped bacterium] that became the cilium.
And why would our bodies incorporate spirochetes as part of our basic functionality?
There are many kinds of spirochetes, and if I’m right, some of them are ancestors to the cilia in our cells. Spirochete bacteria are already optimized for sensitivity to motion, light, and chemicals… If I’m right, the whole system—called the cytoskeletal system—came from the incorporation of ancestral spirochetes.