Recently, I watched a talk on the evolution of our eyes. Very early on, living things developed a single eye that was sensitive to just light and shadow. Life then developed a three-eye structure with 2 sensors on the sides and the original one up front.

In other words, most beings have 3 eyes, not 2. And yes, the third eye is actually the first.

Over time, the side eyes developed more. Different evolutionary tracks developed the eyes differently, like Octopi eyes have a different structure than those of invertebrates. But they follow the same principles: the ability to focus and a greater variety of receptors. For many animals, the side eyes moved forward for better depth perception. And the first eye moved back into the head. In humans, that eye is what we now call the pineal gland. It’s still light-sensitive.

Many reptiles still have the first eye on the surface. It looks like a forehead spot but remains light-sensitive.

In primates, however, its physical role is muted, but it continues to have a role in subtle perception. Particularly with its connection to the third eye chakra. 

Sight itself is powered by the third fire chakra in the gut. But in the multilayered nature of our existence, that first eye is tied to deeper seeing and knowing.
Davidya