[MUSIC] [BIRD CHIRP] Your eyes are beautiful. They’re amazing bits of biological engineering. Just like a camera, remove one of their intricate parts, and the eye can’t do its job. For this reason, many people think eyes couldn’t
possibly arise from a blind process like natural selection. But that idea doesn’t hold vitreous
fluid. Light-sensitive cells first showed up in simple
single-celled creatures, helping them swim towards the sun.
Cup-shaped light spots then began to let creatures sense light’s direction.
Deeper pits eventually formed a pinhole iris, increasing the eye’s resolution.
Some animals developed a protective, crystalline covering over the iris, which later allowed
them to focus and control the light entering their eye.
This is essentially the eye we have today. Computer simulations have replayed this selective
process in just 350,000 generations, showing simple light patches can evolve into camera-like
eyes in tiny, adaptive steps, 1,829 to be precise. Nature took a little longer than that, but genes, biochemistry, fossils, and anatomy
all tell the same story. Eyes are pretty easy to evolve. So easy that nature has done it
independently 50 to 100 times. This kind of complexity, rather than overthrowing
Darwin’s theory, is proof of its power. So whether it’s an eagle observing ants
from atop a skyscraper, a mantis shrimp scanning circularly polarized light, or you watching
YouTube videos, there’s room for an eye in evolution. Stay Curious.