Why the norm of nature is 2 eyes?(except insects). Why not four, or just one?

Question

From whales to a frog the size of a fingernail, always two eyes.

In: 5

Answer 1

Evolution isn’t a process that produces “the best at xyz” rather it produces animals that are good at surviving in their environment; no more no less. Any extra adaptation without a major benefit would not survive. Extra eyes would require more brain to process. Extra brain would consume a ton of oxygen an energy. Two eyes allow for animals to have depth perception (ability to tell distance visually) where one would not allow that and more would consume energy without a true extra benefit.