> But the red light from fires would often be present when our ancestors were sleeping. I don't believe this is related. I believe it's simply that blue is the

> But the red light from fires would often be present when our ancestors were sleeping. I don't believe this is related. I believe it's simply that blue is the best/easiest/earliest color. The circadian rhythm is ancient, used by bacteria, plants, and mammals [1], long before humans had fire. Blue is most energetic, and is all that can be seen in the depths of the ocean, where life mostly likely originated. [1] https://schaechter.asmblog.org/schaechter/2023/04/sensing-blue-light-from-bacteria-to-birds.html https://schaechter.asmblog.org/schaechter/2023/04/sensing-bl...