Dr. Matthew Walker

But second, it's desaturated the blue light and it's the blue light, which is the lower wavelengths that are most deleterious to harming your melatonin. It's that black belt strategy. Blue light. By the way, do you know why it's the blue light that's so bad for your melatonin?

Why it's so powerful in terms of... Is that because when the sun is lowest in the sky in morning, it's... Oh, when the sun is highest in the sky, sorry, it's more blue. And when it's lower and it's going through more atmosphere, it's redder. Is that why?

Why it's so powerful in terms of... Is that because when the sun is lowest in the sky in morning, it's... Oh, when the sun is highest in the sky, sorry, it's more blue. And when it's lower and it's going through more atmosphere, it's redder. Is that why?

Why it's so powerful in terms of... Is that because when the sun is lowest in the sky in morning, it's... Oh, when the sun is highest in the sky, sorry, it's more blue. And when it's lower and it's going through more atmosphere, it's redder. Is that why?

Some of that is true, but it's not the main reason. It's because where we evolved from, evolved from the ocean, from the sea. And there, because of the way that light is refracted through water, the principal color of the sea, of the ocean, are blues. And so where we evolved our circadian rhythm originally was under the water.

Some of that is true, but it's not the main reason. It's because where we evolved from, evolved from the ocean, from the sea. And there, because of the way that light is refracted through water, the principal color of the sea, of the ocean, are blues. And so where we evolved our circadian rhythm originally was under the water.

Some of that is true, but it's not the main reason. It's because where we evolved from, evolved from the ocean, from the sea. And there, because of the way that light is refracted through water, the principal color of the sea, of the ocean, are blues. And so where we evolved our circadian rhythm originally was under the water.

And the way it was regulated was using light, but the color of light under the water was principally blue because it was kind of desaturated from the reds and the yellows. Isn't that amazing? That's so crazy. This isn't even reptile brain. This is fish. Oh, no. This is, you know, reptiles, amphibian, fish. We are way before, you know, avian and mammalian, you know, sort of emergence.

And the way it was regulated was using light, but the color of light under the water was principally blue because it was kind of desaturated from the reds and the yellows. Isn't that amazing? That's so crazy. This isn't even reptile brain. This is fish. Oh, no. This is, you know, reptiles, amphibian, fish. We are way before, you know, avian and mammalian, you know, sort of emergence.

And the way it was regulated was using light, but the color of light under the water was principally blue because it was kind of desaturated from the reds and the yellows. Isn't that amazing? That's so crazy. This isn't even reptile brain. This is fish. Oh, no. This is, you know, reptiles, amphibian, fish. We are way before, you know, avian and mammalian, you know, sort of emergence.

And by the way, it's only in birds and mammals that we see this thing called REM sleep or dream sleep. And it's a surprising thing. We still don't understand what that tells us about the functions of REM sleep. REM sleep is the principal stage in which we dream. And with every living species that we've studied to date sleeps.

And by the way, it's only in birds and mammals that we see this thing called REM sleep or dream sleep. And it's a surprising thing. We still don't understand what that tells us about the functions of REM sleep. REM sleep is the principal stage in which we dream. And with every living species that we've studied to date sleeps.

And by the way, it's only in birds and mammals that we see this thing called REM sleep or dream sleep. And it's a surprising thing. We still don't understand what that tells us about the functions of REM sleep. REM sleep is the principal stage in which we dream. And with every living species that we've studied to date sleeps.

What that means is that sleep probably evolved with life itself on this planet and fought its way through heroically every step along the evolutionary path. Ergo, if sleep doesn't serve an absolutely vital function, it's the biggest mistake the evolutionary process has ever made, and we now realize why it didn't make a blunder.

What that means is that sleep probably evolved with life itself on this planet and fought its way through heroically every step along the evolutionary path. Ergo, if sleep doesn't serve an absolutely vital function, it's the biggest mistake the evolutionary process has ever made, and we now realize why it didn't make a blunder.

What that means is that sleep probably evolved with life itself on this planet and fought its way through heroically every step along the evolutionary path. Ergo, if sleep doesn't serve an absolutely vital function, it's the biggest mistake the evolutionary process has ever made, and we now realize why it didn't make a blunder.

But what's interesting is that what first came into being was this thing called non-rapid eye movement sleep. And for millennia, there was no rapid eye movement sleep. There was no dream sleep. Something happened when we went from amphibians, reptiles, and fish up to birds and mammals. Now, birds and mammals evolved separately in two separate lineages from reptiles, amphibians, and fish.

But what's interesting is that what first came into being was this thing called non-rapid eye movement sleep. And for millennia, there was no rapid eye movement sleep. There was no dream sleep. Something happened when we went from amphibians, reptiles, and fish up to birds and mammals. Now, birds and mammals evolved separately in two separate lineages from reptiles, amphibians, and fish.

But what's interesting is that what first came into being was this thing called non-rapid eye movement sleep. And for millennia, there was no rapid eye movement sleep. There was no dream sleep. Something happened when we went from amphibians, reptiles, and fish up to birds and mammals. Now, birds and mammals evolved separately in two separate lineages from reptiles, amphibians, and fish.

Birds have REM sleep, mammals have REM sleep. What that means, firstly, is that REM sleep evolved twice independently in the course of evolution. When you see the same thing evolve twice or more times, like eyes, for example, it tells you that it's probably a fundamental trait of a living species.