Dr. Matthew Walker

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.

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.

So what we don't still understand though is why do birds and mammals require, why did REM sleep emerge into being? Now we've got some theories because one of the differences is that birds and mammals regulate their temperature. We are homeotherms. We get the ability to control our core body temperature. All of those other species don't.

So what we don't still understand though is why do birds and mammals require, why did REM sleep emerge into being? Now we've got some theories because one of the differences is that birds and mammals regulate their temperature. We are homeotherms. We get the ability to control our core body temperature. All of those other species don't.

So what we don't still understand though is why do birds and mammals require, why did REM sleep emerge into being? Now we've got some theories because one of the differences is that birds and mammals regulate their temperature. We are homeotherms. We get the ability to control our core body temperature. All of those other species don't.

So it has to be something to do perhaps with metabolic control to produce thermoregulation. There's probably other theories too, but nevertheless, going back to the evolutionary story and we'll come back to, I haven't forgotten the final T for QQRT, but I've put forward a theory that sleep actually never evolved. Why do we think that sleep evolved?

So it has to be something to do perhaps with metabolic control to produce thermoregulation. There's probably other theories too, but nevertheless, going back to the evolutionary story and we'll come back to, I haven't forgotten the final T for QQRT, but I've put forward a theory that sleep actually never evolved. Why do we think that sleep evolved?

So it has to be something to do perhaps with metabolic control to produce thermoregulation. There's probably other theories too, but nevertheless, going back to the evolutionary story and we'll come back to, I haven't forgotten the final T for QQRT, but I've put forward a theory that sleep actually never evolved. Why do we think that sleep evolved?

Why don't we think that sleep was the default state of all life and it was from sleep that wakefulness evolved? I've always been confused why we don't... Well, because you wouldn't be able to survive if you just slept, but you could survive if you just woke. The idea would be though, that if sleep is this initial default state, it is enough to support life and its existence.

Why don't we think that sleep was the default state of all life and it was from sleep that wakefulness evolved? I've always been confused why we don't... Well, because you wouldn't be able to survive if you just slept, but you could survive if you just woke. The idea would be though, that if sleep is this initial default state, it is enough to support life and its existence.

Why don't we think that sleep was the default state of all life and it was from sleep that wakefulness evolved? I've always been confused why we don't... Well, because you wouldn't be able to survive if you just slept, but you could survive if you just woke. The idea would be though, that if sleep is this initial default state, it is enough to support life and its existence.

And some of those species could reproduce potentially asexually. So you wouldn't have to necessarily be awake to find a mate. You could at least have a proto version of life. And the proto version requires this stasis state that we call sleep.

And some of those species could reproduce potentially asexually. So you wouldn't have to necessarily be awake to find a mate. You could at least have a proto version of life. And the proto version requires this stasis state that we call sleep.

And some of those species could reproduce potentially asexually. So you wouldn't have to necessarily be awake to find a mate. You could at least have a proto version of life. And the proto version requires this stasis state that we call sleep.

It would somehow accumulate nutrients by falling through gravity. Correct.

It would somehow accumulate nutrients by falling through gravity. Correct.

It would somehow accumulate nutrients by falling through gravity. Correct.

You know, think of, you know, there's any manner of static living organisms that stay in place that don't move around. But then at some point, there was enough evolutionary pressure to demand this thing called movement and demand higher levels of consciousness. And it was... So... That's one way of seeing it. I think the other is, let's say wakefulness came first.

You know, think of, you know, there's any manner of static living organisms that stay in place that don't move around. But then at some point, there was enough evolutionary pressure to demand this thing called movement and demand higher levels of consciousness. And it was... So... That's one way of seeing it. I think the other is, let's say wakefulness came first.

You know, think of, you know, there's any manner of static living organisms that stay in place that don't move around. But then at some point, there was enough evolutionary pressure to demand this thing called movement and demand higher levels of consciousness. And it was... So... That's one way of seeing it. I think the other is, let's say wakefulness came first.