Dr. Matthew Walker

And then all of a sudden, on the far right-hand side, you've got this one single data point that sticks out.

That's us, human beings.

And we don't fully understand why it is that we have such exceptional amounts of REM sleep.

Now, I've done a lot of hand waving and written some theories about why that is, but it's still very unclear.

The other thing, and that's a very, I can go very philosophical about the functions of REM sleep and how it changed as we made the transition as a species from tree to ground.

Because don't forget, as we mentioned in one of our episodes, when you're hanging like a bird on a tree or you're resting on a branch as a primate up in the trees,

and you go into REM sleep, you lose muscle tone.

So it's quite a fragile state when you're 30 foot up in the air and you've got gravity desperately wanting to bring you and your limbs down to the ground.

But when we made the transition down from tree to ground,

We no longer had to worry about that.

Did that open up the opportunity for more REM sleep to occur?

And that explains why we human beings have that.

We don't know.

REM sleep, however, does seem to be quite fundamental.

And fundamental from a life necessary perspective, there were some studies done back in the 1980s.

And there are studies that have not really been replicated.

And I think I agree as to why, because ethically, you know, they're right in that gray zone.

In fact, for me, I find them quite uncomfortable when I speak about them or even teach them in class.

They took rats and they deprived them of sleep, totally.

And what they found was that rats, on average, will die somewhere between about 13 to 17 days after total sleep deprivation.