Note: this next bit of writing takes some artistic liberties when it comes to some to some of the science. This means there may be slight inaccuracies. Try to suspend disbelief for the moment and enjoy :)

From The Intergalactic Journal of Mechanics and Biology

The human cortical system is a marvel of biological engineering. It has multiple backup systems with feedforward and feedback processes. Damage the brain, and instead of death, you may simply damage only one area of functioning. In some cases the damage does not remain long as other parts of the brain are re purposed to fill the role of the damaged cortical tissue. Humans had been under the impression for the longest time that their ability to regenerate neurons in the CNS was lacking. However, in comparison to other species with similar cortical structures, this ability is astonishing.

Humans are the only species known to be able to survive damage to cortical tissue.

However, there is one great issue with the human brain, and that is its extreme use of energy requiring at least 20% of the body's energy overall to keep functioning. Additionally the human brain requires sufficient nutrition and hydration. Any number of these issues can impair functioning to such a complex organ.

To add to this, additional memory processing can only happen when paired with sleep.

Sleep is a construct not totally understood by the rest of the galaxy. While certain species are known generate phases of reduced consciousness similar to human "meditation", they do not demonstrate the complete shut-down of conscious function that humans do. For the complete functioning of this apex predator, the brain requires at least eight hours of unconsciousness. In comparison to similar cortical structures, the process of sleep in humans is comparable to only one thing.... Death in other species.

The ship was quiet, terribly silent with only the distant thrumming sound of the engines. It was an odd fact about human space life. Eight hours or more of a solar cycle, the humans lay silent and unmoving completely unaware of the world around them, lying as if dead.

After nearly a year aboard the ship, Krill had gotten used to the odd fact, though it never ceased to amaze him and slightly terrify him.

The first time this had happened, he had been horrified out of his mind.

It was his first day aboard the human ship, and he had spent the last 12 hours at Captain Vir's side taking a tour of the ship and getting to know the human crew. The humans had been terrifying, but they had also been friendly smiling at him with their sharp white teeth and predatory eyes. They had introduced him to their odd greeting behaviors "handshakes" and "high fives". To his additional surprise, the humans had wasted no time in making fun of their human counterpart for the loss of his eye, still bandaged and heavily monitored by Krill and the other medics aboard the ship.

Instead of feeling insulted the man had laughed and joined in declaring himself a "cyclops."

Interestingly, after a while, krill had noticed an odd behavior among the humans. They were slowing down, their eyes drooped, and occasionally one of them would open their mouth wide taking in a massive breath as they did so. A "Yawn" By one of them would begin a chain reaction to multiple other humans in the vicinity.

Eventually, the captain laid a hand on his arm, "Well Krill, that's the ship for you, now get some rest, if you have any questions, I will be in my quarters."

Following their captain's example, the rest of the crew slowly disbanded. The ship grew oddly quiet, and the humans had vanished.

Krill wandered about the ship marveling at the intricate structures and barbaric construction employed by the humans. He had so many questions, and he was sure one of the humans would be willing to answer it for him. The problem was finding a human, as it seemed, there was no one aboard the ships. The lights were dimmed eerily and there was not but the distant roar of the engines. Krill wandered around for some minutes opening doors and peeking inside, but finding nothing.

Eventually he made his way towards the crew's quarters peeping inside rooms and down hallways.

One door opened before him into darkness with a quiet hiss.

And what he saw there, froze him in fear an entire group of humans flat on their backs eyes closed unmoving in various poses of distress.

Some lay on their backs, others flat on their faces all completely unmoving.

Were they dead?

Krill backed from the room body thrumming with fear. What could have done this, what could have destroyed ten humans without so much as a fight or a scream? That couldn't be right.

He raced to the next door sliding it open with a hiss only to be caught by the same sight. Humans lying in the darkness unmoving mouths open, some of them leaking clear fluid.

Krill backed away again. This was terrible, horrible what could have gone wrong. He needed to tell the captain. He needed to warn someone. Turning, he deflated the hydrogen sack at his back giving him greater mobility to scurry down the hall and up the stairs to the captain's quarters. Even here, there were no sounds. He hurried down the hallway and towards the captain's door.

There came the same hiss as the door folded inward opening up into a darkening void.

Oh no.

And there he lay, curled up on his side knees drawn to chest. Krill would have guessed that the posture was defensive. His head was down chin covering the neck, his knees were drawn up blocking the exposed frontal organs.

Had something attacked him? Killed him as he defended himself here in the dark. Clear fluid oozed from the corner of his lips glittering dimly in the light. His body was colder than it had been before, he must have died recently.

Krill took a tentative step forward into the room, it was just him now, and he had to figure out what had happened.

He stepped a little closer foot knocking lightly into a boot discarded on the floor.

And the corpse jolted upwards.

Krill let out a shrill cry of horror. The corpse let off a similar yelp of surprise and leaped to his feet. A light flashed on somewhere. Krill staggered backwards tripping over the boot and falling to the floor.

The corps lurched around for a moment cursing covering its eyes before, "Krill?! What the F***! What's going on?"

Krill tilted his head in confusion, "Captain?"

"No, the Easter bunny. Yes it's me."

The human blinked a foggy green eye at him, "What the hell are you doing?"

"I..." Krill stammered, "The rest of the crew! I think they're dead!" He was shaking

The captain narrowed his eye in confusion, "Dead? All of them? Were they still breathing?"

Krill shook his head, "Well, they weren't moving.... That I could see, and their body temperatures were very low."

The captain paused and sat back on the squishy bench with a subdued chuckle, "Krill, the crew is asleep."

"Asleep." He asked in confusion

The captain nodded, "yes, asleep. It's when we shut our bodies down to like..... Reserving energy. It helps with learning, and memory, and it cleans things out. Speeds up the healing process" He motioned to his missing eye, "Very important if I want to avoid infection. And I need at least eight hours of it.... So if you don't mind?"

Krill shuffled awkwardly, "S-sorry captain."

The human waved him off as he returned to a supine position, "It's alright Krill. Never occurred to me that you guys didn't sleep. Everyone I know does it."

***

With permission from the captain, Krill had been allowed to run some tests in order to observe this "sleep".

Using advanced imaging techniques, krill was able to recreate what the humans felt and saw during these times, while also monitoring their physiological functions.

What he found was..... Terrifying.

The captain closed his eye and grew very still. At first there was nothing, but after a few minutes the heart rate began to slow dramatically. It dropped from 80 to 70 then to 60 at 58 Krill panicked waking the human with a sudden jolt and a curse.

"Human, are you ok?" He asked hesitantly.

"I won't be if you startle me like that again."

Krill bashfully let him go back holding himself back from waking the human as his heart slowed again. His breathing grew shallow. The body temperature dropped. Brain waves grew long and slow as the human fell even further.

He panicked again once the human's motor cortex locked up.

When the human awoke this time, he was more disoriented than he had been before groggy and bleary demanding to know what was going on, "This time."

"You were DYING." Krill screeched not understanding what the human didn't understand about that.

The human raised an eyebrow, "Um, no."

Krill nodded, he had only ever seen symptoms like that at the hospital right before death. First the body shuts down consciousness. Energy seeps out as heat, internal mechanisms begin to slow, the brain's function grows confused and erratic. Spaces that were once alive slow down while others jolt to life in an attempt to keep the body working. Eventually the motor strip is shut off to conserve energy. Those who have managed to come back from the brink report seeing terrible visions of reality and memory stitched together in terrible configurations.

Krill's study on human sleep would prove to be revolutionary.

***

The humans need death to survive.

Every night when the lights dim and the ship quiets, the humans willingly, and enthusiastically, slip towards the void taking their bodies and their minds to the very brink of death. Their body heat, their heartrate, and their breathing drop to unsustainable daytime level. Their body goes stiff and unmoving as they are assailed with these pre-death visions.

But do the humans fear this?

The answer is a resounding NO.

The humans revel in their nightly dance with the void.

They willingly slip in and out taunting the darkness for hours on end even as their bodies drawn energy from the blackness.

Their species evolved to drawn energy from death, to stare into the blackness and repair themselves, stronger, smarter, better as the black beckons. They have no fear, but joy, they find peace at the brink of the unknown perused by their own "reaper."

Tell a human these things, and they will laugh in your face. They know death on an intimate level so much so that they cannot fathom the similarities that we see. They do not just take joy in this nightly activity, but they NEED it, they pull their vitality from death. The longer a human goes without this nightly dance the more likely they are to succumb completely to the void.

We knew humans were a death-formed species, from a death world, worshiping death, and now we know why.

The young spend the greatest time here, children and babies, while the elderly spend less time as if aware of their proximity to the blackness.

The humans won't admit it, but there is proof of what we say. The hypnic jerk, as the humans coined it, describes the sudden violent wakefulness accompanied by an immense increase in body function and startle response. Some humans have gone so far as to suggest this is their cortical reaction to the brain confusing the process of falling asleep as dying.

What the humans don't understand is just how right they are.