Everyone thought snake was a half human half snake hybrid. Of course, if they thought about it that was "impossible." Snakes were reptiles and humans were mammals. The two could not mate. Naturally.
No, Snake was born in a laboratory, a laboratory that specialized in creating "impossible" creatures. Snake was known at the time as TSMRHS9547, meaning Test Subject Mammal-Reptile Human-Snake number nine-thousand, five-hundred and forty seven. Many other part-human part-snake brothers and sisters had gone before him, nine-thousand, five-hundred and forty six to be exact. Most of them died even before conception, many others dying in their human wombs, killing the mothers as well. Eventually the scientists created an artificial womb, to prevent the deaths of human mothers. Women were very expensive and hard to replace.
He grew up in this laboratory, fed well, bathed and taken care-of, well, he had to deal with the tests and observations, but he had no knowledge of the outside world. He didn't even know it existed. This was his life, with little human contact. He was taught to speak and understand English, but punished when he spoke unless told to. He knew how to speak snakish, having been born with his vocal cords able to produce both the ranges of hisses snakes used and the sounds humans made. The doctors loved him, he was the first of his kind, he was a break-through for the ages! But he was not the last subject they created. TSMRHS9548 was made just after Snake was conceived, born a few days after Snake as a girl. As they grew, barely catching sight of each other once a week, TSMRHS9547 easily overcame Snake in the eyes of the doctors, and they threw him in "the closet."
"The closet" was where they put all the "failures," the ones that were no longer needed, or to dangerous to handle. It was a large room, with no windows except for the one-way mirror and a single door. The walls would have been pure white, Snake could tell, if not for the blood stains everywhere. It was a crowded room, test subjects packed so tight they couldn't move. The doctors never came in, for fear of their lives. They all watched from the one-sided mirror as the test subjects tore each other apart, limb from limb and devoured each other in attempts to live just a week or two longer. There was no food in "the closet," just the part-human part-animal...
Things.
Even though Snake knew for some reason that he shouldn't like being in the closet, he found it somewhat comforting. Snake didn't like being alone.
Snake lasted a few weeks in that hell-hole before one of the predators higher on the food-chain set it's eyes on him. This was a room with no morals, sickness and despair. As all animals discover through natural urges, one of the older, dead test subjects had discovered sex. All the others were still to young to have the urges yet. This test subject, TSMMHL993, part lion, raped his victims before devouring them. The other test subjects discovered that this "felt good," so they did it as well. The hell on Earth ravaged by murder, rape, sickness and part-cannibalism was where Snake lived for almost a month, before it happened.
Now, snakes are very nimble creatures, able to move with just their body weight, and hawks are their natural predator. TSMAHH1294 died of a sickness a few days after Snake was thrown into "the closet," much to Snake's relief. But being in that room also meant other creatures that would attack him. The top of the food chain at that time was TSMDRHT5011, a Tyrannosaurus-Rex hybrid. He took out all the major predators and was on to the minor ones. Starting with Snake.
TSMDRHT5011 stalked over to Snake one day, glaring and showing his large, jagged teeth, "Turn around and bend over, Snake-man, I'm going to fuck you and eat you," TSMDRHT5011 said, in his native tongue. TSMDRHT5011 was stupid, just like the Tyrannosaurus-Rexs' of old. Snake looked up at the half-man, startled and scared, though he would never show it on his face. "I said, turn around and bend over, bitch!" TSMDRHT5011 screamed, slapping Snake across the face. Snake scampered away, hiding behind a half-squirrel. TSMDRHT5011 roared, slapping the half-squirrel across the room. The half-squirrel smashed against the one-way mirror, shattering it to pieces. All the half-humans stared at the broken glass. Snake, taking the opportunity, jumped out the hole in the wall and ran down the hall to a door. TSMDRHT5011 chased after him, still thinking about dinner as the others scampered around, trying to find a place to hide. Snake passed corridor after corridor, finally finding a window with bright sunlight coming from it. He stared, temporarily awe-struck. TSMDRHT5011 followed closely behind, stopping as soon as he saw the green grass and blue sky. Two doctors ran down the hallway, dart guns in hand. Snake saw them first and broke through the window, running as fast as he could. TSMDRHT5011 quickly followed him, still thinking about dinner. The doctors aimed at TSMDRHT5011, not even thinking about Snake, he was more human and less of a problem. They could find him later.
Snake ran as fast as he could on this foreign grass, something he had never seen before. Behind him TSMDRHT5011 crashed to the ground, enough sedative to make a dinosaur go unconscious instantly pumping through his veins. The doctors chased after Snake, but he was much faster than these old men, and aiming at moving targets with their bad eyes was impossible. Snake had escaped to this outside world he'd never seen before, a world he didn't know.