Gonna write a story, here's a description of it!
Jack awakes from deep-sleep expecting to have arrived in orbit of a distant world, but instead he finds that something has gone terribly wrong. The colony ship should have taken only a few hundred years to arrive at its destination, but he has been in stasis for much longer; many thousands of years, in fact. The ship has somehow missed its destination and flown right by, or perhaps veered off course and headed out into the unknown. It is now thousands of years into deep space.
After a thousand years of drifting through deep space, many of the ship’s systems began to fail. A power shortage resulted in some of the stasis chambers opening, and hundreds of passengers woke up to find themselves stranded. With limited supplies, surviving a life trapped aboard the ship wasn’t easy, but many of them managed to adapt. They split into several different groups based on their individual skills and how far they were willing to go to stay alive.
The farmers managed to grow their own food using the agricultural supplies intended for the colony, but there wasn’t enough to go around. Another group, made up of the remnants of the crew and some members of the military, were forced to be more creative. When the farmers refused to share their food, they turned to cannibalism. At first, they harvested the passengers whose stasis chambers had not yet malfunctioned, opening their stasis pods and killing them in their sleep. Later, as the food source became scarce, they began hunting the other survivors. While their numbers dwindled, both groups were able to adapt well enough to survive and breed, as were their children and grandchildren.
After many successive generations, the descendants of the passengers are now perfectly adapted to life aboard ship, some of them hideously so. The memory of life on Earth has become a half-remembered legend, and the word “humanity” no longer applies.