Transadapts, aka "trolls", were humans genetically altered to live and work in low-gravity environments like space stations and other planets.
They were shorter than normal (about 4 feet tall) and resemble chimpanzees - hunched-over posture, low brow, long arms, and feet with opposable thumbs and nine long toes suitable for grasping. They were also immensely strong, far more so than their size would suggest. A large population was created to work on the space station Parallax Red and the Cydonia One colony on Mars; after the station was badly damaged during skydark, everyone (humans and trolls) fled to the Mars colony. Most of the transadapts were killed in a rebellion in the colony incited by Sindri, and the rest serve him.