"My gift to industry is the genetically engineered worker, or Genejack. Specially designed for labor, the Genejack's muscles and nerves are ideal for his task. And the cerebral cortex has been atrophied so that he can desire nothing except to perform his duties. Tyranny, you say? How can you tyrannize someone who cannot feel pain?" -Chairman Sheng-Ji Yang, "Essays on Mind and Matter"
The Genejack is a genetically engineered human laborer invented by the leader of the Human Hive, Chairman Sheng-Ji Yang. They were created shortly after the advent of Retroviral Engineering. By utilizing manufactured viruses, Yang was able to create the perfect worker by rewriting human DNA.
The Genejacks were used to crew the massive Genejack Factories, manufacturing facilities that, unlike other factories, used slave labor instead of industrial robotic assembly units. Genejacks were well suited to manual labor, as they possessed great strength and endurance. They serve unquestioningly, in fact, they are incapable of questioning their orders, as their cerebral cortex was atrophied to inhibit higher thought and eliminate emotions. Utilizing Genejack Factories can provide a fair mineral (production) bonus, but the mentally-deficient Genejacks will add to a base's Drones. One may choose to avoid building Genejack Factories until they are able to reduce the Drone population.