 What makes Johnson's son so different?
Then Johnson rubbed his thumb on his index finger and wetted his lips expectantly. "Johnson, as I saw instantly, is the victim of a difficult environment, and must charge accordingly." Him and me are the whole Earthman population of Johnson City." Johnson's eight-foot son, topped by a massive roof of sun-bleached hair and held up by a foundation that seemed immovable, had obviously been born and raised in low gravity. "What do you mean, once ?" demanded Johnson. "You'll find everything you want in the back room," Johnson said frantically, "sulfopyridine, mustard plasters, rubs, inhalers, suction cups—" "Relics of the past," Harvey stated. Astonished, Johnson and his son drew closer.
 He grew up without Earth's gravity, allowing him to grow larger than most people.
 He grew up without Earth's gravity, allowing him to grow larger than most people.  He is much larger than the average man.  Like Genius, he is not human.  He's been living isolated from other humans with his father.