"It's a man-sized job we've tackled," commented the doctor. "What Smith says is true; such people would never stand for any measures which would restrict their physical freedom. They are simply animals with human possibilities, nothing more."
He paused, and then added quietly, "By the way, did either of you notice any mountains just now?"
Smith and Van Emmon both said they had. "Why?"
"Of course, it isn't likely, but—did you see anything like a volcano anywhere?"
"No," both replied.
"Another thing," Kinney went on. "So far, I've seen nothing that would indicate lightning, much less the thing itself. Did either of you," explicitly, "run across such a thing as a blasted tree?"
They said they had not. Billie hesitated a little with her reply, then stated that she had noted a tree or two in a state of disintegration, but none that showed the unmistakable scars due to being struck by lightning.
"Then we've got the key to the mystery!" declared the doctor. "Remember how brown and barren everything looks, excepting only where there's artificial vegetation? Well, putting two and two together, I come to the conclusion that Sanus differs radically from the earth in this respect.
"The humans have arrived rather late in the planet's history. Or—and this is more likely—Sanus is somewhat smaller than the earth, and therefore has cooled off sooner. At any rate, the relationship between the age of the planet and the age of its human occupancy differs from what it is on the earth."
"I don't quite see," from Smith, "what that's got to do with it."