 Max, who is nineteen when Scanlon saves and adopts him, is the oldest Tweenie in the story, which suggests that the existence of the Tweenies is a recent phenomenon.This in turn implies that interplanetary travel is also a recent phenomenon, an implication supported by Scanlon's description of pre-atomic trips to Mars and Venus as "hazardous gambles".Another implication of the Tweenies' presence on Earth is that the native Martians will not allow them to remain on Mars.