The Eternal Wall by Raymond Z. Gallun description:
A scream of brakes, the splash into icy waters, a long descent into alkaline depths … it was death. But Ned Vince lived again–a million years later!
other star systems are not really your kind anymore, though their forefathers originated on this planet. They have gone far beyond you in evolution. To them you would be only a senseless curiosity. You are much better off with my people–our minds are much more like yours. We will take care of you, and make you comfortable…."
But Ned Vince wasn't listening, now. "You are the only man left on Earth." That had been enough for him to hear. He didn't more than half believe it. His mind was too confused for conviction about anything. Everything he saw and felt and heard might be some kind of nightmare. But then it might all be real instead, and that was abysmal horror. Ned was no coward–death and danger of any ordinary Earthly kind, he could have faced bravely. But the loneliness here, and the utter strangeness, were hideous like being stranded alone on another world!
His heart was pounding heavily, and his eyes were wide. He looked across this eerie room. There was a ramp there at the other side