Protagonist has traveled the world looking for signs of life in major cities, only to find them empty. Everyone else is dead of radiation poisoning and he was spared because of a special serum. All warm-blooded mammals are dead in Europe. He sails for The Middle East, "the land of the two great rivers." He walks until he encounters a land rich with all types of plants and animals. In his loneliness, he wakes up to find thw woman he has wished for sleeping beside him. The final line: "'I am Adam,' he told her, 'and you are Eve."
One page Cold War/Shaggy-God mash-up. Cribs from Shelley's The Last Man and Sheil's The Purple Cloud. Lands on the page with an audible thud.
Not listed in the ISFDB entry on Christopher. The story might have its only publication in Esquire, May, 1952.
See also "Two"