I loved 2001's idea of lunar exploration turning up a discovery capable of getting the entire scientific community excited, and unashamedly stole it. Science had long appealed to me as a glorious, ongoing detective mystery. Mysteries have dead bodies that need accounting for, so I made the discovery that of a body--found dead, in a space suit, on the Moon. To get scientists interested and excited would take more than footprints and blunt instruments, however. It turned out that "Charlie" had been there for forty thousand years.
Charlie is fully human in every respect. The question, of course, is, where did he come from? Logic allows only two possibilities: (1) Earth; (2) somewhere else. But (1) would imply the existence of a spacegoing civilization long ago, which is rejected due to the absence of any artifacts or other evidence. (2), on the other hand, requires two independent evolutionary lines to produce identical end products, which is also rejected as untenable. Therefore Charlie can't exist. But he's lying right there, on the slab.
The story relates the unraveling of Charlie's origins from the clues available. And the scientists reconstruct a remarkably detailed picture of the world that Charlie came from. The only problem is, half the evidence seems to indicate that it must have been Earth, while the rest says that it can't have been. Obviously I'm not going to spoil things by giving away the final resolution here, but as per the terms of the original bet, it all makes sense in the end.
See Dr. Attila Torkos' Giants Chronology for a timeline, recently updated to include all five novels. Click here to view the HTML version on-line, or right-click here to download an Adobe Acrobat PDF file, nicely formatted for printing.