There are times when you feel you are witnessing the precise moment when science fiction crosses over into science. I don’t mean the advent of gadgetry like voice-recognition software or flat-panel computer monitors, or even the coming of space tourism, but a moment when one of the great, enduring conundrums of our speculative literature suddenly materializes as an actual human situation. Perhaps the greatest of these is the problem of distinguishing humans from robots—what unique element, if any, separates us from machines?—a theme that received its classic treatment by Isaac Asimov in his 1946 story “Evidence.” In the story,…