question:  What motivated the narrator to design the Volpla origin story as he did?
context: Volpla By WYMAN GUIN Illustrated by [Transcriber's Note: This etext was produced from Galaxy Science Fiction May 1956. The only kind of gag worth pulling, I always maintained, was a cosmic one—till I learned the Cosmos has a really nasty sense of humor! Volplas at last. Yet I had always been so sure I could create them that I had been calling them volplas for ten years. I had called them volplas since the day old Nijinsky's elongated arms and his cousin's lateral skin folds had given me the idea of a flying mutant. Again in the laboratory, I entered the metabolic accelerator and withdrew the intravenous needles from my first volplas. The accelerator had forced them almost to adulthood in less than a month. It would be several hours before they would begin to move, to learn to feed and play, perhaps to learn to fly. Meanwhile, it was clear that here was no war of dominant mutations. I thought, "All this and three volplas, too." I wiped the back of my hand across my mouth and said aloud, "Yes, sir, the dangerous age. I kissed her until I heard rollerskates coming across the terrace from one direction and a horse galloping toward the terrace from the other direction. Outside this little town, I found a litter of flat stones that had young black-snakes under each slab. But my first volplas were shockingly humanoid. Except for the face, chest and belly, they were covered with a soft, almost golden down. On their heads and across the shoulders of the male stood a shock of fur as soft as chinchilla. The cranium was in the same proportion to the body as it is in the human. The spars had been common to the basic colony for years and were the result of serial mutations effecting those greatly elongated fifth fingers that had first appeared in Nijinsky. No longer jointed like a finger, the spar turned backward sharply and ran alongside the wrist almost to the elbow. Suddenly, as I teased the male volpla, this happened.
output:  Making them think they were aliens was part of preventing any traceable ties between them and himself
options:  He enjoyed creating backstories for the creatures as part of the stories he told them  He did not want the creatues to feel like they did not have a rich history  The Volpla asked him to tell them their history, and when they guessed they were from elsewhere, he ran with it  Making them think they were aliens was part of preventing any traceable ties between them and himself