question:  How were the Volpla able to eat solid food so quickly?
context: 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. I carried their limp little forms out to a mattress in the lab, two girls and a boy. 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 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. Even in the basically mutating colony, there had been a decidedly simian appearance in recent years, a long shift from the garbage-dump rats I had started with. But my first volplas were shockingly humanoid. They were also much faster than had been their predecessors in organizing their nervous activity after the slumbrous explosion of growth in the metabolic accelerator. Except for the face, chest and belly, they were covered with a soft, almost golden down. 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. Powerful wrist muscles could snap it outward and forward. Suddenly, as I teased the male volpla, this happened.
output:  Their growth had been artificially sped up, so they passed the stages where they would have needed different food
options:  Their anatomy is not human, and their more developed digestive system handles solid food much earlier  They mature very quickly, as a result of their mutant status, so it would be easy to eat anything  Their growth had been artificially sped up, so they passed the stages where they would have needed different food  Solid food was the only thing they were offered, so they learned to eat it