A school of fish is separated into a small pond and a large pond. In the large pond, the tails of the males are decorative and have an average length of 6 cm; the fish must also avoid predators that live in the pond. In the smaller pond, the tails of the males are decorative and have an average length of 10 cm; however, there are no predators present. The females favor the longer, decorative tails. Male and female fish from a large pond are captured and placed into a small pond where there are no other predators. Which of the following best predicts and explains how the average tail length in males might change over many generations when the group of fish moved to the new small pond?