Final answer:
Rodents' incisors continuously grow to compensate for the wear from their gnawing diet, whereas pigs and humans have teeth that stop growing after development due to their omnivorous diets that don't require excessive gnawing.
Step-by-step explanation:
The incisors of rodents, such as mice and rats, grow continuously because they are adapted to a gnawing diet that grinds down their teeth.
These animals constantly gnaw on various items, which would wear their teeth down; thus, the continuous growth compensates for the wear.
Unlike rodents, pigs and humans don't have this adaptation because their diets mainly include foods that do not require such excessive gnawing, and therefore their teeth, including their incisors, stop growing after reaching a certain stage, fitting their omnivorous diets.
Pigs and human incisors grow only during their development stage and, once adult size is achieved, they do not continue to grow. This difference in dental growth patterns correlates with the respective diets and feeding behaviors of these animals.