When an animal population is limited to a very small environmental area, its members may become reduced in size. This phenomenon, known as insular dwarfism, is most common on islands but may also occur in caves and isolated valleys. Experts remain divided on what causes this dwarfing. One theory is that it is a gene-encoded response to environmental stress; another is that smaller animals have a survival advantage when food is scarce. What extinct and extant species have undergone this process? Discuss