Final answer:
Large mammals often evolve smaller sizes on islands due to 'island dwarfism,' a process driven by limited resources and the absence of key predators.
Step-by-step explanation:
The phenomenon of large mammals evolving smaller body sizes on islands compared to their mainland counterparts is known as island dwarfism. This process occurs because islands typically have more limited resources and sometimes lack the key predators that would otherwise drive animals to maintain larger sizes. For smaller animal species that colonize islands, an increase in body size may occur if there is an absence of larger predators. However, for larger species, a reduction in size is often advantageous due to the limited availability of resources, which can include food, space, or safe habitats. The principle of island dwarfism explains how species like Homo floresiensis and the dwarf elephant species Stegodon could have evolved from larger ancestors to fit the constraints of their island environment.