Final answer:
The ice ages forced early humans to move to new environments.
Step-by-step explanation:
The ice ages had the effect of forcing early humans to move to new environments (option c). During the ice ages, Earth's early peoples lived in colder temperatures and areas covered in ice. This created a scarcity of resources, such as edible plants, water, and game, which early humans relied on for survival. To ensure access to these resources, early humans formed small groups and migrated to different areas, adapting to different environments.