Question

the evolving human skeleton
our early ancestors were hunter - gatherers who obtained food by hunting and by searching for edible wild plants. they needed strong bones, including large, strong jaws that enabled them to eat tough, uncooked foods. when our ancestors developed agriculture, however, their diet changed. they began growing plants, such as grains and beans, and raising animals for food; they also started cooking their foods, making them softer and easier to chew. consequently, the human skeleton underwent radical changes. over time, the human jaw became smaller and changed shape. other bones also evolved, becoming lighter, especially in the joints, as a result of both dietary changes and a less active lifestyle.
what is the main, or central, idea of the passage?
early humans ate uncooked meats and vegetables, so they needed strong jaws for chewing.
as early humans developed agriculture, their bones changed significantly.

Explanation:

The passage first describes early ancestors' skeletal needs as hunter - gatherers. Then it explains how the development of agriculture (diet change, cooking food) led to radical changes in the human skeleton (smaller jaw, lighter bones). The first option only focuses on the hunter - gatherer jaw need, while the second option captures the main idea of skeletal change due to agriculture development.

Answer:

As early humans developed agriculture, their bones changed significantly.