Final answer:
Brenda identified the introduction of agriculture as the transition from the Paleolithic to the Neolithic periods, which marked the beginning of settled agriculture and domestication of animals.
Step-by-step explanation:
The introduction of agriculture marks the change in periods from the Paleolithic to the Neolithic. During the Paleolithic Age, which began as early as 3.3 million years ago and lasted until about twelve thousand years ago, humans were predominantly hunters and gatherers. The subsequent Neolithic Revolution, which started roughly twelve thousand years ago, led to the adoption of agriculture and the domestication of animals, initiating the Neolithic Age. This transition allowed for larger human populations, development of food surpluses, and the beginning of labor specialization.
The Mesolithic Age served as a transitional phase between the Paleolithic and Neolithic periods, characterized by the warming climate and the retreat of glaciers. It was during the Neolithic Age that significant advancements were made in farming, and communities started to build complex structures like Stonehenge, indicative of a more settled and cooperative lifestyle.