Final answer:
Environmental changes including climate shifts and the extinction of dinosaurs greatly influenced the age of mammals. Warmer temperatures increased plant diversity, providing more food sources. Human activities such as hunting and deforestation altered ecosystems, which further shaped mammalian evolution.
Step-by-step explanation:
The worldwide environmental changes that set the stage for the age of mammals primarily entailed significant alterations in climate and vegetation. One key event was the mass extinction approximately 65 million years ago, likely caused by a large asteroid collision. This catastrophic event led to the demise of the dinosaurs and enabled mammals to proliferate.
Subsequent climate changes occurred during various periods. For instance, approximately 50 million years ago, a spike in Earth's temperature contributed to a proliferation of plant diversity, providing abundant food for mammals and their prey. Rapid climate changes during the late Quaternary resulted in the growth and retreat of continental ice sheets, reshaping habitats, particularly in the northern hemisphere. These fluctuations challenged ice age mammals, as well as early humans, to adapt or relocate, fundamentally affecting their survival and distribution.
Lastly, human-induced changes to the environment began to emerge with early hunters and farmers, leading to significant ecological impacts such as the extinction of megafauna and the clearance of vast forests. Because of these climatic and anthropogenic influences, mammals have undergone considerable diversification and evolutionary changes over millions of years.