Final answer:
The environment crucially shaped the life of early humans in the Americas by dictating resource availability, enabling the development of agriculture, and leading to the cultural diversification of isolated groups until the time of European contact.
Step-by-step explanation:
The environment profoundly influenced life for early people in North and South America. The end of the last ice age around seventeen thousand years ago dramatically changed the Earth's landscape, submerging continental shelves, and creating new lakes and rivers. Such environmental transformations allowed for the exploitation of marine life, affected the movement and types of animals available for hunting, and ultimately led to the isolation of human populations in various regions. For instance, those in maritime Southeast Asia and Australia became secluded on islands, while those in the Americas were cut off from the Eastern Hemisphere populations due to rising sea levels in the Bering Strait.
As the global climate changed and warmer temperatures prevailed, early humans adapted to their surroundings through subsistence hunting and gathering. They formed small tight-knit groups and migrated to ensure access to resources. Geographic features, climate conditions, and the availability of natural resources determined whether societies were nomadic or settled agriculturally. The retreat of glaciers and subsequent environmental changes set the stage for the development of agriculture and complex societies in the Americas.
Prehistoric North America saw the transition from Paleo-Indians, focused on hunting megafauna, to periods of plant domestication and agriculture, exemplified by the cultivation of the Mesoamerican triad of corn, beans, and squash. The introduction of agriculture supported the growth of complex towns and cities, like the Mississippian Cahokia, and regional geography continued to shape various groups, as seen with the buffalo-reliant Plains societies.
Overall, the environment had a critical impact on life for early people, dictating survival strategies, influencing the development of cultures, and separating the Americas from the broader course of human history until European contact.