Final answer:
Humans adapted to climates unsuitable for intensive farming through the adoption of agriculture, which allowed for surplus food production and specialization within societies, ultimately leading to the growth of cities and early civilizations.
Step-by-step explanation:
The economic system that permitted humans to adapt in larger numbers than ever before to climates where intensive farming was not possible is agriculture. Prior to the adoption of agriculture, humans were hunter-gatherers who had to follow food sources, living as nomads. With the agricultural revolution, around 10,000 BCE, humans began the deliberate cultivation of edible plants and the domestication of animals, which allowed for a more settled lifestyle and the growth of larger communities. Agriculture led to a surplus of food and other materials, which in turn permitted the development of specialization and trade within societies.
This surplus of food supported larger family sizes and ultimately led to the growth of cities and early civilizations. People could focus on performing specific tasks, such as crafting or trading, because they relied on the food produced by farmers in rural areas. This system of exchange was a pivotal feature of early civilizations, marking a significant evolution from previous societies that were reliant on hunting and gathering techniques.
The advent of agriculture was spurred by a warming climate post the last ice age, leading to a fundamental change in human life. The increased caloric energy from agriculture allowed for dramatic increases in population levels and family sizes, which further fueled technological advancement and economic development.