Final answer:
Humans lived as hunter-gatherers for the majority of their existence, relying on gathering plants and hunting wild animals for sustenance. This lifestyle was sustainable until the Neolithic Revolution, which introduced agriculture and enabled larger, more stable populations as well as the development of cities.
Step-by-step explanation:
For the majority of human existence, specifically around 150,000 to 200,000 years, people lived in hunter-gatherer societies and subsisted primarily by gathering wild plants and hunting wild animals. This way of life required that groups lived nomadically, moving from place to place in search of food, which was obtained through foraging for fruits, nuts, berries, roots, and hunting and trapping animals, or fishing in water bodies. Hunter-gatherers did not typically produce a significant surplus of food, meaning their populations remained fairly static due to the precariousness of their food sources. Over thousands of years, their subsistence strategies shaped their physical and behavioral evolution, favoring features that allowed for long-distance walking, a diet rich in plants, and social cooperation.
The hunter-gatherer lifestyle persisted until the Neolithic Revolution, about 10,000-12,000 years ago, when the development of agriculture led to more sedentary lifestyles and enabled the formation of cities and larger, more stable populations. This shift allowed humans to extract a greater proportion of energy from the environment, dramatically increasing the carrying capacity of the land and allowing population densities to soar. Over time, the reliance on gathering and hunting as the primary means of subsistence declined as agriculture spread. However, some groups continued to practice this lifestyle, and even today, a few hundred hunter-gatherer societies still exist, although they are rapidly diminishing.