Early humans were nomadic hunter-gatherers, relying on hunting animals and gathering plants for sustenance.

Agriculture first emerged in Mesopotamia (modern-day Iraq) around 10,000 BC, with the cultivation of wheat and barley.

Agriculture was the backbone of the economies of ancient Greece and Rome, with crops such as wheat, barley, and olives being widely cultivated.

The invention of the compass in the 12th century enabled more accurate navigation, leading to increased trade and exploration.

Feudalism was the dominant economic system in Europe during the Middle Ages, characterized by a hierarchical structure with lords, vassals, and serfs.

The Industrial Revolution began in the United Kingdom in the late 18th century, with the invention of new technologies such as the steam engine and the mechanization of textile production.

Classical economics, associated with economists like Adam Smith and David Ricardo, promoted free trade and limited government intervention as the best way to achieve economic growth.

Keynesian economics, developed by John Maynard Keynes, argued that government spending and fiscal policy could stimulate economic growth during periods of economic downturn.

Agriculture was the dominant economic activity in the United States during the 19th century, with crops such as cotton, tobacco, and wheat being widely cultivated.

Institutional economics, associated with economists like Thorstein Veblen and John R. Commons, emphasized the role of institutions and social factors in shaping economic outcomes.

Services became the dominant economic activity in the United States during the 20th century, with sectors such as healthcare, education, and finance experiencing rapid growth.

Endogenous growth theory, developed by economists like Paul Romer and Robert Lucas, emphasized the role of technological progress and innovation as key drivers of economic growth.

Services continue to be the dominant economic activity in the United States during the 21st century, with sectors such as information technology, healthcare, and finance playing a major role.

Human capital theory, developed by economists like Gary Becker and Theodore Schultz, emphasized the importance of human capital, education, and skills in driving economic growth.