Through studying the physical remains of the past, sometimes with very new high-tech procedures such as DNA analysis, scholars have determined that human evolution involved a combination of factors, including bipedalism, larger brain size, spoken symbolic language, and longer periods of infancy. Humans invented ever more complex tools, many of which were made of stone, from which later scholars derived the name for this earliest period of human history, the Paleolithic era. These tools allowed Paleolithic peoples to shape the world around them. During this era, humans migrated out of Africa, adapting to many different environments and developing diverse cultures. Early humans lived in small groups of related individuals, moving through the landscape as foragers in the search for food.

Beginning about 9000 B.C.E. people living in southwest Asia, and then elsewhere, began to plant seeds as well as gather wild crops, raise certain animals, and selectively breed both plants and animals to make them more useful to humans. This domestication of plants and animals was the most important change in human history and marked the beginning of the Neolithic Era. The domestication of large animals led to plow agriculture, through which humans could raise much more food, and the world’s population grew. Plow agriculture allowed for a greater division of labor, which strengthened social hierarchies based on wealth and gender. Neolithic agricultural communities developed technologies to meet their needs and often traded with one another for products that they could not obtain locally. Religious ideas came to reflect the new agricultural society.