Final answer:
The earliest settlers in South America were indigenous peoples forming agricultural societies around the third century BCE, followed by Spanish and Portuguese colonization from the sixteenth century onward.
Step-by-step explanation:
The first settlers in South America were indigenous peoples who transitioned from hunter-gatherers to complex agricultural societies around the third century BCE. Later, during the sixteenth century, European colonization began with the arrival of the Spanish and Portuguese explorers and conquistadors, with Spain focused on conquest while Portugal established sugar plantations in Brazil. The Spanish conquest led by figures like Hernán Cortés and Francisco Pizarro was marked by the search for wealth and military glory in the New World.
Indigenous societies such as those in the Andes and areas like Tiahuanaco laid the foundations for complex civilizations that were well established before European contact. The eventual subjugation and colonization of these civilizations resulted in a Spanish-dominated South American continent, with notable exceptions like Portuguese Brazil. These colonial powers significantly altered the demographics, economics, and cultural landscapes of South American societies, mixing with the local populations and creating a layered caste system reflective of the diverse ethnic backgrounds present at the time.