The first people probably arrived on the Atlantic coast of South America about 15,000 BC, following the Atlantic coastline south from Central America. Probably a second wave of people followed them around 11,000 BC. It’s also possible that other people reached South America by boat from Australia or Indonesia.
As they followed the coast south with their dogs, these people lived mostly on seaweed, shellfish, shrimp, and fish, which they preserved by fermenting them in baskets lined with clay so they would hold salty water. This is the same way people preserved fish in Japan, and possibly these people brought their baskets and their love of pickled fish with them from northern Asia. By around 5500 BC, Brazilians were making pottery jars to pickle their fish in. Slowly they spread out along the banks of the Amazon river, moving away from the coast further inland. Some towns along the Amazon had tens of thousands of houses. And it wasn’t all fish, all the time: these people also ate peanuts, cacao beans, and yuca roots (a starchy root like a potato) and leaves, among other things.
The Tupi people, on the other hand, came south from Central America and settled in the center of South America. They may have been the ones who domesticated yuca root, about 10,000 BC. The Tupi made most of their tools out of wood or bone, because flint and obsidian were rare in central South America. About 900 BC, the Tupi began to conquer south and east towards the coast. Starting around 500 BC, some of them went further south into Paraguay, conquered the people there, and became the Guarani. Other Tupi people conquered the big towns along the coast of Brazil and settled there. Many of the conquered people, who we call the Tapuias, had to move further inland, away from the coast, though some stayed along the coast too.
These big Tupi and Tapuia towns, and their rulers, sometimes got into wars. They may have been fighting over who got to live on the coast where the fish were, and who had to live further inland. Around this same time, a lot of these people began to farm some of their food. In the south (modern Argentina), they farmed corn that they may have gotten from the Guarani to their east. Further north (in modern Brazil), they farmed yuca root, and in the mountains along the Argentinian coast people used irrigation to farm peanuts. All these people also farmed beans, sweet potatoes, chili peppers, and yams. But they also kept on eating a lot of seafood and seaweed, making huge piles of seashells along the coast.