<P> There is ample evidence that the areas surrounding the Amazon River were home to complex and large - scale indigenous societies, mainly chiefdoms who developed large towns and cities . Archaeologists estimate that by the time the Spanish conquistador De Orellana travelled across the Amazon in 1541, more than 3 million indigenous people lived around the Amazon . These pre-Columbian settlements created highly developed civilisations . For instance, pre-Columbian indigenous people on the island of Marajó may have developed social stratification and supported a population of 100,000 people . In order to achieve this level of development, the indigenous inhabitants of the Amazon rainforest altered the forest's ecology by selective cultivation and the use of fire . Scientists argue that by burning areas of the forest repetitiously, the indigenous people caused the soil to become richer in nutrients . This created dark soil areas known as terra preta de índio ("indian dark earth"). Because of the terra preta, indigenous communities were able to make land fertile and thus sustainable for the large - scale agriculture needed to support their large populations and complex social structures . Further research has hypothesised that this practice began around 11,000 years ago . Some say that its effects on forest ecology and regional climate explain the otherwise inexplicable band of lower rainfall through the Amazon basin . </P> <P> Many indigenous tribes engaged in constant warfare . James Stuart Olson wrote: "The Munduruku expansion dislocated and displaced the Kawahíb, breaking the tribe down into much smaller groups...(Munduruku) first came to the attention of Europeans in 1770 when they began a series of widespread attacks on Brazilian settlements along the Amazon River ." </P> <P> In March 1500, Spanish conquistador Vicente Yáñez Pinzón was the first documented European to sail up the Amazon River . Pinzón called the stream Río Santa María del Mar Dulce, later shortened to Mar Dulce, literally, sweet sea, because of its fresh water pushing out into the ocean . Another Spanish explorer, Francisco de Orellana, was the first European to travel from the origins of the upstream river basins, situated in the Andes, to the mouth of the river . In this journey, Orellana baptised some of the affluents of the Amazonas like Rio Negro, Napo and Jurua . The name Amazonas is taken from the native warriors that attacked this expedition, mostly women, that reminded De Orellana of the mythical female Amazon warriors from the ancient Hellenic culture in Greece . </P> <P> Gonzalo Pizarro set off in 1541 to explore east of Quito into the South American interior in search of El Dorado, the "city of gold" and La Canela, the "valley of cinnamon". He was accompanied by his second - in - command Francisco de Orellana . After 170 kilometres (110 mi), the Coca River joined the Napo River (at a point now known as Puerto Francisco de Orellana); the party stopped for a few weeks to build a boat just upriver from this confluence . They continued downriver through an uninhabited area, where they could not find food . Orellana offered and was ordered to follow the Napo River, then known as Río de la Canela ("Cinnamon River") and return with food for the party . Based on intelligence received from a captive native chief named Delicola, they expected to find food within a few days downriver by ascending another river to the north . </P>

Where does the amazon river water come from