The Andean civilizations were South American complex societies of many indigenous people. They stretched down the spine of the Andes for 4,000 km from southern Colombia, to Ecuador and Peru, including the deserts of coastal Peru, to north Chile and northwest Argentina. Archaeologists believe that Andean civilizations first developed on the narrow coastal plain of the Pacific Ocean. The Caral or Norte Chico civilization of coastal Peru is the oldest known civilization in the Americas, dating back to 3500 BCE. Andean civilizations are one of at least five civilizations in the world deemed by scholars to be "pristine." The concept of a "pristine" civilization refers to a civilization that has developed independently of external influences and is not a derivative of other civilizations.