Peru, situated between Ecuador to the north and Chile and Bolivia to the south on the Pacific coast of northwestern South America, has one of the most varied and complex set of eco-zones in the world.  A massive altiplano or high plain, studded with 6000-meter peaks, runs the length of the country paralleling the coast, north to broad south, at Lake Titicaca (3812 meters or about 12,700 feet above sea level) on the Bolivian border.  Streams and rivers running west to the Pacific Ocean today hold little water, as the great glaciers that fed them in the past have largely melted away, resulting in coastal desert.  One of the many downsides of global warming (whether human-induced or of exterior origin) is that many glaciers are rapidly shrinking on the great peaks of the altiplano , greatly reducing its moisture as well.

Within this complex set of Peruvian habitats, autochthonous populations have been speaking a hundred languages, or mutually unintelligible dialects, remnants of perhaps two or three hundred spoken at the time of Indo-European contact during the sixteenth century.  Somehow many of the languages continue to survive.  They are spoken from some 15,000 feet in the Andean ranges down to about 320 feet where the Amazon exits Peru to the east or to sea level on the Pacific coast.

South of Iquitos on the Amazon, two major tributaries flow from headwaters:  the Marañon to the west, exiting from the center of the Peruvian cordillera, and the Ucayali to the east, flowing just beyond the mountains.