Investigation of dark earths from two archaeological sites near Araracuara, on the Río Caquetá in Colombian Amazonas, indicates that these soils are anthropic, with characteristics similar to those of the terra preta soils of the Brazilian Amazon. The Araracuara sites belong to the Camani (plainware) phase of the second to ninth centuries A.D. and to the Nofueri phase (ninth to seventeenth centuries) with pottery of the Polychrome Tradition. The Araracuara examples are the first archaeological terra preta soils analyzed from west of Brazil, although similar materials are reported from Ecuador and Peru. The problems of recognizing and dating the first appearance of terra preta soils are discussed, and a plea is made for closer collaboration between archaeologists and soil scientists.