Shell middens along the Brazilian coast, north of Rio de Janeiro. The oldest debris was left by non-agricultural peoples who used no pottery and who made artifacts of chipped and polished stone (axes, adzes, choppers). The middens are of widely differing ages, from the 6th millennium BC until the centuries before the European conquest. There are also well-finished polished stone effigies (usually of birds or fish) which have a basin-like depression in the back. Probably of ceremonial significance, it has been suggested that these effigies were used in the ritual taking of snuff.