Credited to Brazil. The domestication zone straddles present-day Brazil (northern Mato Grosso, Rondonia and Acre) and adjacent northern Bolivia, and the earliest archaeological remains come from coastal Peru, so the origin is shared rather than exclusively Brazilian.
How it began
Genetic studies trace cassava, Manihot esculenta, to a wild relative, Manihot esculenta subspecies flabellifolia. A review of native Amazonian crops places the start of domestication somewhere in the northern part of Mato Grosso, Rondonia and Acre states in Brazil and adjacent areas of northern Bolivia, in southwestern Amazonia. The same review states that domestication began before 8,000 years ago. A popular history of the crop gives a range of roughly 8,000 to 10,000 years ago for the same region.
How it works
Selection by farmers produced two broad groups. Sweet manioc has low levels of cyanogenic compounds, under 50 parts per million of fresh weight, and can be eaten safely after simple preparation. Bitter manioc contains much larger amounts and has to be detoxified and processed before it is eaten. Bitter varieties are associated with the main Amazonian rivers and coastal areas, where populations were denser, while sweet varieties are the main crop in the headwaters of western Amazonia, along the southern edge of the basin and in Mesoamerica.
How it spread
The crop dispersed quickly from its area of origin. It appears in the archaeological record of the Pacific coast of Peru, in the Zana and Nanchoc valleys, by about 8,000 years ago or earlier, and in southern Mesoamerica by 5,600 years ago at the latest. A genomic study of landraces in the Brazilian Amazon found that bitter and sweet manioc are genetically distinct and appear to have had independent dispersal histories, shaped by traditional farming practices.
Where it stands today
Researchers studying manioc in the Brazilian Amazon describe the genetic diversity held in traditional landraces as important for climate resilience and food security. Their work compares cultivated plants with wild populations to find signatures of selection left by domestication, and it treats the practices of Amazonian farmers as the reason that diversity still exists.
