The checkered prehistory of rice movement southwards as a domesticated cereal-from the Yangzi to the Equator

This paper discusses the origins of Oryza sativa japonica rice cultivation in the Yangzi region of China and asks how and with which migrating human populations it spread south to reach Taiwan by 3,000 BC and Southeast Asia by 2,000 BC. The perspective adopted is that the spread of rice was driven mainly by demographic expansion, associated with a spread of languages and archaeological material culture. Environmental barriers also played major roles in establishing a "pause, adapt, spread, pause again" mode of movement, such barriers relating to availability of rainfall and alluvial land, latitude (photoperiodism) and climatic seasonality, and the prior presences of other populations, in some cases with vegetative gardening systems that did not involve rice or other cereals. Contingency also played its part in rice history, as we can see with the inability of this crop to spread into Oceania in part due to the route followed by Neolithic colonizers.