Who's your paddy? A new study by American researchers announced in the May 3rd, 2011 issue of the Proceedings of the National Academy of Sciences (PNAS) has finally put to rest an old debate about an ancient grain: domestic rice originated in China. It had previously been thought that domesticated rice in all its many modern day varieties could be traced back to two points of origin: China and India.
Japonica and Indica, the two major subspecies of Asian rice (Oryza sativa), represent most of the world's domestic rice, but various degrees of hybridization with other domestic rice varieties and with wild rice over thousands of years have clouded the issue of rice's ultimate origin.
The research team that included New York University biologist Michael Purugganan concluded that today's Japonica and Indica rice varieties are genetically closer to one another than to any of the wild rice species native to either India or China.
“As rice was brought in from China to India by traders and migrant farmers,” explained Purugganan, “it likely hybridized extensively with local wild rice. So domesticated rice that we may have once thought originated in India actually has its beginnings in China.”
Location is one thing, timing is another. Investigators using a “molecular clock” of rice genes were able to pinpoint the origin date for domesticated rice to be approximately 8,200 years ago. Japonica and Indica rice, on the other hand, split from their common ancestor into two distinct varieties a mere 3,900 years ago.
The date provided by the molecular clock jibe with previously determined estimates of rice domestication provided through hands-on archaeological methods. Those estimates peg the beginning of rice farming in China to the Yangtze Valley roughly 9,000 years ago. (via Global Times and Peace-On-Earth)