>Ishige seems to imply that it wasn't that rice cultivation came to Japan
>during the Yayoi period, but that the tools and social systems neccessary
>to make it a profitable system of agriculture developed in that time. She
>goes on to mention that: "In the east, where a stable culture centred on
>acorn gathering was flourishing, there was very little incentive to hazard
>a switch to an unknown lifestyle of agriculturalism."
Japan is one of the most fertile temperate zones on Earth. Being a
hunter/gather requires little effort and large populations can be
supported. One book that I read suggested this for the reason why the
Japanese were so late in taking up agriculture. There was no need to do
all that hard work. As pointed out, it's possible that rice was raised
as a special item for the nobility before it's common introduction.