“… the evidence that the Ainu did not once make pottery is only negative ; they certainly never did in historical times, but that does not of itself prove anything ; they may have had the art and lost it after contact with the more advanced race, as witness several tribes of our own Indians. Their own legend on the subject is this : Once, a very long time ago, an old Ainu woman was struck with the idea of makina- vessels out of clay, and she actually did make one. She was so delighted with it that she started out for the village to show it to her neighbors ; but on the way it dropped and broke all to pieces, and she was so disgusted that she never made another. …
This story has an air of having been invented to account for something the Ainu were rather ashamed of, like the one which relates how a stranger came from no one knew where, and stayed with Okikurumi, and taught him several things, such as rowing with two oars instead of paddling, but who finally ran away with Okikurumi’s wife and his two treasures, a book and a counting board, and thus is why, ever since, we, Ainu have not been able to read.”
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Anna Hartshorne,http://archive.org/stream/japanherpeople02hart/japanherpeople02hart_djvu.txt
JAPANESE MYTHOLOGY & FOLKLORE 