The history of knitting is mostly a big mystery, guessed at from fragments kept in museums around the world. Knitting is made of wool, silk, and other fibers that decay rapidly, even under perfect conditions; knitting needles are essentially sharpened sticks, and hard to identify as knitting needles beyond a doubt; they could be hair picks, skewers, spindles, or any of the other zillion uses there are for a sharpened stick. In the past, when spinning was all by hand and much more time-consuming, many sweaters that didn't fit were raveled and re-knit. Yarn wasn't discarded until it wore out. Add in that not many people in the past thought to save their everyday items for their descendants, and there aren't many useful knitted objects left for us to find, all these years later. Once in a while we get lucky. The archeological evidence we have is very interesting, and there are other ways to date things.