What's more intriguing is that we know for sure that Polynesians did know about the bow, and at least some of them even knew how to make it - but, for whatever reason, it wasn't used for anything "serious" like warfare.

It's tempting to chalk it down to some kind of strong cultural taboo, e.g. to keep the wars at a "manageable" level of destruction. But then why did Maori eagerly adopt firearms once they got access to them, and used them in warfare between themselves?