Thanks for the feedback, much appreciated.
Been doing more research and the long shaft was likely made of bull pine (also know as grey pine, and a derogatory name attributed to natives of California which I wont repeat). The immature trees grow nice and straight, few offshoot branches, and holds massive amounts of sap (which is why its not logged for lumber). That heavy sap would have been useful in providing some degree of waterproofing is my guess. The trees grow all around me, and I can see that finding one with a closely symmetrical fork in it would have been very difficult, if not impossible.
I've got the cordage material collected (dogbane), next step is find a straight 12' long bull pine, cut it, and dry.