As a prehistoric archaeologist i'm not so persuaded, because, if is true that in New Guinea there are a lot of these bone daggers, in the prehistoric Europe there aren't! Are usual to find awls, spatulas, and bigger awls to pierce leather all in bone but no daggers (and they could or couldn't show the epifisi - extremity- that recall the eared handle). Usually the prehistoric daggers are made of flint or obsidian. Unfortunatly in the majority of cases the handle is gone but in some sites, where the conditions are favourable (usually in lake sites) the handle is made of wood and in simple shape (never seen eared handle). It's also a conviction that all the objects that we can call weapons (like bow and arrows and daggers) untill the Copper age-Bronze age were used only as tools (or at least the main utilization was as tool, but no one knows if sporadically were used also as weapons). Only in the Bronze age (around 2000 b.c.) appear objects like swords (in the Copper age there are some daggers blades that probably were used as halberd) that is to say that only in these periods starts the production of real weapons (this is because the society in the Bronze age begins to be more and more complex). Also some stone objects called club heads (Neolithic age) seems to be some kind of prestige objects and of course the same is for the stone blades axe or adze (that are tools but could be used against a man).
Maybe it's too simplicistic but i think that the shape of yatagan, shashka and so on it's only another way to prevent that the sword slide from the hand. Also all the african weapons shows different shapes of the pommel, but functionly the idea is the same (think at the huge guradè-shotel pommel). And, at the end, also the cacatooa pommel in the kris prevent that the sword slide from hand.
As you say my two cents...
