Do you believe in behavioural modernity?

[Angrboda]

Contrast if you would the bolded portion of your post with the bolded portions of the web site. These javelins were not fashioned by some grunting ape. There is an obvious understanding of aerodynamics - even if they did not understand it as such.

I think your inference is a bit broad. It is possible for technology to evolve to a point of refinement through a process of cultural evolution, wherein with each generation, those with the best spears have the greatest influence on the succeeding generation. So while it's plausible that they possessed considerable knowledge and intelligence, it isn't necessarily the case when dealing with a simple technology. This is not my field, but if I'm not mistaken, many times the procedures for creating technological items become highly ritualized, even including superstitious elements which do not affect the utility of the item. So cultural evolution of such items without any understanding of the principles of their operation is also plausible.

(There are many examples of this in even the modern era, where technological items evolved through a series of stepwise refinement and competition, without any actual grasp of the underlying reasons for the change in the utility of the item. For example, the fluid dynamics associated with boats and sailing vessels.)