[gcb0]

you are talking about humans :)

probably they just had more food and resources on the new land so a distinctive traid on the tools that is status only could be aforded by most of the community.

imagine someone looking 500 years from now at us. They will see all the expensive cars in LA and bay area and wonder why those two societies needed such larger engined while all other societies had smaller ones. I'm surr they will inspect the remains of all those BMWs and find practical advantages over a fiat, but we all know it was chosen just for the looks and disposable income.

I bet it was the same with the spears.