By the time H. erectus came along, the orientation of the shoulder the torso, the twist to the humerus, the tendons and ligaments to store energy, and the waist mobility that lets us throw from the hips were all there. Our fastballs have just been getting better ever since.
Humans are the only primates that can throw the way we do.
Sure, our chimpanzee and gorilla kin are much stronger, but they throw like wimps. Only H. sapiens throws hard enough to kill.
In fact, the fastest motion generated by the human body is the rotation of the humerus during a hard throw.
Our projectile-oriented nature is thought by some to be a reason hunter-gatherer societies tend to be more egalitarian, less hierarchal, than either the typical primate troop or later, settled agricultural or urban ones. If one or two dudes in a hunter-gatherer tribe got too big for their britches, it was too easy for the rest of the group to stand off at a distance and pelt him with rocks...or spears, or arrows.
"Boehm has discovered that, among the tribal and hunter-gatherer human societies he studies, the development of projectile weapons is a key step in the growth and maintenance of equality: it puts the strong at greater risk from the weak. Such weaponry is one reason that human societies are more equalized than those of other primates.I first ran across the ideas Boehm is talking about in the Peter Turchin book, Ultrasociety: How 10,000 Years of War Made Humans the Greatest Cooperators on Earth. If you haven't read it, I highly recommend doing so.
But weapons aren’t enough to make equality last. Boehm finds that, to really maintain the new social order, the dominated need to trust one another. They must have stable social bonds and anticipate a long future together. Most important, they must be able to communicate effectively."
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