Unbound: How Eight Technologies Made Us Human and Brought Our World to the Brink

by Richard L. Currier

The ability to carry and wield a spear long enough to attack and kill another animal from beyond the range of its biological weaponry would have had powerful survival value. Once the ancestors of the hominids had adopted the technology of the spear, those individuals who could stand firmly on their hind limbs—while jabbing and thrusting a spear with their forelimbs—would have had a clear advantage over their competitors. The longer these individuals could remain standing, the farther they could walk and run on two legs, and the larger and heavier weapons they could carry with them, the more effectively they could defend their mates and offspring against attacks from would-be predators—and the more meat they could bring back to share with the other members of the group. For all of these reasons, the survival value of fabricated spears would have been sufficient to bring about the major anatomical changes required for a four-footed animal to evolve into a two-footed animal.