Dough-boys in World War I and the Yanks in World War II did not travel without a sheath knife. Even in Vietnam, knives were designed to stab and slice. Custom made blades like a Randalls knife where prized. Some had adaptations such as a knob on the end of the hilt that could be used as a hammer. The first blades proably were used for domestic purposes such as scraping hair from a hide.
Many experts agree that it was women who invented knives to assist in food processing.
Many years later, hunters learned how to shape flint or chirt. During the Copper Age, they learned how to anneal and temper copper. At that time, knives became weapons. Today, things are changing. Knife manufacturers are working to provide more than just a defensive tool.