"The fabled ruins of Yin, in Henan province, provided not only the earliest examples of Chinese writing but also the first known chopsticks—bronze sets found in tombs at the site. Capable of reaching deep into boiling pots of water or oil, early chopsticks were used mainly for cooking. It wasn’t until A.D. 400 that people began eating with the utensils. This happened when a population boom across China sapped resources and forced cooks to develop cost-saving habits. They began chopping food into smaller pieces that required less cooking fuel—and happened to be perfect for the tweezers-like grip of chopsticks.
As food became bite-sized, knives became more or less obsolete. Their decline—and chopsticks’ ascent—also came courtesy of Confucius. As a vegetarian, he believed that sharp utensils at the dinner table would remind eaters of the slaughterhouse. He also thought that knives’ sharp points evoked violence and warfare, killing the happy, contended mood that should reign during meals. Thanks in part to his teachings, chopstick use quickly became widespread throughout Asia."
And this, which is slightly different.
en.wikipedia.org