Chopsticks used to be used mainly for cooking by their capability to reach deep into boiling pots. Eating utensils were common around 400 AD, but that was also when there was a population boom and resource tension forced cooks to develop ways to cook food and save fuel. One useful way to do this was to cut up whatever they were cooking into small pieces so they can cook faster. Utensils like forks and spoons became more troublesome to eat with and led to people using chopsticks for their tweezer-like grip.