The use and invention of mortars and pestles seems related to the invention of quern-stones, using a similar principle of naturally indented, durable, hard stone bases and mallets of stone or wood to process food, clay, minerals or plant materials by crushing, pulverizing and grinding. The advantage of a mortar over a quern-stone is that the mortar is a deeper bowl containing the ground material without wasting and spilling it over the edges, like the material would be with flat grinding stones. Another advantage of mortars is that they can be made large enough for a person to stand upright next to them and use the combined strength of their entire upper body and gravity for better stamping. These large mortars also allow for several people with several pestles stamping the material in the same mortar faster and more efficient. Large mortars which a person can stand next to in an upright position are also physically easier to use and are more ergonomical by ensuring a better posture of the whole body than small querns, where a person has to crouch and use the uncomfortable, repetitive motion of hand grinding by sliding.