Yawning originates from multiple triggers.

1. Yawning originates from multiple triggers. It can be induced by higher brain carbon dioxide levels, territorial signal, body's need to stretch the lungs/throat, and simply by watching another yawn (caused by mirror neurons)
2. Mirror neurons are a group of neurons found in various parts of the brain that fire both if the animal performs an action or if the animal observes another animal performing that action.