posted on Jul, 7 2010 @ 03:06 PM
Actually in some animals, like baboons yawning is seen as a dominating gesture, or a way of communicating your rank to the group.
Lions use it to show they are "ok" or "relaxed" with another lion.
Some scientists think it might be to get larger groups of humans, to rest simultaneously.
Long ago humans used to live in rather large groups.
And yawning might have been a signal to the group, to "relax" or "rest".
The theory of releasing toxins, seems strange to me.
Since all u do it tense up muscles and release your breath from your lounges.