Have you seen men trying to move a fallen tree or some other heavy object? They will make sounds like ‘Heave! Ho!’ or ‘Yo! Yo!’ According 
to the ‘Yo Heave Ho’ theory, language arose from the noises made by people who were engaged in a joint effort to do something like lifting a rock or moving a tree trunk.The people who put forward this theory say that as people worked together in a group, their physical effort produced rhythmic grunts, which over time, became chants, and then language.
