Early times were all on the job training. It would usually take an entire village to learn how to construct a shelter, when one moved one, he taught his skills to others. Hands on training.
On the job training is one of the earliest forms of training after the Observational training. On the job training is sometimes also known as Direct instruction. It cannot be identified exactly when and where it started because training has been done for workers in different ways for a lot of centuries. However we do know that this method is one of the earliest introduced in the history of job training.