Prior to what Marx regarded as the start of the capitalist era in human history (i.e. before the 16th century), structural unemployment on a mass scale rarely existed, other than that caused by natural disasters and wars.[3] In ancient societies, all people who could work necessarily had to work, otherwise they would starve; and a slave or a serf by definition could not become "unemployed". There was normally very little possibility of "earning a crust" without working at all, and the usual attitude toward beggars and idlers was harsh.[4] Children began to work already at a very early age.