History of Bits
Humans and horses have intertwined throughout history, dating as far back as 2600 BC. Using historical evidence, it is believed that the first bits were made out of hemp rope, bones, horns or hardwood.
As the Bronze Age began, metal started to be used with horses and it triggered a new type of horsemanship. By 900 BC, horses became used for more than just for survival, but as a weapon. Most of the bits used in this time where simple straight bar mullen mouths and the horses didn’t have a ton of steering control. Around the 4th Century, the Celts invented the curb bit. This allowed leverage action allowed more control on the battlefield, and place for designs of crests and defense. Bits created in this era, were incredible barbaric by today's standards, but people only knew how to train horses with a large amount of pressure.
Things did start to change around 350BC, when one of the first renowned horseman, Xenophon wrote the book, The Art of Horsemanship. His writings are still taught today such as "If you desire to handle a good war-horse so as to make his action the more magnificent and striking, you must refrain from pulling at his mouth with the bit as well as from spurring and whipping him. [...] but if you teach your horse to go with a light hand on the bit, and yet to hold his head well up and to arch his neck, you will be making him do just what the animal himself glories and delights in".