If memory serves, I think it originates from the gee-gee kung fu that war horses were taught back in medieval or Renaissance times.
[Edited to add]
It was -
"The Renaissance gave rise to a new and more enlightened approach to riding, as a part of the general cultivation of the classical arts. By the Victorian age, indoor riding had become a sophisticated art, with both rider and horse spending many years perfecting their form. Gueriniere, Eisenberg, Andrade and Marialva wrote treatises on technique and theory during these periods.
The horses were trained to perform a number of airs above the ground (or "sauts d'école") movements, which could enable their riders to escape if surrounded, or to fight more easily. These included movements such as levade, capriole, courbette, and ballotade. Movements still seen today in competitive dressage include the piaffe, passage, and half-pass."
Jul 26, 2012 - The London Olympics have swung a glaring spotlight onto dressage, with the entry of U.S. horse Rafalca into that genteel event. Rafalca is a 15-year-old Oldenberg mare. What makes her London debut so noisily newsworthy is that she is co-owned by Ann Romney, wife of Republican U.S. Presidential candidate Mitt Romney, who vocally opposes same-sex marriage. Rafalca and the Romneys will go up against an 11-year-old Netherlands gelding named Glock's Undercover. Though a newcomer to grand prix competition, Undercover will be ridden by one of the world's great dressage artists-- Dutch rider Edward Gal, who is openly gay.
[deep sarcasm]This horse dancing thing is just so athletic! Certainly compares with the track and field events, deffinately tops the cycling and swimming and is such a fine example of endurance. I bet all the rowers wish they were up to it! [/deep sarcasm]
Strikes me that it's a hang over from days of having to get patronage from "wealthy, landowning upper class snobby types" and putting on an event for their horsey interests. I have always been surprised that Fox hunting isn't an olympic sport.
Of course this is just my opinion based on my own prejudices and doesn't represent the views of the London 2012 Olympic Organising Committee, who can all enter the running jump for all care!
Horses for courses but it is something special when you are totally in synch with a horse, especially when its all going pear shaped around you, had one that was pretty tasty in an violent crowd, nothing to do with me. The next day he could do a school visit and have toddlers running around underneath him and having them stick their hands in his mouth feeding him mints
The Septics have basically the same thing but with a frightened bovine.
I think it's better, though the clothes are shite.