For most gamblers, racing means horse racing .  What they put their money on is Equus caballus, of the perissodactyl family Equidae, an ungulate (or hoofed) mammal having a variation in the number of toes on its backgammon and front feet.  The first horses probably appeared in the Lower Eocene period, about 70,000,000 years ago, and were no bigger than small dogs.  Even when the world had moved on enough for man to appear, catch his horse, and domesticate it, the animal was still only 13 hands (52 inches) high. But after that there was rapid development until today the animal can range in size from the Shetland pony (about 36 inches high) to the massive Clydesdale (about 72 inches high).
Everything is older than you think, including horse racing.  The metropolitan Museum in New York has a statuette of an Egyptian race horse and jockey from 2000 b.c.;  the Hittites of Asia Minor recorded on their cuneiform tablets instructions for training race horses; and even earlier (about 3200 b.c.) there was some racing going on between Arab steeds that the Arabs had trained by tethering them, making them thirsty, and then freeing them to run to distant water.
One of the these Arab races had far reaching consequences for two tribes whose sheiks were steady rivals but who managed to keep the peace for a long time.  Both sheiks (like most rulers in the middle East at the time) owned studs of horses tens of thousands strong and both liked the spectacle of the thirsty animals speeding across the plain to the waterhole.  But lesser nobles on each side upset the status quo by matching selected horses from their masters’ studs against one another in a 12 mile race for a stake of 100 camels.  When the two best horses began drawing ahead of the rest, the onlookers surged onto the course and began hurling missiles at the other horses to speed them up.  This led to a free for all in which horses, tribesmen, and camels were all involved.  No poker winner was announced because the judges also joined the battle.  The fight led to a war that lasted for a century, and the two tribes virtually destroyed each other.
The Greeks (who had no horses until invading Arab and Persian cavalry brought them) turned the animals to sporting use almost immediately-first (about 2500 b.c.) in chariot races around a circular course a mile long; later, in the first horse races with riders, which were often combined with javelin throwing, torch bearing, or the pursuit of a ball in a development of the old Persian riding game, savlajan (polo).  The Romans held spectacular horse races in their circuses; in the Circus maximums, 380,000 people would sit daily and watch 50 horse races (with riders or chariots ) between sunrise and sunset, betting money, slaves, women, and reputations on favorite horses and riders.

Horses and riders flash by the camera at the climax of a race at Britain’s Ascot summer meeting.  Horse racing combines both speed and excitement, which  perhaps explains its unchallenged position as the world’s greatest gambling sport.

For the early Teutons and Scandinavians, horses were bred fro work and war.  Although thee exists (in the Morgan Library in New York) a printed poster advertising a horse race sponsored by the Duke of Würtemburg on December 21, 1511, Northern Europe showed little widespread interest in horse racing until the early 19th century, when some rich noble families built a course at Mecklenburg and imported stock from England.
In one form or another horse racing had been popular in Britain since the Roman invasion, when Arab horses (imported by the invaders) were matched in chariot races against Celtic ponies belonging to the Iceni and other tribes.  There are historical references to racing at Smithfield (now part of the City of London) in the 12th century, where the crusading Richard I offered “forty pounds of reedy gold” to the winner of a three-mile race.
Later monarchs (such as Henry VII Henry VIII, and Elizabeth I) were keenly interested in horse breeding and in hunting but did little to encourage racing.  But, in the early 17th century, James I made up for the relative indifference to the sport shown by his predecessors.  He built stables at New market, instituted the idea of a racecourse with a place for spectators, had a great deal to do with the founding of prizes for winning owners and jockeys, and even attempted to organize a horse race on ice when the River Ouse froze over in 1605.  Also, he began a royal interest in the sport that has continued in Britain to the present day.  Charles II rode his own horses in race meetings, and Queen Anne inaugurated the first Royal Ascot meeting in 1711.
The Mediterranean countries have produced great horses and horsemen from the earliest days.  Spain’s particular breed the Andalusian rivaled the Arab for endurance and grace.  In Italy a somewhat sturdier stock was raised, though there was a great deal of crossing with Arab and Spanish breeds.  In France, lines of splendid horses were bred from the days of the early Saracen invasions; but racing didn’t gain a popular following until 1681, when Louis XIV inaugurated a meeting at St. German and offered to buy the winning horse for its weight in gold.  (The offer was apparently turned down by the owner, an English aristocrat named Chevesey.) After the publicity attending this offer, the French nobility began establishing racing studs of their own, with great success.  A close liaison between the racing fraternities of Britain and France was also established, and the French never relaxed their interest in the sport until the Revolution.  Then ít  struck them that racing had been the sport of kings as well as of commoners, and they fanatically ordered the slaughter of every race horse in the country.  Napoleon re-established breeding to some extent (though naturally for his cavalry) but the Revolutionary destruction took many years to repair.  Today, however, France horses have won world famous sports events including the English Derbies of 1947, 1950, 1955, and 1963.

A first century A.D. horse and chariot in bronze.  The Romans were renowned for their sensational chariot races, which attracted enthusiastic crowds.  These circus races of classical times were the forerunners of the harness or trotting races that are popular today in Europe and North America.

There were no horses at all on the American continent until the Spanish expeditions at the end of the 15th century left some there specifically, five stallions and sevens mares of the Andalusian breed.  By 1700 these had become several thousands and had been crossed with imported Arabs to produce mustangs.  These were the horses with which racing was inaugurated on the American mainland at the end of the 17th century on the quarter-mile tracts in Virginia, though a race tract on Long Island had been laid out in 1665 and English horses had run there.  Canada, Africa, Australia, New Zealand, and India were (like America ) innocent of horses until colonizers or invaders took them there.  But once horses were imported, interest in racing them for money was eventually bound to arise.  India recorded her first race in 1791, South Africa in 1795, Australia in 1810, Canada in 1830, Canada in 1830, and New Zealand in 1837.