It's absolutely astonishing that I've lived all these years in total ignorance of onagers. And would have presisted in abysmal onagerian oblivion hadn't read David Anthony's fascinating monograph, The Horse, the Wheel, and Language (2007). Anthony's thesis is that "proto-Indo-European" -- from which the Slavic, Celtic, Germanic, Romance, and Indic languages, among others, are descended, originated in the steppes north of the Black and Caspian seas. The inhabitants of these areas domesticated horses and invented or adopted the wheel and the wagon, which gave them the technological advantage to spread their culture and language across the steppes eastward as far as China and westward to the Atlantic. This same people also invented the chariot -- a horse-drawn single-axle vehicle, which, manned by a warrior armed with bronze-headed javelins, was the principal engine of war for the thousand years that began about 1700 BCE and ended about 700 BCE. It's a lovely hypothesis, bristling with the evidence of hundreds of archeological digs.
Pre-proto-Indo-European speakers ate horses long before they domesticated them and rode them before they learned to harness them to chariots and wagons. However, horses weren't the only equid in the neighborhood. There were also onagers.
But all they could do with onagers was feast on them. The evidence lies in the thousands of midden heaps that are loaded with onager bones. Here are two onagers:
Onagers are half the size, or less, than the horses with which we are familiar. They are apparently untamable, like zebras, but, uniike zebras, edible. (So tasty, in fact, that fewer than a thousand of them survive in the wild.)
Anthony doesn't say so, but if there had been only onagers, and not those noble and cooperative horses, we would certainly not be speaking and writing an Indo-European language -- and, for that matter, we might still be trundling across the wide Missouri in oxcarts.
From the Bronze Age down to the second decade of the nineteenth century, the horse was the fastest and most reliable way to travel, the quickest way to convey information, the backbone of armies, and the most conspicuous index of wealth and status.
Horses are handsome and intelligent. Onagers are ugly, awkward, and stubborn, and could never have taken part in the creation of complex civilizations. Poets have celebrated "fiery Pegasus" for millenia; no one, to the best of my knowledge, has ever rhapsodized the onager.