The first traces of horses were seen in 30,000 BCE in the Paleolithic cave art. These were wild horses which were hunted for meat.
Then around 2000 BCE, they were used as a means of transport as chariot burials. The first evidence of domestication of horses was observed in the Eurasian steppes in approximately 3500 BCE.
The exact period of the domestication of horses depends on the definition of “domestication”.