The invention of the wheel used in transportation most likely took place in the Eurasian Steppes of modern-day Russia and Ukraine. Evidence of wheeled vehicles appears from the mid 4th millennium BC near-simultaneously in the Northern Caucasus (Maykop culture), and in Central Europe. These earliest depicted vehicles may have been ox carts. A necessary precursor to the invention of the chariot is the domestication of animals, specifically horses – a major step in the development of civilization. Despite the large impact horse domestication has had in transport and communication, tracing its origins has been challenging. Evidence supports horses having been domesticated in the Eurasian Steppes, with studies suggesting the Botai culture in modern day Kazakhstan being the first, about 3500 BC.