According to the widely accepted Kurgan hypothesis, the Indo-European language and culture spread in several stages from the Proto-Indo-European Eurasian homeland in the Pontic steppes, into Western Europe, Central and South Asia. This process started with the introduction of cattle at the Eurasian steppes around 5200 BCE, which led to a new kind of culture. Between 4500 and 2000 BCE, this "horizon", which includes several distinctive cultures, spread out over the Pontic steppes, and outside into Europe and Asia.