Here's a breakdown of the evidence supporting this theory:
* Linguistic evidence: The Indo-European languages share a common ancestor, known as Proto-Indo-European. This language is believed to have been spoken in the Pontic-Caspian Steppe around 4500-3000 BCE.
* Archaeological evidence: Archaeological findings in the region, such as the Kurgan culture, suggest a society with a strong equestrian tradition and a highly mobile lifestyle, consistent with the lifestyle of the early Indo-European speakers.
* Genetic evidence: Studies of ancient DNA have found genetic links between people from the Pontic-Caspian Steppe and various Indo-European groups in Europe and Asia.
However, other theories exist, including:
* Anatolian hypothesis: Some scholars propose that Proto-Indo-European originated in Anatolia (modern-day Turkey) and spread from there.
* Out-of-India hypothesis: This theory suggests that Indo-European originated in India and spread outwards.
The evidence for these alternative theories is weaker than for the Pontic-Caspian Steppe hypothesis, which remains the dominant theory among linguists and archaeologists.
Important note: This is a complex topic with ongoing research and debate. The evidence is constantly being reevaluated and new theories are emerging.
For further exploration:
* The Horse, the Wheel, and Language: How Bronze-Age Riders from the Steppes Shaped the Modern World by David W. Anthony
* The Indo-European Languages by R.S.P. Beekes
* The Kurgan Culture and the Indo-European Expansion by Mallory, J.P. and Adams, D.Q.