The standard model for the entry of the Indo-European languages into India is that Indo-Aryan migrants went over the Hindu Kush, forming the Gandhara grave culture or Swat culture, in present-day Swat valley, into the headwaters of either the Indus or the Ganges (probably both). The Gandhara grave culture, which emerged c. 1600 BCE, and flourished from c. 1500 BCE to 500 BCE in Gandhara, modern-day Pakistan and Afghanistan, is thus the most likely locus of the earliest bearers of Rigvedic culture.