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. According to Parpola, Indo-Aryan clans migrated into South Asia in subsequent waves. This explains the diversity of views found in the Rig Veda, and may also explain the existence of various Indo-Aryan cultural complexes in the later Vedic period, namely the Vedic culture centered on the Kuru Kingdom in the heartland of Aryavarta in the western Ganges plain, and the cultural complex of Greater Magadha at the eastern Ganges plain, which gave rise to Jainism and Buddhism. Writing in 1998, Parpola postulated a first wave of immigration from as early as 1900 BCE, corresponding to the Cemetery H culture and the Copper Hoard culture, c.q. Ochre Coloured Pottery culture, and an immigration to the Punjab . 1700–1400 BCE. In 2020, Parpola proposed an even earlier wave of proto-Indo-Iranian speaking people from the Sintashta culture into India at c. 1900 BCE, related to the Copper Hoard Culture, followed by a pre-Rig Vedic Indo-Aryan wave of migration: This pre-Rig-Vedic wave of migration by early Indo-Aryans is associated by Parpola with "the early (Ghalegay IV–V) phase of the Gandhāra Grave culture" and the Atharva Veda tradition, and related to the Petrovka culture. The Rig-Vedic wave followed several centuries later, "perhaps in the fourteenth century BCE", and is associated by Parpola with the Fedorovo culture. According to Kochhar there were three waves of Indo-Aryan immigration that occurred after the mature Harappan phase: the "Murghamu" (Bactria-Margiana culture) related people who entered Balochistan at Pirak, Mehrgarh south cemetery, and other places, and later merged with the post-urban Harappans during the late Harappans Jhukar phase (2000–1800 BCE); the Swat IV that co-founded the Harappan Cemetery H phase in Punjab (2000–1800 BCE); and the Rigvedic Indo-Aryans of Swat V that later absorbed the Cemetery H people and gave rise to the Painted Grey Ware culture (PGW) (to 1400 BCE). Gandhara grave culture and Ochre Coloured Pottery culture About 1800 BCE, there is a major cultural change