al. (2006) and Sengupta et al. (2006), elaborated on Kivisild et al.'s (1999) suggestion that West Eurasian haplogroups "may have been spread by the early Neolithic migrations of proto-Dravidian farmers spreading from the eastern horn of the Fertile Crescent into India". They conclude that "the L1a lineage arrived from western Asia during the Neolithic period and perhaps was associated with the spread of the Dravidian language to India", indicating that "the Dravidian language originated outside India and may have been introduced by pastoralists coming from western Asia (Iran)." They further conclude that two subhalogroups originated with the Dravidian speaking peoples, and may have come to South India when the Dravidian language spread. Poznik et al. (2016) note that "striking expansions" occurred within R1a-Z93 at ~4,500–4,000 years ago, which "predates by a few centuries the collapse of the Indus Valley Civilisation". Mascarenhas et al. (2015) note that the expansion of Z93 from Transcaucasia into South Asia is compatible with "the archeological records of eastward expansion of West Asian populations in the 4th millennium BCE culminating in the so-called Kura-Araxes migrations in the post-Uruk IV period". Indo-European migrations Genetic impact of Indo-Aryan migrations , Wells et al. (2002) and argue for an influx of Indo-European migrants into the Indian subcontinent, but not necessarily an "invasion of any kind". notice that the correlation between caste-status and West Eurasian DNA may be explained by subsequent male immigration into the Indian subcontinent. argue that the Indian subcontinent was subjected to a series of Indo-European migrations about 1500 BCE. Metspalu et al. (2011) note that "any nonmarginal migration from Central Asia to South Asia should have also introduced readily apparent signals of East Asian ancestry into India" (although this presupposes the unproven assumption that East Asian ancestry was present – to a significant extent – in prehistorical Central Asia), which is not the case, and conclude that if there was a major migration of Eurasians into India, this happened before the rise of the Yamna culture. Based on Metspalu (2011), Lalji Singh, a co-author of Metspalu, concludes that "[t]here is no genetic evidence that Indo-Aryans invaded or migrated to India". Moorjani et al. (2013) notes that the period of 4,200–1,900 years BP was a time of dramatic changes in northern India, and coincides with the "likely first appearance of Indo-European languages and Vedic religion in the subcontinent". Moorjani further notes that there must have been multiple