North Indians (ANI) which is "genetically close to Middle Easterners, Central Asians, and Europeans", and the Ancestral South Indians (ASI) which is clearly distinct from ANI. These two groups mixed in India between 4,200 and 1,900 years ago (2200 BCE – 100 CE), after which a shift to endogamy took place, possibly by the enforcement of "social values and norms" during the Gupta Empire. Moorjani et al. (2013) describe three scenarios regarding the bringing together of the two groups: migrations before the development of agriculture before 8,000–9,000 years before present (BP); migration of western Asian people together with the spread of agriculture, maybe up to 4,600 years BP; migrations of western Eurasians from 3,000 to 4,000 years BP. While Reich notes that the onset of admixture coincides with the arrival of Indo-European language, according to Moorjani et al. (2013) these groups were present "unmixed" in India before the Indo-Aryan migrations. Gallego Romero et al. (2011) propose that the ANI component came from Iran and the Middle East, less than 10,000 years ago, while according to Lazaridis et al. (2016) ANI is a mix of "early farmers of western Iran" and "people of the Bronze Age Eurasian steppe". Several studies also show traces of later influxes of maternal genetic material and of paternal genetic material related to ANI and possibly the Indo-Europeans. While others have analysed the herditary distribution of Lactose intolerance, and specifically the presence of the -13910T Lactase persistence mutation, found in Europe and Central Asia, across South Asia. Literary research: similarities, geography, and references to migration The oldest known inscribed Indo-Iranian words, and particularly invocations of the Indo-Aryan deities, date to mid second millennia BCE, as loan words in Hurrian treaties of the Mitanni kingdom, of present-day northern Syria. The religious practices depicted in the Rigveda and those depicted in the Avesta, the central religious text of Zoroastrianism, show similarities. Some of the references to the Sarasvati in the Rigveda refer to the Ghaggar-Hakra River, while the Afghan river Haraxvaiti/Harauvati Helmand is sometimes quoted as the locus of the early Rigvedic river. The Rigveda does not explicitly refer to an external homeland or to a migration, but later Vedic and Puranic texts do show the movement into the Gangetic plains. A number of Indologists and historians offering the Baudhayana Shrauta Sutra, verse 18.44:397.9, as explicit recorded evidence of a migration, while others have criticised their interpretations, or the