Jinasena, is the first mention of varna and jati in Jain literature. Jinasena does not trace the origin of varna system to Rigveda or to Purusha, but to the Bharata legend. According to this legend, Bharata performed an "ahimsa-test" (test of non-violence), and during that test all those who refused to harm any living beings were called as the priestly varna in ancient India, and Bharata called them dvija, twice born. Jinasena states that those who are committed to the principle of non-harming and non-violence to all living beings are deva-Brahmaṇas, divine Brahmins. The Ādi purāṇa (9th c.) also discusses the relationship between varna and jati. According to Padmanabh Jaini, a professor of Indic studies, in Jainism and Buddhism, the Adi Purana text states "there is only one jati called manusyajati or the human caste, but divisions arise on account of their different professions". The caste of Kshatriya arose, according to Jainism texts, when Rishabha procured weapons to serve the society and assumed the powers of a king, while Vaishya and Shudra castes arose from different means of livelihood they specialised in. Medieval era, Islamic Sultanates and Mughal empire period (1000 to 1750) Early and mid 20th century Muslim historians, such as Hashimi in 1927 and Qureshi in 1962, proposed that "caste system was established before the arrival of Islam", and it and "a nomadic savage lifestyle" in the northwest Indian subcontinent were the primary cause why Sindhi non-Muslims "embraced Islam in flocks" when Arab Muslim armies invaded the region. According to this hypothesis, the mass conversions occurred from the lower caste Hindus and Mahayana Buddhists who had become "corroded from within by the infiltration of Hindu beliefs and practices". This theory is now widely believed to be baseless and false. Derryl MacLein, a professor of social history and Islamic studies, states that historical evidence does not support this theory; that whatever evidence is available suggests that Muslim institutions in north-west India legitimised and continued any inequalities that existed; and that neither Buddhists nor "lower caste" Hindus converted to Islam because they viewed Islam to lack a caste system. Conversions to Islam were rare, states MacLein, and conversions attested by historical evidence confirms that the few who did convert were Brahmin Hindus (theoretically, the upper caste). MacLein asserts that the caste and conversion theories about Indian society during the Islamic era are not based on historical evidence or verifiable sources,