Many of these ulema also believed that it is best to marry within one own caste. The practice of endogamous marriage in one's caste is strictly observed in India.[38][39] In two of the three genetic studies referenced here, in which is described that samples were taken from several regions of India's Muslim communities, it was again found that the Muslim population was overwhelmingly similar to the local non-Muslims associated, with some having minor but still detectable levels of gene flow from outside, primarily from Iran and Central Asia, rather than directly from the Arabian peninsula.[31]