There are 49 established Hindu gotras. All members of a particular gotra are believed to possess certain common characteristics by way of nature or profession. Many theories have been propounded to explain this system. According to the brahminical theory, the Brahmins are the direct descendants of seven or eight sages who are believed to be the mind-born sons of Brahma. They are Gautama, Bharadvaja, Vishvamitra, Jamadagni, Vashista, Kashyapa and Atri. To this list, Agasthya is also sometimes added.