The Bene Israel narrative appears to be based on the ten lost tribes of Israel that escaped persecution by Greek monarch Antiochus Epiphanes in 175 BCE. They were stranded on the Navigation shoreline, which is today home to an ancient Bene Israel cemetery. They are India’s oldest and largest Jewish community. Despite the loss of their holy texts when they arrived in India, they persevered and continued to keep the sabbath, keep kashrut, celebrate the major festivals, circumcise their boys, and hold steadfast to the vestiges of Jewish observance in faintly remembered forms for untold decades.
The Bene Israelis became fluent in Marathi and accepted local customs. They began pressing oil and absorbed it into local culture, eventually resembling the Marathas in appearance and traditions. Teachers from Baghdad and Cochin did not teach them mainstream Judaism until the eighteenth and nineteenth centuries. They were finally able to read the Torah and build on their Jewish culture and traditions at that time.
Source: http://www.jewswerehere.com/asia/southasia/india/bene-israel/