Complex sentence: In the 13th century the Beja accepted Islam as the Bedouin tribes spread into Sudan and swamped the Nubian kingdoms, so as of 2007 the majority of Beja are believed to be muslim.
Split into simpler sentences: In the 13th century, the Beja accepted Islam as the Bedouin tribes spread into Sudan and swamped the Nubian kingdoms. As of 2007, the majority of Beja are believed to be Muslim.