The established presence of Islam in the region that now constitutes modern Turkey dates back to the latter half of the 11th century, when the Seljuks started expanding into eastern Anatolia. According to religiosity polls, 97.8% of the population identifies as Muslim, but only 23% is really religious. Most Muslims in Turkey are Sunnis, forming about 72%, and Alevis of the Shia denomination form about 25% of the Muslim population.