Arrange the sentences P, Q, R and S in the correct sequence to form a coherent paragraph.

P: Islam spread south past the Sahara very slowly, especially compared with its sweep across North Africa.

Q: Despite this fact, the traditional beliefs have not completely disappeared.

R: The spread of Islam overshadowed many indigenous (or native) religions, myths, and legends of sub-Saharan Africa.

S: Before the modern era, Africans south of the Sahara had relatively little contact with the rest of the world.