The question below consists of a set of labelled sentences. Out of four options given, select the most logical order of the sentences which forms a coherent paragraph.

We know that dogs are a human's best friend.

P. They love us and we love them.

Q. Although wolves are wild and dogs are tame, they're still a lot alike.

R. Many scientists think they came from wolves 15,000 years ago.

S. Both wag their tails when happy and put their tails between their legs when scared.

These similarities today depict the relationship which they built with humans over 15,000 years ago.