Justin Bieber may be only sixteen, but the teen sensation is growing up fast ... talking about politics, puberty and sex in Rolling Stone's March issue. Look at that adorably cute mug trying to look hard. The spikes on the shoulder definitely complete the hardcore look.

Biebs, who has been dating 18-year-old actress and singer Selena Gomez, is opening up about his love life. He tells the mag:

    "I don't think you should have sex with anyone unless you love them. I think you should just wait for the person you're...in love with."

When asked about his political views, the singer adds:

    "I'm not sure about the parties. But whatever they have in Korea, that's bad. I really don't believe in abortion. It's like killing a baby?"

Gotta love that this 16-year-old kid is already cruising around Atlanta in a Range Rover and taking on the tough questions. You go, boy!

See behind-the-scenes of Bieber's Rolling Stone photo shoot with Terry Richardson ... after the jump.