Why must Jonas take pills?

According to community rules, Jonas must take a pill to stop “the stirrings,” or the onset of sexual desire during puberty. Jonas’s mother gives him the pills after he talks about an erotic dream in which he wanted to bathe Fiona, which reveals Jonas’s burgeoning sexuality. Since the community controls childbirth and marriage, the elders most likely curb the citizens’ sexual desires to avoid people having children outside of the system or choosing their own partner.