National Geographic reports on a study of proboscis monkeys:
"Male proboscis monkeys with large noses tend to be bulkier than their small-nosed kin. They also sport bigger testes, up to 1.2 inches wide—upping their chances of fathering a female’s offspring by producing more sperm, crowding out less fertile males if they’re vying for the same female."
This study found that higher levels of umbilical cord testosterone predicted adult nose size in humans. Size matters -- nose size, that is.