Why is the outer nose shaped as it is? Why don't humans just have two holes in the face, rather than this protuberance that we care so much to have the right shape of?
Here's the best illustration I've seen of my pet hypothesis:
Imagine that little baby had two holes rather than a nose. It would suffocate. That huge breast would block the air intake, making it impossible to breastfeed. But when the baby's nose is pushed from the front, slits are formed that enable the baby to still breathe through the nose.
In other words, humans have a proboscis so that they can breastfeed.
Some support: Cows, dogs, and cats have a slit to the side, making them able to breathe when their noses are blocked form the front.
A caveat: Snub-nosed monkeys have no external nose, but just two holes. Admittedly, they probably breastfeed. I wonder how they do it. They also sit with their faces downwards when it rains, to prevent rain from entering their nostrils. I wonder if the olfactory abilities of these monkeys are reduced?
More on the variation of nose shapes in humans and the evolutionary origin of the human nose, but nowhere can I find anyone suggesting a link between nose-shape and breastfeeding.