[FuzzyUK (OP)]

Why does our nose point downwards whereas most animals noses point forward?

[CliffordK]

I don't think there is any definitive answer. 

There is one theory called the Aquatic Ape Hypothesis in which the ability to be good swimmers was important to the history of human evolution, and that the "hooded nose" as well as some other features were adaptations for swimming.

Perhaps one difference between humans and many other animals is our high reliance on vision, and perhaps also good hearing frequencies and localization, and less of a reliance on smells. 

A forward facing nose would allow better localization of smells.  Our downward facing nose would be awkward in many situations.  However, with the upright stance, it is also difficult to bend down to smell a blade of grass like a hound dog might do. 

So, with that in mind, our posture separating the nose from the ground, it is less important to have the nose in a direction to smell the ground.  A downward facing nose would tend to protect it better from rain and moisture, and would also point it towards our mouth where we are eating food.

Here's an interesting thought.  I'm seeing various notes about dog domestication being around 10,000 to 30,000 years ago, but some as long as 100,000 years ago.  Is it possible that canine domestication has affected the human sense of smell?  If the domestication of dogs was as early as 100,000 years ago, it would have put it in line with the separation of homo sapiens from other hominid species, although likely late in the 5+ million year hominid evolution.

[Bored chemist]

I'm sure this used to be an old joke.
"Why isn't your nose the other way up?
If it was you would drown when it rained."
Silly, but not without merit.