We know that you can only get avian flu from getting in...

We know that you can only get avian flu from getting in contact with a chicken or a bird species with it. That's bad enough. We don't transfer it from one human to another, which is really bad! But from the infective agent's point of view, the virus' point of view, its going to say 'to be more adaptive, maybe I'll switch hosts, and I'll adapt to a system where humans are transferring to each other.' We wouldn't even have a concept of that or a worry of that without Darwin's theory of evolution.