Evolution is a wierd thing. There are a few conditions before and evolution can take place. First of all there needs to be a kind of mutation, which needs to be able to pass to next generations. Second of all it musn't die out, so it needs some luck and must be a benifit in the situation or enviroment the mutated creature is. Third the evolution can only be complete if the whole species evolve or if a isolated (or soemthing similar) group evolves next to the original species, or the others without the advantage must die out (if this happens quickly an evolution can take place rather rapidly.

Now Evolution doesn't need to be that slow. Recently a type of bird evolved in only 30 years. It's nozzle (is that the word?) became significantly smaller in that period as it got new competition of another bird, which ate the same food. Now the bird has changed it's diet and it's nozzle to survive:
http://news.nationalgeographic.com/n...evolution.html

Anyway some other very interesting articles from National Geographic news:
http://news.nationalgeographic.com/n...evolution.html
http://news.nationalgeographic.com/n...evolution.html