What would falsify evolution?

Simple - if they found the fossilised bones of humans in Mesozoic rock, or any rock older than the time that humans were supposed to have evolved. Evolution depends on stuff evolving in the right order - like you get mammals before humans and all that - so something drastically out of place would falsify it.

Hmmm... ok try this:"If a human fossil was found that was far older than the earliest dinosaur fossil, then that would falsify evolution."For "dinosaur", you could also say "earliest mammal fossil" or "therapod" or even "earliest fossilised tree" if you want to be extreme. Any of these would falsify evolution.