A question important to this thread is what can and cannot be established as being fact. To go back to Descartes who really thought about this for a long time. His famous answer was "cogito ergo sum" I think therefore I am.
If you want to get down to the only thing you cannot deny as being true is the fact that you are a thinking being.
everything that your senses tell you could be a lie. The only thing that is absolutely true is the fact that one's own thoughts exist.
Descartes postulated as his worst case scenario the very cool concept of the 'evil genius' who is somehow feeding all false information into your senses (yes Virginia, the idea of the Matrix is from the seventeeth century) The only thing the evil genius cannot falsify is the fact that there is a thinking being that is experincing these thoughts.
As an aside, Descartes goes on to 'prove' using only what he can believe as being undeniably true (no external evidence, only thought), and using logic, the existence of a God.
one good website about Descartes is
u
http://www.utm.edu/research/iep/d/descarte.htm
What all I'm saying boils down to is that next to nothing in this world is absolutely provably 100% ipso facto true to a bazillion decimal points.
The question is how much certainty do you want to accept.
With that being said, evolution has been proven to the limit of certainty. Is it 100% undeniably true? No, nothing is, and scientist are aware of that fact, but its as close as you can get.