There is an element of "personal incredulity" when one first is told that "we evolved from apes". One naturally reacts negatively to that thought.
It is counter to EVERYTHING that one accepted as truth up to that moment.
And it is only human nature (hmm - where did human nature come from? but I digress) to immediately defend the "true" truth and make up all kinds of reasons why we couldn't have evolved from apes. I'll admit, it is hard to imagine. But personal Incredulity disapates when you begin to understand all the scientific evidence that underlies evolution theory.
You'll see the evidence a bit later in the presentation.