The Theory of Evolution is not something to hate, nor something to love. It is just an observation that:
1) Genetic characteristics get propagated from parent to offspring, and
2) Characteristics that improve the survival of descendents are more likely to be propagated than characteristics that impede survival.
Take the example of the peacock, that the professor was starting to get into when the woman flipped out. On the surface, having a large gaudy tail would not seem to be an asset for survival. It takes bodily energy to grow it, it's heavy, cumbersome, and a general handicap to survival. Yet female peacocks select for it in males.
The fact that it's a handicap to the males is precisely WHY females select for it.
Male peacocks to not participate in the raising of their offspring. They just contribute sperm. It's not important how many survive, as long as at least one does per area. But BECAUSE that silly tail is such a handicap, the ones who do survive are the ones with superior strength, energy, and resistance to parasites. These characteristics get passed on to female as well as male offspring. And the whole point of the game is to produce as many superior female offspring which survive to have their own chicks.
Therefore there is no good way for a male to “cheat” by producing lots of testosterone to, for example, grow a magnificent rack of antlers - without an equal and opposite hit on the immune system.
So if a female deer sees those amazing antlers - but the buck looks diseased and sickly - she will take a pass. But if the buck has amazing antlers denoting high testosterone production - AND he has a healthy coat and looks fit as a fiddle - she is going to go for that!
He demonstrated that he had a very healthy immune system - while he was growing an impressive rack of antlers - fueled by testosterone production.