> You are assuming...

I made no assumptions. As I pointed out to another commenter, you might be in too much of a haste to play at being a contrarian. It might be more useful to pay closer attention to what you're objecting to.

Evolutionary game theory demonstrates that evolution is a matter of fitness payoffs. If cost of a trait increases, fitness is reduced. The prevalence of a trait in a fit population is indicative that, at best, the trait increases fitness, at worst, it doesn't hinder it. In both cases, the genes tend to be passed on and the game is allowed to continue. When carrying the trait becomes costly, there's pressure to get rid of it (through the usual evolutionary means).

The above model encompasses all the unnecessary specificity you tried to bring into the matter. If you object to it, address your concerns to the scientists that are leading us all astray.

For now, let's circle right back to the author's original argument. Absence of an actually useful trait to increase fitness (i.e. protecting ones from certain food sources and others from predators) might be indicative of a hefty tax to pay for carrying it.