Certainly my examples weren't what happened exactly, those were just general pictures to visualize the principle I was talking about. To turn it around, we lost our ability to climb trees properly (look at our feet), and I'm pretty sure it's because we didn't need it anymore, and not because a random mutation forced us to live on the ground.
And your mane example makes me wonder if you got my entire point. I was never talking about cognitive functions influencing the genetic make up (the “i want a mane so hard“ thing). That is very certainly not the way it works.