I mean, we live in a current technological era where knowledge and intellect surmounts. I can see why emotions were important in the caveman era. Anger/jealousy/rage etc are all emotions that clearly backfire more often than not in the modern era, but for cavemen who's tribes were probably always trying to backstab and kill each other, being rash can be very useful. But at the same time, I can see how even today, some emotions can help the brain save energy. For example, logically reasoning why one must do a task is very computationally intensive, when on can just do it because they think it's fun.