Mirror neurons is the way we acquire knowledge from the environment or others. We badly need to feel how others feel in each scenarios posed. So those who cry watching a movie are really intelligent since their mirror neurons works good. Of course, this only part of intelligence - the emotional side. Then you need to create the abstract lesson from the felt experience. Then you need to remember it. So mirror neurons + abstraction facility + memory makes a mature, empathic, intelligent being.
Abstraction and memory are there in animals however, mirror must be low in them. The mirror neurons gives us the shared experience and thus a society - superior form of intelligence. Thus we know what can make others better and when everybody does that everybody feels better - an implicit knowledge.