about the missing links...
species that are not flexible enough for changes in the environment or species that have too much competition eventually die out. that is what happened to the neanderthals for instance.
most species are vastly inferior to us in terms of mental capacity...nevertheless they are very successful. thats because they are perfectly adapted to the environment they live in and they have not too much of competition for the ecological niche they live in.
the neanderthals died out for probably 2 reasons....firstly because of the last ice age...they couldn'T adapt well enough...secondly because of competition from the homo sapiens.
that the missing links had higher mental powers than the ape linage didn't mean necessarily that they had superior tactics to survive (number of offspring per female, possible food sources, etc.).
think about it ...after your logic all more primitive species would have died out millions of years ago.
I'll take your word for it that the universe isn't as complex as it seems.
the universe is very complex....but you can reduce the complexity to only three or maybe even just one single physical law. all the movements, objects (be it nebulas, stars, planets, galaxies, chemicals, animals) and effects can be explained with it.