I am not personally Shintoist, however as I am deeply concerned in Japanese culture, I believe I can explain.
Beliefs: In Shinto, there are "Kami"s. These are, in basic words, natural forces. The most significant one is Amaterasu(Sun-Kami) whose son is the Japanese emperor.
Rituals: In Jinjas(Shinto temples), people can marry or worship the Kamis. In some occasions, like the New Year, they decorate their homes so that bad spirits are avoided.
Scriptures: Nihon-gi and Kojiki
Evolution Theory: It is up to the person.
Afterlife: If you are a great warrior or something, then you will be honoured by many many people in Japan after you die. If you are just a normal person, you will be helping to your future generations.
Where does all of this evil come from?: If you have a bad relative who is deceased, he may be causing all of this trouble. Or regardless of that, if you make a Kami angry, it will cause really bad things on you. If you don't honour them enough or cause anything which can break the balance, there will be consequences.