Evolution is not a subject for belief.
Evolution is a scientifically established fact.
It is also accepted as to be a fact by various churches, including the Catholic church.
Theory of evolution is just a description of the evolutionary mechanisms and the ways they were discovered.
It is only not sure, are humans an effect of pure evolution or both evolution and accidental mutations which caused a rapid increase of brain size. Some scientists suspect that this rapid increase of brain capacity could have been caused by expostion to a natural source of radiation, such as natural uranium deposits.