Answer: The Catholic Church teaches that a Catholic may believe in the evolution of species as long as the evolutionary theory does not come in conflict with revealed religion, that is Catholic truth and teaching. Of course, a Catholic cannot possibly believe in any theory of evolution, which denied the world’s creation by the Supreme Being — God. Equally, a Catholic cannot possibly believe that man, soul as well as body, is descended from an ape, since we are taught expressly that a person’s soul comes from God directly into union with his body. A person must believe the inspired words of Genesis: “Then the Lord God formed man of dust from the ground, and breathed into his nostrils the breath of life; and man became a living being” (Gen. 2:7). What a Catholic must not doubt is that a person’s soul has never been in any process of evolution.
The First Vatican Council made sure that total evolutionism, which included an evolving god, was condemned as only a more subtle form of pantheism.
“The Magisterium[1] of the Church does not forbid that the theory of evolution concerning the origin of the human body as coming from pre-existent and living matter-for the Catholic faith obliges us to hold that human souls are immediately created by God-be investigated and discussed by experts as far as the present state of human science and sacred theology allow.
“However, this must be done in such a way that the arguments on both sides, those favorable and those unfavorable to evolution, be weighed and judged with the necessary gravity, moderation and discretion. And let all be prepared to submit to the judgment of the Church to whom Christ has given the mission of interpreting authentically the Sacred Scriptures and of safeguarding the dogmas of faith.
“On the other hand, those go too far and transgress this liberty of discussion who act as if the origin of the human body from preexisting and living matter were already fully demonstrated by the facts discovered up to now and by reasoning on them, and as if there were nothing in the sources of revelation which demands the greatest reserve and caution in this controversy” (Pius XII, encyclical Humani Generis (3896).
[1] Magisterium: The living, teaching office of the Church, whose task it is to give as authentic interpretation of the word of God, whether in its written form (Sacred Scripture), or in the form of Tradition. The Magisterium ensures the Church’s fidelity to the teaching of the Apostles in matters of faith and morals.