Some Catholic thinkers argue that the doctrine of Original Sin and the theory of the evolution of the human body are incompatible. Consider, for example, this article from Remnant, written by Peter Wilders:
“Indeed, how can there have been a first man Adam who committed the original sin of pride in collusion with the first woman Eve, if he had ancestors going back into the mists of time? How can Adam, the perfect creation of God, have been a grunting Neanderthal or other such hominid species? If he were, the Church has lied and its dogmas have no application to Catholic teaching. Yet, the “credo” of today’s science is that there was a gradual development from a hydrogen particle to man. The notion of a single man created ex nihilo is not envisaged.[…]
Let it be clear. All speculation on Adam having had ancestors, in any form whatsoever, negates the teaching Magisterium of the Church.”
Let us examine these claims.
The doctrine of Original Sin holds that the first man, Adam, sinned through disobedience to God’s commandment. The consequences of that sin, namely a lack of sanctifying grace, are transmitted to Adam’s posterity. Note that the action which constituted the Original Sin took place after Adam’s creation as the very first human being. So what we have here are two separate events: first, the creation of the first man, and later man’s fall.
Now, the theory of evolution holds with respect to man’s body that it was developed from a pre-existing animal body. Don’t forget that Catholic doctrine holds that man’s soul can only be created immediately by God; we cannot endorse any view which holds that man in his entirety (body and soul) is derived entirely from natural causes. However, we can hold that God created man’s body using a pre-existing animal body through some evolutionary process. Note Pope Pius XII’s Humani Generis:
“…[T]he Teaching Authority of the Church does not forbid that, in conformity with the present state of human sciences and sacred theology, research and discussions, on the part of men experienced in both fields, take place with regard to the doctrine of evolution, in as far as it inquires into the origin of the human body as coming from pre-existent and living matter – for the Catholic faith obliges us to hold that souls are immediately created by God.”
Thus Catholics may hold the possibility that the human body was developed through some process of evolution, but Catholics must also maintain that the human soul is directly the creation of God.
Mr. Wilders seems to think that bodily ancestors to Adam would have to be some sort of sinless primitive humans. Orthodox Catholic advocates of evolution do not, and in fact cannot, claim this. The ancestors of Adam could not have been human, otherwise they would not have been ancestors of the first man, they would have been men themselves. The first man, whatever means God used to create him, was quite distinctly the first man. Any ancestors, if they existed, who contributed to the formation of his body were quite distinctly not men, but animals. There is and must be in Catholic teaching a clear demarcation between man and not-man.
Once you do have the first man, however, you have Adam, and Adam may sin. The doctrine of Original Sin applies to the first man and his descendents. It is irrelevant to his non-human bodily ancestors. Their existence has no bearing on his free choices as a man or the effects of those choices on his fully human ancestors.
Let’s also take a look at how Humani Generis treats the issue. Crucially, HG explicitly discusses the question of the compatibility of Original Sin and evolution. HG quite pointedly does not forbid investigation into the hypothesis of the development of man’s body via evolution. It does forbid a specific version of evolutionary theory, namely polygenesis, because that theory, in the words of HG, is not apparently reconcilable with the doctrine of Original Sin:
“When, however, there is question of another conjectural opinion, namely polygenism, the children of the Church by no means enjoy such liberty. For the faithful cannot embrace that opinion which maintains that either after Adam there existed on this earth true men who did not take their origin through natural generation from him as from the first parent of all, or that Adam represents a certain number of first parents. Now it is in no way apparent how such an opinion can be reconciled with that which the sources of revealed truth and the documents of the Teaching Authority of the Church propose with regard to original sin, which proceeds from a sin actually committed by an individual Adam and which, through generation, is passed on to all and is in everyone as his own.”
Thus, in one and the same document, the Church teaches that the doctrine of Original Sin is incompatible with one specific form of evolutionary theory, but also explicitly allows the general idea of human evolution without any other concerns about compatibility with Original Sin.
So, the pertinent magisterial document allows for the general compatibility of Original Sin and the evolution of the human body. Reason as well demonstrates their compatibility: evolution applies to some aspects of how man’s body was formed; Original Sin applies after the first man is in existence and disobeys God, regardless of the details of his coming-into-existence. They apply to two separate points.