Benjamin Franklin once quipped that nothing was certain but death and taxes. If Mr. Franklin were alive today, he would add evolution to the list of certainties. The theory has become fact and has won uncritical acceptance from nearly everyone, Catholic or not. Having become adamantine, this theory has broken Adam’s family into pieces with dire consequences both for the Faith and for the world because of one particular aspect, polygenism. Polygenism, put simply, is the belief that, rather than tracing our human origins back to a single couple, we came from multiple couples. Rather than look at each of the different theories in particular, we will examine the idea based through philosophical and theological lenses.
First it is worth mentioning that the Magisterium has cautioned the Faithful about accepting polygenism in any of its forms. In his 1950 Encyclical, Humani Generis, Pope Pius XII spoke of the liberty the Faithful have in discerning the origins of the human body. But,
“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”
Humani Generis, 36-37
It takes a bit of theological gymnastics not to read this as a blanket rejection of polygenism, but nevertheless some theological contortionists have posited that the door is still open. What is clear however is that any polygenetic theory would have to maintain two truths about Adam. First, that there are no men on earth that did not take their origin from him. Secondly, we cannot see Adam as somehow an icon or symbol for a bunch of first parents. Hard to imagine that any theory of polygenism could maintain this since it seems to assert its opposite, but even if the Pope did leave it open, there is no theory as of yet that meets this criteria.
Pius XII mentions the theological interest in the question as it relates to Original Sin. It leaves open the possibility and historical reality of an unfallen race at various time points throughout history. Even if all mankind eventually fell, there would have been a time when unfallen and fallen men lived together. That means there may have been unfallen men who were conceived of unfallen parents. This would then call into question the dogma of the Immaculate Conception by which Our Lady is said to have received a “singular grace”. It also leaves open the possibility that men died without falling and thus would not be in need of redemption. If all men did not sin in Adam then all men are not redeemed in Christ.
This is not the only way that polygenism tugs at the thread of the seamless garment of the Faith in ways we do not initially grasp. It also puts in jeopardy the dogmatic truth of the special creation of Eve. It is a matter of dogma taught through the Ordinary Magisterium, and first affirmed Pope Pelagius I in 561 and reaffirmed by Pope Pius XII in the aforementioned Encyclical that Eve was literally created from the rib of Adam. This belief is protective of the equal dignity of men and women because they come from the same origin.
It turns out that polygenism not only leads to inequality between the sexes but between races as well. The evolutionary model rests upon a progressive view of beings. Things are always adapting and getting better. From a philosophical perspective, evolution is the tool by which the rungs of the Ladder of Being are being added. Beings on the same rung are equal in dignity, those above or below have more or less dignity. Human beings are equal in dignity because they occupy the same rung of the Ladder of Being. Under the model of polygenism this ceases to be the case. With different evolutionary origins, different races occupy different rungs on the ladder. In short, it gives both biological and philosophical justification for some human persons being more equal than others.
This is why the Francis Galtons, Margaret Sangers and Hitlers of the world have always loved the Theory of Evolution. It justified their eugenic madness. Under polygenism, some races would necessarily be inferior to other races. This would justify their extermination and there would be no disputing them. This is why Pope Pius XII thought it necessary to safeguard not just Revelation, but man’s unique place within visible creation against the threat of uncritical acceptance of Evolution. Ideas have consequences and all of us, especially Catholics, need to be more critical in their acceptance of the Theory of Evolution.
Before closing, it is worth mentioning that many well-meaning Catholics accept polygenism because it seems better than accepting incest among Adam and Eve’s children. Rather than revisiting that question here, I will simply point you to a previous post that deals with that objection.