How Is Original Sin Passed On, and Can It Fit With Evolution?

Two Hard Questions

The basic teaching on original sin is clear. Through the sin of our first parents, humanity lost the holiness and justice God had given it, and every human being is born deprived of that original grace and wounded in nature (CCC 396–409). (For the plain explanation, see What Is Original Sin, and Why Does It Affect Us?)

Two questions follow that the basic explanation does not answer.

The first is moral. How can anyone inherit a sin? Guilt seems to be personal. I am not guilty of my great-grandfather’s crimes.

The second is scientific. Modern biology tells us that human beings emerged through a long evolutionary process, and genetics suggests that the human population never passed through a bottleneck of just two individuals. How does this fit with a first couple and a first sin?

Sin “Contracted, Not Committed”

The Church answers the first question with a precise phrase. Original sin is “contracted” and not “committed” (CCC 404). It is a state, not an act.

The Catechism explains that original sin is called “sin” only in an analogical sense. It does not carry personal guilt in the way our own sins do. It is the privation of original holiness and justice: the absence of the grace that God intended human nature to have (CCC 405).

An illustration: imagine a family that loses a great inheritance through the father’s reckless choice. His children are born poor. They are not guilty of his recklessness, but they genuinely lack what they should have had. Original sin is like that, except that what was lost is not money but friendship with God.

This is why St Thomas Aquinas, following St Anselm, defined original sin above all as the lack of original justice (Summa Theologiae I–II, q. 82). The wounds that follow (ignorance, weakness of will, disordered desire) are consequences of that loss.

Passed On “by Propagation, Not Imitation”

The Council of Trent, in 1546, taught that original sin is transmitted “by propagation, not by imitation.” This phrase was aimed at the Pelagians, who in the fifth century held that Adam’s sin harms us only by bad example: we copy him.

The Church rejected this. If original sin were only imitation, a child raised among saints might escape it, and Christ would be merely a good example to counter a bad one. Instead, the Church teaches that original sin belongs to human nature as it is now handed on, so that every human being needs Christ as Saviour, not just as model. This is why the Church baptises infants (CCC 403).

But the soul is not inherited

This raises a puzzle. The Church teaches that each human soul is created directly by God, not passed on by the parents (CCC 366). If the soul comes fresh from God, how can it be stained?

The usual answer is that original sin is not a positive stain injected into the soul. It is an absence. God creates each soul and unites it to a body descended from Adam, and in doing so He does not give the gift of original justice that was forfeited for the whole human family. The soul comes into being as part of a human nature that has lost that inheritance.

The Catechism admits frankly that the transmission of original sin “is a mystery that we cannot fully understand” (CCC 404). We know that it is so, without fully knowing how.

The Fall and Evolution

Now to the second question.

What the Church allows

The Church has not opposed the scientific study of evolution. In the encyclical Humani Generis (1950), Pope Pius XII allowed Catholics to investigate the evolution of the human body from earlier living matter, provided they held that the soul is created immediately by God (Humani Generis 36). St John Paul II, in 1996, said that new knowledge had led to recognising evolution as “more than a hypothesis.”

The Catechism also recognises that the account of the Fall in Genesis 3 “uses figurative language.” But it insists that it affirms “a primeval event, a deed that took place at the beginning of the history of man” (CCC 390). The Fall is not simply a symbol of the human condition. Something actually happened.

The real difficulty

The sharper question concerns the first parents. Humani Generis addressed the idea of polygenism, the view that the human race descends from many first parents rather than one couple. Pius XII wrote that Catholics cannot embrace it, because “it is in no way apparent” how it could be reconciled with the Church’s teaching on original sin as a sin committed by one Adam and passed on to all (Humani Generis 37).

Notice the careful wording. Pius XII did not say that polygenism had been proved incompatible. He said it was not apparent how it could be reconciled. That leaves room for theologians to look for a reconciliation.

How theologians approach it

Several approaches have been proposed by theologians faithful to the Church. None has been officially adopted, and they should be seen as attempts, not settled answers.

Theological monogenism. One approach distinguishes biological populations from theological humanity. The genetic evidence concerns a population of hominids. But the first true human beings, in the theological sense, were those to whom God first gave a spiritual, rational soul. On this view, God may have given rational souls first to a single pair, Adam and Eve, within a larger population. Their descendants, who received rational souls, would all be their descendants in the line that matters, even if interbreeding with the wider population occurred. All human beings would then descend from that first couple, and all would inherit the consequences of their sin.

A first human community. Others suggest that the first sin may have been committed by a first human group, with the singular “Adam” representing that group. Theologians who take this view must explain how it honours the Church’s teaching that original sin is passed on to all by descent, not imitation. This is a live area of discussion, and the Church has not endorsed it.

What every Catholic approach must keep is this: there was a real beginning to human history; human beings were created in grace; that grace was lost by a free sin at the origin of our history; and every human being is affected by that loss and needs redemption in Christ.

Why It Still Matters

Original sin may seem an abstract doctrine, but the Catholic writer G. K. Chesterton called it the only part of Christian theology that can be proved: one only has to look at the world.

It explains why good people do bad things, why every human society is marked by injustice, and why moral improvement through education or politics alone never fully succeeds. It also explains why we need a Saviour and not merely a teacher.

Above all, original sin is the dark background against which the Gospel shines. “Where sin increased, grace abounded all the more” (Romans 5:20). The Church sings at the Easter Vigil of Adam’s sin as a “happy fault” (felix culpa), because it won for us so great a Redeemer.