On questions about biological evolution, both the Magisterium of the Catholic Church and Thomist philosophers and theologians have tended carefully to steer a middle course. On the one hand, they have allowed that a fairly wide range of biological phenomena may in principle be susceptible of evolutionary explanation, consistent with Catholic doctrine and Thomistic metaphysics. On the other hand, they have also insisted, on philosophical and theological grounds, that not every biological phenomenon can be given an evolutionary explanation, and they refuse to issue a “blank check” to a purely naturalistic construal of evolution. Evolutionary explanations are invariably a mixture of empirical and philosophical considerations. Properly to be understood, the empirical considerations have to be situated within a sound metaphysics and philosophy of nature.
For the Thomist, this will have to include the doctrine of the four causes, the principle of proportionate causality, the distinction between primary and secondary causality, and the other key notions of Aristotelian-Thomistic (A-T) metaphysics and philosophy of nature (detailed defense of which can be found in Scholastic Metaphysics). All of this is perfectly consistent with the empirical evidence, and those who claim otherwise are really implicitly appealing to their own alternative, naturalistic metaphysical assumptions rather than to empirical science. (Some earlier posts bringing A-T philosophical notions to bear on biological phenomena can be found here, here, here, here, and here. As longtime readers know, A-T objections to naturalism have absolutely nothing to do with “Intelligent Design” theory, and A-T philosophers are often very critical of ID. Posts on the dispute between A-T and ID can be found collected here.)
On the subject of human origins, both the Magisterium and Thomist philosophers have acknowledged that an evolutionary explanation of the origin of the human body is consistent with non-negotiable theological and philosophical principles. However, since the intellect can be shown on purely philosophical grounds to be immaterial, it is impossible in principle for the intellect to have arisen through evolution. And since the intellect is the chief power of the human soul, it is therefore impossible in principle for the human soul to have arisen through evolution. Indeed, given its nature the human soul has to be specially created and infused into the body by God -- not only in the case of the first human being but with every human being. Hence the Magisterium and Thomist philosophers have held that special divine action was necessary at the beginning of the human race in order for the human soul, and thus a true human being, to have come into existence even given the supposition that the matter into which the soul was infused had arisen via evolutionary processes from non-human ancestors.
In a recent article at Crisis magazine, Prof. Dennis Bonnette correctly notes that Catholic teaching also requires that there be a single pair from whom all human beings have inherited the stain of original sin. He also rightly complains that too many Catholics wrongly suppose that this teaching can be allegorized away and the standard naturalistic story about human origins accepted wholesale.
The sober middle ground
Naturally, that raises the question of how the traditional teaching about original sin can be reconciled with what contemporary biologists have to say about human origins. I’ll return to that subject in a moment. But first, it is important to emphasize that the range of possible views consistent with Catholic teaching and A-T metaphysics is very wide, but also not indefinitely wide. Some traditionalist Catholics seem to think that the willingness of the Magisterium and of contemporary Thomist philosophers to be open to evolutionary explanations is a novelty introduced after Vatican II. That is simply not the case. Many other Catholics seem to think that Pope St. John Paul II gave carte blanche to Catholics to accept whatever claims about evolution contemporary biologists happen to make in the name of science. That is also simply not the case. The Catholic position, and the Thomist position, is the middle ground one I have been describing. It allows for a fairly wide range of debate about what kinds of evolutionary explanations might be possible and, if possible, plausible; but it also rules out, in principle, a completely naturalistic understanding of evolution.
Perhaps the best-known magisterial statement on these matters is that of Pope Pius XII in his 1950 encyclical Humani Generis. In sections 36-37 he says:
[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. However, this must be done in such a way that the reasons for both opinions, that is, those favorable and those unfavorable to evolution, be weighed and judged with the necessary seriousness, moderation and measure, and provided that all are prepared to submit to the judgment of the Church…
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.
The pope here allows for the possibility of an evolutionary explanation of the human body and also, in strong terms, rules out both any evolutionary explanation for the human soul and any denial that human beings have a single man as their common ancestor. This combination of theses was common in Thomistic philosophy and in orthodox Catholic theology at this time, and can be found in Neo-Scholastic era manuals published, with the Imprimatur, both before 1950 and in the years after Humani Generis but before Vatican II.
For example, in Celestine Bittle’s The Whole Man: Psychology, published in 1945, we find:
[T]he evolution of man’s body could, per se, have been included in the general scheme of the evolutionary process of all organisms. Evolution would be a fair working hypothesis, because it makes little difference whether God created man directly or used the indirect method of evolution…
Whatever may be the ultimate verdict of science and philosophy concerning the origin of man’s body, whether through organic evolution or through a special act of divine intervention, man’s soul is not the product of evolution. (p. 585)
George Klubertanz, in Philosophy of Human Nature(1953), writes:
Essential evolution of living things up to and including the human body (the whole man with his spiritual soul excluded…), as explained through equivocal causality, chance, and Providence, is a possible explanation of the origin of those living things. The possibility of this mode of origin can be admitted by both philosopher and theologian. (p. 425)
Klubertanz adds in a footnote:
There are some theological problems involved in such an admission; these problems do not concern us here. Suffice it to say that at least some competent theologians think these problems can be solved; at any rate, a difficulty does not of itself constitute a refutation.
At the end of two chapters analyzing the metaphysics of evolution from a Thomistic point of view, Henry Koren, in his indispensible An Introduction to the Philosophy of Animate Nature (1955), concludes:
[T]here would seem to be no philosophical objection against any theory which holds that even widely different kinds of animals (or plants) have originated from primitive organisms through the forces of matter inherent to these organisms and other material agents…
Even in the case of man there appears to be no reason why the evolution of his body from primitive organisms (and even from inanimate matter) must be considered to be philosophically impossible. Of course… man’s soul can have obtained its existence only through a direct act of creation; therefore, it is impossible for the human soul to have evolved from matter. In a certain sense, even the human body must be said to be the result of an act of creation. For the human body is made specifically human by the human soul, and the soul is created; hence as a human body, man’s body results from creation. But the question is whether the matter of his body had to be made suitable for actuation by a rational soul through God’s special intervention, or if the same result could have been achieved by the forces of nature acting as directed by God. As we have seen… there seems to be no reason why the second alternative would have to be an impossibility. (pp. 302-4)
Adolphe Tanquerey, in Volume I of A Manual of Dogmatic Theology (1959), writes:
It is de fide that our first parents in regard to body and in regard to soul were created by God: it is certain that their souls were created immediately by God; the opinion, once common, which asserts that even man’s body was formed immediately by God has now fallen into controversy…
As long as the spiritual origin of the human soul is correctly preserved, the differences of body between man and ape do not oppose the origin of the human body from animality…
The opinion which asserts that the human body has arisen from animality through the forces of evolution is not heretical, in fact in can be admitted theologically…
Thesis: The universal human race has arisen from the one first parent Adam. According to many theologians this statement is proximate to a matter of faith. (pp. 394-98)
Similarly, Ludwig Ott’s well-known Fundamentals of Catholic Dogma, in the 1960 fourth edition, states:
The soul of the first man was created immediately by God out of nothing. As regards the body, its immediate formation from inorganic stuff by God cannot be maintained with certainty. Fundamentally, the possibility exists that God breathed the spiritual soul into an organic stuff, that is, into an originally animal body…
The Encyclical “Humani generis” of Pius XII (1950) lays down that the question of the origin of the human body is open to free research by natural scientists and theologians…
Against… the view of certain modern scientists, according to which the various races are derived from several separated stems (polygenism), the Church teaches that the first human beings, Adam and Eve, are the progenitors of the whole human race (monogenism). The teaching of the unity of the human race is not, indeed, a dogma, but it is a necessary pre-supposition of the dogma of Original Sin and Redemption. (pp. 94-96)
J. F. Donceel, in Philosophical Psychology(1961), writes:
Until a hundred years ago it was traditionally held that the matter into which God for the first time infused a human soul was inorganic matter (the dust of the earth). We have now very good scientific reasons for admitting that this matter was, in reality, organic matter -- that is, the body of some apelike animal.
Aquinas held that some time during the course of pregnancy God infuses a human soul into the embryo which, until then, has been a simple animal organism, albeit endowed with human finality. The theory of evolution extends to phylogeny what Aquinas held for ontogeny.
Hence there is no philosophical difficulty against the hypothesis which asserts that the first human soul was infused by God into the body of an animal possessing an organization which was very similar to that of man. (p. 356)
You get the idea. It is in light of this tradition that we should understand what Pope John Paul II said in 1996 in a “Message to the Pontifical Academy of Sciences.” The relevant passages are as follows:
In his encyclical Humani Generis (1950), my predecessor Pius XII has already affirmed that there is no conflict between evolution and the doctrine of the faith regarding man and his vocation, provided that we do not lose sight of certain fixed points…
Today, more than a half-century after the appearance of that encyclical, some new findings lead us toward the recognition of evolution as more than an hypothesis. In fact it is remarkable that this theory has had progressively greater influence on the spirit of researchers, following a series of discoveries in different scholarly disciplines. The convergence in the results of these independent studies -- which was neither planned nor sought -- constitutes in itself a significant argument in favor of the theory…
[T]he elaboration of a theory such as that of evolution, while obedient to the need for consistency with the observed data, must also involve importing some ideas from the philosophy of nature.
And to tell the truth, rather than speaking about the theory of evolution, it is more accurate to speak of the theories of evolution. The use of the plural is required here -- in part because of the diversity of explanations regarding the mechanism of evolution, and in part because of the diversity of philosophies involved. There are materialist and reductionist theories, as well as spiritualist theories. Here the final judgment is within the competence of philosophy and, beyond that, of theology…
Pius XII underlined the essential point: if the origin of the human body comes through living matter which existed previously, the spiritual soul is created directly by God…
As a result, the theories of evolution which, because of the philosophies which inspire them, regard the spirit either as emerging from the forces of living matter, or as a simple epiphenomenon of that matter, are incompatible with the truth about man.
End quote. Some traditionalists and theological liberals alike seem to regard John Paul’s statement here as a novel concession to modernism, but it is nothing of the kind. The remark that evolution is “more than an hypothesis” certainly expresses more confidence in the theory than Pius had, but both Pius’s and John Paul’s judgments on that particular issue are merely prudential judgments about the weight of the empirical evidence. At the level of principle there is no difference between them. Both popes affirm that the human body may have arisen via evolution, both affirm that the human soul did not so arise, and both refuse to accept the metaphysical naturalist’s understanding of evolution. John Paul II is especially clear on this last point. As you would expect from a Thomist, he rightly insists that evolutionary explanations are never purely empirical but all presuppose alternative background metaphysical assumptions. Hence he notes that a fully worked out theory of evolution “must also involve importing some ideas from the philosophy of nature” and that here “the final judgment is within the competence of philosophy and, beyond that, of theology” -- not empirical science per se. And as Bonnette notes, the Catechism issued under Pope John Paul II essentially reaffirms, in the relevant sections (396-406), the traditional teaching that the human race inherited the stain of original sin from one man.
Neither those conservative Catholics who would in principle rule out any evolutionary aspect to human origins, nor those liberal Catholics who would rule out submitting the claims made by contemporary evolutionary biologists to any philosophical or theological criticism, can find support in the teaching of either of these popes.
Monogenism or polygenism?
But again, how can the doctrine of original sin be reconciled with what contemporary biology says about human origins? For the doctrine requires descent from a single original ancestor, whereas contemporary biologists hold that the genetic evidence indicates that modern humans descended from a population of at least several thousand individuals.
This is an issue I addressed a few years ago in a series of posts (here, here, and here). Longtime readers will recall that I there rehearsed a proposal developed by Mike Flynn and Kenneth Kemp to the effect that we need to distinguish the notion of a creature which is human in a strict metaphysicalsense from that of a creature which is “human” merely in a looser, purely physiological sense. The latter sort of creature would be more or less just like us in its bodily attributes but would lack our intellectual powers, which are incorporeal. In short, it would lack a human soul. Hence, though genetically it would appear human, it would not be a rational animal and thus notbe human in the strict metaphysical sense. Now, this physiologically “human” but non-rational sort of creature is essentially what Pius XII, John Paul II, and the philosophers and theologians quoted above have in mind when they speak of a scenario in which the human body arises via evolutionary processes.
The Flynn-Kemp proposal is this. Suppose evolutionary processes gave rise to a population of several thousand creatures of this non-rational but genetically and physiologically “human” sort. Suppose further that God infused rational souls into two of these creatures, thereby giving them our distinctive intellectual and volitional powers and making them truly human. Call this pair “Adam” and “Eve.” Adam and Eve have descendents, and God infuses into each of them rational souls of their own, so that they too are human in the strict metaphysical sense. Suppose that some of these descendents interbreed with creatures of the non-rational but genetically and physiologically “human” sort. The offspring that result would also have rational souls since they have Adam and Eve as ancestors (even if they also have non-rational creatures as ancestors). This interbreeding carries on for some time, but eventually the population of non-rational but genetically and physiologically “human” creatures dies out, leaving only those creatures who are human in the strict metaphysical sense.
On this scenario, the modern human population has the genes it does because it is descended from this group of several thousand individuals, initially only two of whom had rational or human souls. But only those later individuals who had this pair among their ancestors (even if they also had as ancestors members of the original group which did not have human souls) have descendents living today. In that sense, every modern human is both descended from an original population of several thousand and from an original pair. There is no contradiction, because the claim that modern humans are descended from an original pair does not entail that they received all their genes from that pair alone.
Of course, this is speculative. No one is claiming to know that this is actually what happened, or that Catholic teaching requiresthis specific scenario. The point is just that it shows, in a way consistent with what Catholic orthodoxy and Thomistic philosophy allow vis-à-vis evolution, that the genetic evidence is not in fact in conflict with the doctrine of original sin. Naturally other Catholics and Thomists might reasonably disagree with it.
Having said that, I have yet to see any plausible objections to the Flynn-Kemp scenario. This brings us back to Prof. Bonnette’s article. In response to the Flynn-Kemp proposal, he writes:
The difficulty with any interbreeding solution (save, perhaps, in rare instances) is that it would place at the human race’s very beginning a severe impediment to its healthy growth and development. Natural law requires that marriage and procreation take place solely between a man and a woman, so that children are given proper role models for adult life. So too, even if the union between a true human and a subhuman primate were not merely transitory, but lasting, the defective parenting and role model of a parent who is not a true human being would introduce serious disorder in the proper functioning of the family and education of children. Hence, widespread interbreeding is not an acceptable solution to the problem of genetic diversity.
Moreover, given the marked reduction in the number of ancient HLA-DRB1 alleles found by the later genetic studies of Bergström and von Salomé, it may turn out that no interbreeding is needed at all, or at most, that very rare instances of it may have occurred. Such rare events might not even entail the consent of true human beings, since they could result from an attack by a subhuman male upon a non-consenting human female.
I put to one side Prof. Bonnette’s remarks about the genetic evidence, which I’ll leave to the biologists to evaluate. Bonnette allows that some interbreeding may have occurred, but he claims that it cannot have been “widespread” and that the reason has to do with natural law. But what is the problem, exactly?
Back in 2011, when Flynn, Kemp, and I first wrote on this topic and the Flynn-Kemp proposal was getting a lot of attention in the blogosphere, some people objected that interbreeding of the sort in question amounted to bestiality. But of course, no one is suggesting that we should approve of the interbreeding in question. The claim is merely that in fact it may have happened, even if this was contrary to natural and divine law (just as Cain killed Abel even though this was contrary to the natural law, and just as Adam and Eve ate of the fruit of the Tree of Knowledge, even though this was contrary to divine law).
Nor would it be a good objection to suggest that no one would plausibly have been tempted to engage in such interbreeding. After all, the scenario in question would hardly be comparable to that of the average member of contemporary civilization being tempted to have sex with an ape, which would of course not be psychologically plausible. For one thing, the sub-rational but genetically and physiologically “human” creatures in question would notbe like apes, or indeed like any of the non-human animals with which we are familiar. They would more or less look like us. Furthermore, they would even act like us to some degree. As I noted in a recent post, though a purely material system could never in principle exhibit true rationality, it might simulateit to a significant extent (just as if you add enough sides to a polygon you will get something that looks like a circle even though it could not really be a circle). The sub-rational creatures in question would have been sphexish, but a sufficiently complex sphexish creature might seem not to be on a superficial examination. Recall Popper’s distinction between four functions of language: expressive, signaling, descriptive, and argumentative. The sub-rational creatures in question would not be capable of the latter two functions (which presuppose rationality) but they might have exhibited very sophisticated versions of the first two functions.
Meanwhile, the earliest true humans would not have had anything like the modern civilizational accompaniments of sexual activity, especially given the effects of original sin. Obviously it would be absurd to think of their liaisons as involving smooth techniques of romantic seduction, contemporary standards of personal hygiene, etc. So, the cultural “distance” between primitive true human beings and the sub-rational creatures in question need not have been so great as to make the sexual temptation psychologically implausible. It might have been comparable to a very uncultured and unsophisticated person taking sexual advantage of an even more unsophisticated and indeed very stupid person. Not that it was exactly like that, since even a stupid person is still intelligent in the strict sense, whereas the sub-rational creatures in question wouldn’t even rise to the level of stupidity. The point is that the situation could have been psychologically close enough to that for the temptation to be real. (As I indicated, partly in jest, in one of the earlier posts, we might think on the model of Charlton Heston’s character “Taylor” being attracted to the Linda Harrison character “Nova” in Planet of the Apes -- not that the early sub-rational creatures would have looked quite that good!)
It doesn’t seem that the “bestiality” issue per se is really the heart of Prof. Bonnette’s objection, though. His point seems instead to be that a “union” of a true human being with a sub-rational creature of the sort in question would be dysfunctional vis-à-vis the proper rearing of truly human children. This is true, but it is hard to see how it is a problem for the Flynn-Kemp scenario, for nothing in that scenario requires that such “unions” be anywhere close to optimal from a child-rearing point of view, or even that there be “unions” (of some long-term sort) in the first place. All that it requires is that there was enough interbreeding to account for the genetic evidence appealed to by contemporary biologists. It isn’t clear how the question of whether, how, and to what extent the sub-rational creatures were involved in child-rearing affects the judgment that there was sufficient interbreeding.
Perhaps Bonnette thinks that child-rearing would have been so deficient that the population of true humans could not have survived long enough to displace the sub-rational creatures. But it is hard to see why. Surely the child of a “union” between a true human being and one of the sub-rational creatures would have an advantage over the offspring of two sub-rational creatures, for such a child would itself have rationality and at least one rational parent, whereas the other sort of offspring would have neither. Moreover, we needn’t think in terms of such pairings in the first place. Why not think instead of a scenario where a truly human male forms a union with a truly human female but also has several sub-rational but genetically and physiologically “human” females as concubines, where the resulting children are all essentially reared by the human couple? And such arrangements need only have occurred frequently enough for the truly human population to supplant the population of sub-rational creatures. There is no need to flesh out the Flynn-Kemp scenario in the specific way Bonnette (apparently) does.
So, it seems to me that neither Prof. Bonnette nor anyone else has raised any serious difficulty for the Flynn-Kemp proposal. However, Prof. Bonnette is right to hold that many Catholics need to show greater caution when commenting on matters pertaining to evolution.
