That the body evolved from some lower form to the human body can be argued several ways. First, God uses secondary causes wherever possible. Second, there is a universal hierarchy in which the lower is in service of the higher, and has an appetite for the higher. Third, there is a reasonable philosophical explanation of how the evolution of the body of man could take place, Klubertanz’s theory of passive evolution under the influence of God. Fourth, the general opinion of Neo-Scholastics concerning the evolution of the human body has changed as manifest by the International Congress in Rome, 23 to 24 April 2002, at the Pontifical Atheneum Regina Apsotoloum.

First, God uses secondary causes whenever possible.⁴¹ St. Thomas teaches that God, like a good governor, does not do everything Himself. First, if God did everything Himself, creatures in the world would be deprived of causality. Second, if God did everything Himself, our personal experience of our own personal causality would be a false perception. Third, if God did everything Himself there were be little or no basis for personal responsibility, ethics, or morality. Fourth, there is already a philosophical system rejected by the Neo-Scholastics, called Occasionalism, which has creatures as only the occasion of divine action and God the only true cause of everything. Fifth, other Neo-Scholastics, such as La Vecchia at the Gregorian University in Rome, believe this view of secondary causality can be applied to the evolution of the body of man.⁴²

Second, there is a universal hierarchy in which the lower is in service of the higher, and has an appetite for the higher.⁴³ Hugon holds that there is an ontological nexus, by reason of nature, for the world as it moves to the same goal.⁴⁴ Hugon describes this as first a "to be" in minerals, to which is added "to live" in vegetable life, to which is added "to sense" in animal life, so that man has "to be," "to live," "to sense," and "to reason." Hugon notes that this was so common a philosophic opinion that the Scholastics had an axiom, "The top of the inferior touches the lowest superior."⁴⁵ Gilson also endorses such a universal hierarchy: "That hierarchy is not based on the assumption that the lower possesses whatever the higher possesses, but on the fact that the lower has a feeble participation in what the higher possesses. Thus the animal, whose nature is purely sensitive, is deprived of reason but is endowed with a kind of prudence and natural power to evaluate which is a feeble participation in human reason."⁴⁶ Benignus comments on the text of St. Thomas (Aquinas Summa Contra Gentiles 3. 22). Benignus says, "The Angelic Doctor is teaching something that is very relevant to the problem of evolution, something that makes evolution intelligible. What he is teaching is that primary matter is appetite or urge to live and ultimately to live on the highest possible level, that is to say the body of man."⁴⁷

Third, Klubertanz has been able to give a reasonable philosophical explanation of how the evolution of the body of man could take place. The Neo-Scholastic, Joseph Gredt, in 1909, argued against the evolution of the human body. However, by 1953, the attitude of some Neo-Scholastics had changed. Klubertanz argues that "it seems possible that the human body could take its rise in this way," by equivocal causality, chance, and Providence. Even Klubertanz admits that the complexity of the interference of the equivocal causality would be staggering, but it does not seem impossible.⁴⁸

What is the general theory of Klubertanz? He affirms essential evolution of living things up to and including the human body (the whole man with his spiritual soul excluded) through equivocal causality, chance and Providence.⁴⁹ This is a possible explanation of the origin of living things.

How does Klubertanz specifically envision the possibility of human body evolution? Either during the formation of the germ cells, or at the moment of their union, the material parts undergo such a modification that they become like the human ovum and sperm, or the fertilized human ovum. Then at the instant when the proper material dispositions are present in this being, God would create in the matter, in this way essentially disposed, a human soul, in the same way He creates the soul in the course of normal human generation. Klubertanz reminds his readers that it is impossible to say what did occur.

Fourth, Neo-Scholastics now commonly hold the philosophical possibility of the evolution of the body of man. Even in 1959, Palmes noted that Christian Evolutionists, even Catholics, admit creation by God, at least of primordial matter... and by generation and progressive transformation descended diverse actual organisms and even the body (organismus hominis) of man, except however the human soul, which as spiritual would only be able to be created by God."⁵⁰ During the International Congress in Rome, 23 to 24 April 2002, at the Pontifical Atheneum Regina Apostolorum, Fiorenza Facchini delivered a paper entitled "The Emergence of Man." In his English Summary, Facchini noted "...the physical conditions necessary (fit environment, development of the brain), with particular reference to the Australopithecines, among which the lineage that brought to the human beings can be individuated...These are arguments to consider that documents of cultural behavior are already found with Homo habilis. They become more evident with Homo erectus and above all with Homo sapiens."⁵¹