A story is told in circles where science and humor coincide about an ape that was experiencing an acute identity crisis. The troubled primate escaped from the Bronx Zoo and, after sending shock waves of terror through the local community, was found in the New York City Public Library, holding in one hand Darwin’s Origin of the Species and in the other hand a copy of the Book of Genesis. "I just had to find out," he apologetically explained to reporters, "whether I was my keeper’s brother or my brother’s keeper."

Does the ape belong in a zoo as a captive who is cared for by his zoo keeper? Or is he human enough to be thought of on par with human beings?

After Darwin and the Darwinists, it has become easy to make the case that man is a "trousered ape," to borrow the label C.S. Lewis used in his 1947 classic The Abolition of Man and Duncan Williams reused to title his 1972 critique of modern civilization, Trousered Apes.

The correlative difficulty, unfortunately, has been to convince people that man is specifically and uniquely human. The troubled ape in the story, of course, is a stand-in for the human being. Is man descended from apes? Or is he made in the image of God? Hence, the modern dilemma.

Charles Darwin, Walt Disney and Peter Singer make a curious triumvirate. They belong to different "species," one might say, those belonging to the biologist, cartoonist and ethicist, respectively. Yet they all have in common the fact that they have added to the modern confusion concerning the natural identities of man and beast.

When Darwin was 25 years of age, he jotted down in his notebook what was at that time the revolutionary notion that "animals, our fellow brethren in pain, disease, suffering and famine — our slaves in the most laborious works, our companions in our amusements — they may partake of our origin in one common ancestor — we may be all melted together."

Disney humanized animals and could make them appear more human than humans. The death of Bambi’s mother at the hands of merciless hunters created a heightened sympathy for animals and produced as well a considerable flood of tears.

Hugh Hefner hyper-sexualized women when he presented them to the world as "bunnies." In California these days, it is politically incorrect to refer to domesticated animals as "pets" — they are to be referred to as "domestic companions."

Singer’s landmark book Animal Liberation is not only a sustained argument for "animal rights," but also for the superiority of some animals to humans, especially those humans in the early stages of life. He confesses that he can see no reason "why it should be that all humans — including infants, mental defectives, psychopaths, Hitler, Stalin and the rest — have some kind of dignity or worth that no elephant, pig or chimpanzee can ever achieve."

We should not forget, however, that Darwin, Disney, Singer et alia — and not the non-human animals they describe — are the thinkers, the framers and the creators, the only ones who discuss the respective identities of man and beast.

Non-human animals do not speculate, classify or write books. This difference alone separates man from lower animals by light years. We may also add the following characteristics that are distinctive of the human: He is religious, uses a multiplicity of languages, develops science, radically transforms his environment, composes music, lives by a moral code, knows his grandparents and grandchildren, conducts ceremonies, memorializes the dead, honors heroes, philosophizes, tells jokes, laughs at his own foolishness and believes or disbelieves in evolutionary theories.

The list is endless. These characteristics make man different in kind from non-human animals, not simply different in degree.

Perhaps the most thorough and extensively researched investigation into the difference between man and beast ever produced is Mortimer Adler’sThe Difference of Man and the Difference It Makes (1967). This indefatigable researcher, who leaves no stone unturned, comes to the conclusion that the denial of the spiritual, which is necessary in order to reduce man to a purely physical animal, "raises serious if not insuperable difficulties for the metaphysical theory of the will’s freedom, as well as for the philosophical doctrine that freedom of choice is the sine qua non of moral responsibility."

Genesis portrays Adam as a gardener and one who "named the animals." These twin occupations, nonetheless, left him with an aching solitude. Everything God made was "good" — with one exception: "It is not good for man to be alone."

The fact that Adam lived and worked among flora and fauna did not prevent him from being lonely. When Eve was first presented to him, he exclaimed, "This at last is bone of my bone and flesh of my flesh." Finally, in partnership with another human being, Adam had a relationship with a companion who was his equal.

If we believe that human beings are too much like animals, we undervalue them and consequently lower our expectations about how they ought to live and what they ought to do. We then run the risk of treating human beings as we treat livestock.

On the other hand, if we believe that animals are too much like humans, we overvalue them and assign them rights and privileges that are wholly unwarranted. We then run the risk of awarding them benefits that properly belong to humans.

St. Francis of Assisi, the patron saint of ecology and the namesake of Pope Francis, referred to animals as his "brothers" ("brother wolf," "brother fox," etc.). But he also spoke of "brother sun" and "sister moon."

He was honoring the fact that, since all creatures come from God, we owe all our co-creatures a certain "courtesy." By no means, however, was St. Francis a precursor to the Darwinian view of man and animal.

Only man, among creatures on this planet, is made in the image of God. He may be, as Shakespeare described him, the "paragon of animals," but he is their custodian, not their equal.

Nonetheless, he should always be, given his theological and humanitarian nature, a considerate and benevolent custodian.

Donald DeMarco, Ph.D., is a senior fellow of Human Life International.

He is professor emeritus at St. Jerome’s University in Waterloo, Ontario,

and an adjunct professor at Holy Apostles College and Seminary in Cromwell, Connecticut.