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In a short, inconspicuous paragraph in the conclusion to the first edition of On the Origin of Species, Darwin speculates that “in the distant future … psychology will be based on a new foundation, that of the necessary acquirement of each mental power and capacity by gradation.“ One hundred and forty years later, Darwin's eerie prediction about the revolutionary effect of his work on human beings' self-understanding seems all too prophetic. After a century of dissemination, the once-novel theory of evolution is widely accepted as established scientific fact. Given the quasi-religious hold of evolutionary theory over the modern mind, it is not surprising that it should serve as the spiritual inspiration for developments within the field of psychology. First popularized in the 1970s by Harvard's Edward O. Wilson, evolutionary psychology, originally called sociobiology, interprets all human behavior in light of the evolutionary process. Evolutionary psychology aims to be a comprehensive science, explaining the origins and ends of every human behavior and institution.

Not wanting to be left behind, a number of conservative thinkers have let themselves be caught up in this movement. Conservatism initially identified evolution exclusively with Darwinian materialism and, therefore, viewed it as a fundamental threat to human dignity. But, recently, conservatives such as James Q. Wilson, Francis Fukuyama, and Charles Murray have used evolutionary psychology to show that morality is rooted in human biology. Fukuyama's The Great Disruption goes so far as to claim that “a great deal of social behavior is not learned but part of the genetic inheritance of man and his great ape forbears.” Drawing on categories borrowed from evolutionary psychology, Fukuyama argues that human beings are drawn to the kind of moral order provided by traditional rules of trust and honesty.

Evolution's most ambitious and vocal conservative advocate, however, is political scientist Larry Arnhart. But where Wilson and Fukuyama speak of evolution generally, Arnhart appeals directly to Darwin himself. In Darwinian Natural Right: The Biological Ethics of Human Nature, Arnhart argues that conservative thought has fundamentally misunderstood Darwin. For Arnhart, Darwin is not a biological materialist but a modern disciple of Aristotle. Properly understood, Darwinism proves that morality is rooted in human biology. Indeed, Arnhart claims that Darwinism can identify twenty biological desires that are common to all human societies. The fulfillment or frustration of these desires provides universal standards for judging the morality of human social behavior. Darwinian natural right consists of the “right” to have these biological desires satisfied. Arnhart recently argued in the conservative religious journal First Things that both secular and religious conservatives currently “need Charles Darwin.” By “adopting a Darwinian view of human nature,” both groups would be able to give a rational, non-sectarian response to the prevailing dogma of moral relativism. For Arnhart, the attraction of Darwinism is essentially practical: It provides a “scientific”–not “metaphysical” or “sectarian”–basis for “conservative moral and political thought.”

One has to question, however, the wisdom of evaluating any account of human nature primarily in terms of its political utility. But this does explain why, on every critical point, Arnhart lets his political concerns shape his theoretical defense of Darwinism. Consequently, Arnhart never really confronts conservatism's original charge that Darwinism reduces human beings to clever, biologically determined animals. But he does present natural lawyers with an intriguing and, by no means, inconsequential choice: Should they embrace Darwinism and give natural law conclusions the air of “scientific legitimacy,” or should they continue to defend an unfashionable but richer account of human nature that transcends human biology?

The Biology of Morality

Essential to the Darwinian defense of morality is the belief that social behaviors are “biologically rooted” in human nature. Darwinians such as Arnhart start from the premise that human beings are “hard-wired” for specific species-preserving behaviors. Darwinism explains all human societies, ranging from families to political communities, as unintended byproducts of the evolutionary process. Social behaviors and institutions came into existence as evolutionary responses to “species-threatening” changes in man's environment. Friendships, marriages, families, and even political communities, all of which are commonly seen as vital features of a meaningful human life, have their origins outside of the moral universe. Every society came into existence in a world where “species-survival” and “species-extinction,” not good and evil, were the fundamental human categories. Darwinism views sociality and morality as part of man's genetic inheritance–the adaptive means through which the species perpetuates itself. Contrary to popular belief, morality is really instrumental to the larger goal of individual and collective preservation.

Darwin's thesis that all species, including the human species, possess a biological drive for self-preservation is not novel. Arnhart, for example, frequently observes that Saint Thomas Aquinas, the natural law's classical exponent par excellence, makes a similar claim. And as Arnhart likes to note, Aquinas even once described natural right as “that which nature has taught to all animals.” Aquinas's strongest statement on this matter, however, occurs in the context of a wider discussion of natural law. Aquinas there states that the natural law's second inclination, which man shares with all animals, directs him to preserve the species. But as Arnhart shows, Darwin extends this insight substantially further than Aquinas does. In contrast to Aquinas, Darwin believes that those behaviors that are necessary for the survival of the species gradually become woven into human biology itself. Over time, human beings eventually come to view behaviors that are necessary for survival as both meaningful and moral.

The Darwinian defense of morality characteristically points to the end of the family as illustrative of how morality is rooted in human biology. Arnhart himself traces the family back to the strong sexual drive of young men. Rooted in their “biological nature,” this drive plays an important role in the preservation of the species, yet it also fulfills “the natural desire for conjugal bonding.” Once properly channeled (Arnhart conspicuously never explains how or why this occurs), the sexual drive allows for the kind of bonding that naturally occurs within the family. The preservation of the family and, ultimately, of the species itself are the result of the “biological drive for sexual mating.” Scrutinized from the Darwinian perspective, the biological desire for conjugal bonding is revealed to perform the necessary task of stabilizing society.

While Darwinism can defend the family as a natural institution, it is not a genuinely moral or spiritual defense. Wedded to biological materialism, Darwinism necessarily reduces the good to the useful–finally viewing the family as instrumental to evolution's larger goal of the preservation of society. While family life undoubtedly helps stabilize society, this clearly is not the only thing that is good about it. Arnhart's recognition of natural desires for “conjugal and familial bonding” shows that he is aware of this fact. But the logic of his position ultimately requires him to view the family in terms of its preservation of society.

The Morality of Biology

But is this really compatible with conservatism? Is it really possible to understand family life solely in terms of its role in the preservation of society? Setting aside for the moment any sacramental notion of marriage(not mere conjugal bonding) and family life, Darwinism would have one believe that a husband's self-conscious love for his wife or the personal sacrifices that parents willingly make for their children are byproducts of a primordial desire to perpetuate the species. Viewed from the perspective of human beings' lived experience, Darwinism's appreciation of the family is even more dehumanizing than modernity's view of marriage as simply a contractual arrangement.

Part of the reason for this flattening of the human horizon is Darwinism's systematic identification of the good with the flourishing of the species rather than with the self-conscious individual. There is then something fundamentally incoherent about the effort to defend the intrinsic goodness of morality on the basis of Darwinism. This incoherence, however, explains a number of oddities about the Darwinian defense of morality. The most obvious of these is its creative effort to present Darwin as a teacher of “evolution.” As surprising as it sounds, Darwin never uses this term in The Origin of Species. Rather, he speaks of “descent with modification.” The difference between these terms is not merely semantic. Darwin realized that evolution is a teleological term. To say that something evolved is to say that it has evolved toward something. Evolution implies the kind of purposeful change by which something unfolds according to a prearranged plan–precisely the understanding of evolution that the Roman Catholic Church claims is not necessarily inimical to Christianity. While often popularly misunderstood, what the Catholic Church consistently has opposed, from Pius XII's nuanced 1950 encyclical Humani Generis to John Paul II's recent statements, is not the idea of evolution per se but, rather, those materialist theories that reduce psychic humanity to biological animality.

Darwin, however, eschews such teleological thinking–going so far as to note in his manuscript not to use “hierarchical” terms such as higher and lower. For him, nature is intrinsically mechanistic. Change results from “natural selection,” the process by which species adapt to environmental changes by weeding out variations that jeopardize their survival. Far from acting towards an end, nature responds to external forces of chance and necessity. It is not difficult to see why Darwinians such as Arnhart try to gloss over the harshness of this teaching. By drawing attention to the fact that nature is a blind and continuous process, they effectively undermine their political defense of the intrinsic goodness of morality.

Darwinism's teaching on perpetual modification points to another problem with the idea of Darwinian natural law. For Darwin, the process of modification is, in principle, continuous. Contrary to what they may wish to believe, human beings are not the end of the evolutionary process. The Darwinian defense of natural morality, therefore, is not to be taken too literally. Lacking the fixity of any genuine end, the goods supported by natural law are useful only over long periods of time. Like nature itself, they are transitionally good. This explains why Arnhart places so much emphasis on biology, since it offers the only real source of “temporary fixity” in the world.

Natural Law and the Humanization of Biology

What is most striking about the Darwinian defense of morality is that it argues for one of the positions that natural law traditionally has argued against. Natural law historically has opposed any simplistic identification of the natural with the biological. Contrary to Darwinism's identification of the natural with the instinctual, natural law associates the natural with the reasonable. It seeks to humanize and transcend the realm of biology by incorporating it into the realm of reason–to view the low in light of the high, not vice versa. Whereas materialist Darwinians see human nature culminating in the biological instinct to perpetuate the species, Aquinas thinks that man's natural inclination directs him to seek the truth about God and to live in society. Rather than insisting that he be completely at home in the biological world, natural law realizes that his natural desire for transcendence ensures that man can only be ambiguously at home in the world. Psychically different from other creatures, the rational creature (not merely the calculating, species-preserving animal) somehow embodies all of the aspirations of the evolved biological world.

This natural desire to know does not negate the desire to perpetuate the species but, in fact, can explain why such perpetuation is desirable. Part of the attraction of natural law thinking, therefore, lies in its ability to show that human beings are not slaves to their instincts but, rather, that they possess the psychic freedom to make sense of these instincts. Over and against Darwinism's biological determinism, natural law theory is grounded in the all-too-human experience of wrestling with matters of conscience–of trying to do what one ought to do and not merely what one instinctively wants to do. Rejecting the reality of such an inner life, Darwinian-based defenses of morality are necessarily self-defeating. They replace relativism's belief that nothing can legitimately make a claim on the human soul with materialism's belief that human beings are biologically incapable of caring about their souls.

Near the end of his essay in First Things, Arnhart celebrates the remarkable recent advances of science in the areas of neurobiology and genetics. In light of these advances, Arnhart warns that “if conservatism is to remain intellectually vital, [it] will need to show that [its] position is compatible with this new science of human nature.” But what does Arnhart think Darwinism has to say to these new sciences? If there really are no natural limits on human beings, if nature really is in a constant slow state of flux, how can a Darwinian, even a morally serious Darwinian, oppose something such as the “new science” of human cloning? A self-conscious Darwinian such as E. O. Wilson realizes that cloning is simply the next stage of human “modification.” Faithful to the spirit of his Darwinism, Wilson looks forward to the day when cloning or “volitional evolution” will allow scientists to alter “not just the anatomy and intelligence of the species but also the emotions and creative drive that compose the very core of human nature.” Less consistent Darwinians such as Arnhart choose to remain blissfully unaware of this fact. Consequently, they fail to recognize that what they offer is not so much up-to-date moral guidance as the ultimate moral justification for the “brave new world.”

Marc D. Guerra is an assistant professor in theology at Assumption College in Worcester, MA. He may be contacted at