In her new and buzzworthy book, For Better: The Science of a Good Marriage, The New York Times's Tara Parker-Pope examines what brain chemistry and genes have to do with happy marriages. She begins a recent Well column with a question: "Why do some men and women cheat on their partners while others resist the temptation?" While she doesn't come right out with an answer, she implies that the inclination toward adultery lies in our genes. Some researchers have dubbed the gene that predicts whether or not we will cheat the "fidelity gene" (though, as Parker-Pope notes, the label is a misnomer, since the study sets out to measure marital stability, not faithfulness). Her research shows that men with a variant of this gene are less likely to be in committed relationships and more likely to be in unhappy marriages.

Genetics. It's a modern answer to an age-old question. In the past, other explanations have been proposed for immoral human behavior. First come spiritual explanations, perhaps best summed up by the phrase "the Devil made me do it." Psychological explanations connect our behavior as adults to events that happened in our past. In recent years, biology has joined the list of reasons why humans behave badly.

Of course, none of these explanations are problematic in and of themselves. And none of them should surprise Christians. All aspects of our human nature are fallen, inclined to turn away from God's good intentions for us. The problem comes when we reduce human behavior to any one of these explanations.

The Bible attests that we are physical, social, spiritual, emotional, and psychological beings at once. The complexity of our humanity has challenged Christians throughout church history. In the first few centuries of Christianity, some believers wanted to deny the significance of the body, claiming that our spiritual dimension was more significant and that Christ would liberate us from our bodies. Over and against this reasoning (eventually denounced as heresy) came the doctrine of the bodily resurrection of Jesus, and, in the fullness of time, of all of creation. The spirit matters, affirmed the early church, but only as it is integrated with the physical.

Well, the pendulum has swung in the other direction. Science is today's reigning explanatory paradigm, the ultimate lens we use to understand reality and ourselves. As a result, the biological explanation for behavior can quickly become divorced from the spiritual. Instead of ignoring the physical, we reduce the human person to genes and chemical reactions. Since we can't "prove" the existence of the Holy Spirit or the human soul using scientific means, the spiritual gets sidelined to the realm of conjecture or opinion, while the physical becomes factual, real, true.

There is nothing wrong with acknowledging a genetic component in our moral choices. Some people are more likely to become alcoholics, others to express anger with violence, others to cheat on their spouses. The danger comes when we don't acknowledge the wholeness of the human person, the complexity of our wills, and the fundamental spiritual reality that we are created in God's image. Parker-Pope nods to this complexity when she writes, "While there may be genetic differences that influence commitment, other studies suggest that the brain can be trained to resist temptation."

A Christian understanding of both temptation and fidelity goes further. It is God's grace and the Spirit at work within us that enable us to resist temptation. Sure, those temptations come in different forms. But whatever the biological basis for temptation, the means of overcoming it involves more than changing behavior. It involves training the brain, yes, but training the brain in a spiritual way. As Paul writes, "Finally, brothers, whatever is true, whatever is noble, whatever is right, whatever is pure, whatever is lovely, whatever is admirable—if anything is excellent or praiseworthy—think about such things" (Phil 4:8) and, "Do not conform any longer to the pattern of this world, but be transformed by the renewing of your mind" (Rom. 12:2).

Finally, understanding the human as comprising body, mind, and spirit offers a different rationale for why we resist temptation. Parker-Pope never makes an argument for fidelity or for why it matters if people resist temptation. I suppose she would say that faithful relationships lead to social stability, happy children, perhaps even self-fulfillment. Toward the end of her article, she writes, "it may not be feelings of love or loyalty that keep couples together. Instead, scientists speculate that your level of commitment may depend on how much a partner enhances your life and broadens your horizons—a concept that Arthur Aron, a psychologist and relationship researcher at Stony Brook University, calls 'self-expansion.' " For Parker-Pope, fidelity is still, ultimately, about the self.

Christians understand marriage as a union before God. Yes, he intended it to provide social stability and personal well-being. But it is also intended to mirror the love that Christ has for his body, the church. Faithfulness in human relationships is meant to give flesh to the faithfulness of God. Here again, on a grander scale, the physical is linked to the spiritual and the emotional. Research that unearths the biology behind immoral choices helps us understand one aspect of our humanity, but such research is only helpful if it is integrated with a holistic understanding of the human as a creature, a soul whose life has been given by God.

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