The classic "sin" model doesn't do a particularly good job of explaining and predicting human behavior. It's roughly analogous to the ancient four-humours model of medicine. The sin model's traditional prescriptions of prayer, study, church attendance, and willpower (for example) can definitely be useful, but not consistently so; they're essentially folk remedies that seem to work — sometimes — but we don't particularly know why.
The sin model's basic weakness is that our understanding of human behavior is pretty primitive. When people act (or don't act), they're moved by a combination of factors such as biochemistry; physiology; learning; and the phenomenon we call "free will." We know very, very little about how these various factors interact, about how they combine to produce specific behaviors in specific circumstances. The apostle Paul alluded to this problem in Romans 7.15, where he mourned that "I do not understand what I do. For what I want to do, I do not do; but what I hate, I do."
In today's New York Times, Amy Harmon surveys recent research about possible genetic bases for behavior, and notes some important questions that arise as a result: If someone seems genetically predisposed toward certain "bad" behavior, what should we do about it? Should the fact of the predisposition let them off the hook if they do engage in the bad behavior? Harmon's piece is a must-read for any thoughtful person of faith. Excerpt (with emphasis added):
Jason Dallas used to think of his daredevil streak — a love of backcountry skiing, mountain bikes and fast vehicles — as "a personality thing."
Then he heard that scientists at the Fred Hutchinson Cancer Research Center in Seattle had linked risk-taking behavior in mice to a gene. Those without it pranced unprotected along a steel beam instead of huddling in safety like the other mice.
Now Mr. Dallas, a chef in Seattle, is convinced he has a genetic predisposition for risk-taking, a conclusion the researchers say is not unwarranted, since they believe similar variations in human genes can explain why people perceive danger differently. * * *
Mr. Dallas's wife, Mari, for instance, convinced that her husband is in some sense hostage to his daredevil genes, has insisted he draw the line at certain activities. [Ed.: In the sin model, this might be called "avoiding the occasion of sin."]
"If he had his choice, he would be getting a motorcycle," said Ms. Dallas, a pediatric oncologist. "I don't think that's such a good idea." * * *
Friends and family members who worry about behavior that seems unhealthy or self-destructive sometimes suspect that blaming genes is an easy out. When Representative Patrick J. Kennedy, Democrat of Rhode Island, cited his family's history of addiction in admitting to a prescription drug addiction after he crashed his car near the Capitol last month, for instance, some scoffed. "Kennedy blames crash on 'car accident gene,' " read the headline on Antimatternews.com, a satirical blog, an allusion to the 1969 crash in which his father, Senator Edward M. Kennedy, was driving and a passenger was killed. Some bioethicists warn that the embrace of genetics as an explanation for troubling behavior threatens to let society off the hook, too. Taxing cigarettes, banning smoking in bars and not glamorizing it in movies is far more likely to lower smoking rates than drugs tailored to certain genotypes, these critics say.
People could also find their genes being held against them. Already, some scientists suspect a specific gene plays a role in violent behavior, for instance, and a discussion has already begun over how people bearing such genes should be treated.
"If we find a murder mutation, are we going to be more accepting of murderers, or are we going to lock them up even more tightly?" asked Jeffrey M. Friedman, director of the Starr Center for Human Genetics at Rockefeller University. "The more we find genes that play a role in determining all sorts of attributes, the more we're going to face these kinds of ethical issues."