Nature or Nurture? The Surprising Way Genetics Could Reshape the Debate.

What’s the Big Idea?

Will red wine really make you live longer? Does coffee strengthen brainpower or turn bones to dust? (Yes! No! Maybe.) For every scientific study proclaiming that something is good for you, there’s an equally plausible study that says it will kill you. The reason, according to Jason Fletcher of the Yale School of Public Health, is that flavor-of-the-week research is based on correlation, or an indicative relationship among data, rather than causality – a difference that is as statistically significant as the one between “probably” and “beyond a reasonable doubt.” 

The gold standard for experiments is the randomized control trial (RTC), in which subjects are arbitrarily assigned to participate in either the test group or a control group. That standard is simple to uphold if you’re observing inanimate objects, but has presented a major challenge in the study of human beings. A researcher who wants to understand whether, for example, a toddler’s exposure to books affects his or her future chances of employment cannot ethically prevent a group of kids from learning to read. 

Why is why historically much of the research on how on an individual is shaped has focused on nurture, “the relative importance of a multitude of environmental factors,” while ignoring what Fletcher calls the “black box” of nature. He is attempting to unlock that box by using genes as instruments to create better experiments on some of the most confounding and important questions in the social sciences, such as whether your health influences your ability to learn.

Fletcher’s work could have implications for the way policy-makers look at both individual achievement and the entire education system. He analyzes DNA samples from pairs of siblings in hopes of finding a causal link between specific health conditions (i.e. ADHD, obesity) and social outcomes. Each sibling in a family is essentially an entry in the genetic lottery. They may get a specific trait from a parent or they may not, providing the “50/50, flip-of-a-coin probability” that is the hallmark of the RTC.

A British epidemiologist has used a similar method to determine whether alcohol is the cause of certain diseases. Daniel Benjamin, a behavioral economist at Cornell, explains:

Since alcohol consumption is correlated with having these diseases, epidemiologists have long suspected a causal effect of alcohol consumption on the likelihood of getting these diseases, but it has been hard to prove because the correlation may be due to a common third factor. Perhaps these are people who just don’t take care of themselves… Using genetic data in this way, George and his co-authors have argued that that the effect of alcohol consumption is indeed causal.

What’s the Significance?

As genetic information becomes cheaper and more available, the elegant mechanisms of the body can be used to revolutionize more than medicine. “Mostly what people have imagined using genetics for is finding the genetic causes of disease, ” says Benjamin. But with the cost of genotyping falling at a rate faster than Moore’s Law, genetics could be used to answer questions that have nothing to do with genetics. Many of those questions may just be too complex for this method to be relevant, according to Benjamin, but the idea has the potential to explode the field.