Researchers and scholars have long debated the question of “nature vs. nurture” – whether our genetics or the environment (be it natural and social) has a greater influence on our traits. Much genetics research has shown that both genes and environment shape our traits. However, several recent studies suggest that, at least for the specific traits that were looked at, the environment may play a bigger role.
In the first study, scientists in Israel focused on the microbiome, or the collection of all bacteria, in the gut. The researchers looked at Israelis with different genetic ancestries – from the Middle East, North Africa and Europe. They found that genetic differences have no significant effect on the microbiome. Then, they looked at the microbiomes of pairs of relatives who share the same household environment, those who do not share the same household, and pairs of unrelated people who share the same household. The results showed that whether individuals have similar microbiomes is affected by sharing a living environment, but not so much by genetic relatedness. Finally, the research team showed that microbiome differences have at least as great an effect as genetic variants on a number of health-related traits, such as HDL (“bad” cholesterol) levels.
In the second study, researchers in the United States obtained genealogical data from 86 million individuals, mostly in Europe and North America, from a publicly-available database. The researchers used this information to construct family trees. The largest of these contained 13 million people. Using these family trees to compare the lifespan of genetically related individuals, the scientists calculated the “heritability” of longevity to be only 16% (heritability is the measure of how much of the differences in a trait among different people is the result of genetic differences). This is significantly lower than earlier, but smaller, studies that reported a heritability of around 25%. The result points to a much larger influence by the environment on lifespan than previously thought.
Finally, in a third study, a team of Canadian geneticists studied the relative health effect of genetic ancestry vs. air pollution. They looked at residents of three different locations (both urban and rural) in the French-speaking province of Quebec. Due to the settlement history of French Canadians, the researchers were able to genetically distinguish individuals from the different geographical areas. The scientists then looked at environmental differences, specifically the local levels of air pollutants such as sulfur dioxide and ozone. They found that the environment has a much stronger effect than genetic differences on the activity levels of genes, as well as a number of health-related traits such as asthma or liver enzyme levels.
Together, these three studies remind us that genetics does not always determine our traits or health. Genetic variants obviously have some degree of influence on traits such as how long we live, or whether we develop certain diseases. But it is important to remember that the environment that we live in can have significant, and sometimes even more important, roles to play – whether by directly affecting the trait, by influencing the microbes that live in us, or by changing how our genes function.