There are many factors that shape and influence our political views; our upbringing, career, perhaps our friends and partners. But for a few years there’s been growing body of evidence to suggest that there could be a more fundamental factor behind our choices: political views could be influenced by our genes.

The idea that political views have a genetic component is now widely accepted – or at least widely accepted enough to become a field of study with its own name: genopolitics. This began with a pivotal study, which showed that identical twins shared more similar political opinions than fraternal twins. It suggested that political opinion isn't just influenced by dinner table conversation (which both kinds of twins share), but through parents' genes (which identical twins have more in common than fraternal twins). The strongest finding from this field is that the position people occupy on a scale from liberal to conservative is heritable. The finding is surprisingly strong, allowing us to use genetic information to predict variations in political opinion on this scale more reliably than we can use genetic information to predict, say, longevity, or alcoholism.

Does this mean we can give up on elections soon, and just have people send in their saliva samples? Not quite, and this highlights a more general issue with regards to seeking genetic roots behind every aspect of our minds and bodies.

Since we first saw the map of the human genome over ten years ago, it might have seemed like we were poised to decode everything about human life. And through military-grade statistics and massive studies of how traits are shared between relatives, biologists are finding more and more genetic markers for our appearance, health and our personalities.

But there's a problem – there simply isn't enough information in the human genome to tell us everything. An individual human has only around 20,000 genes, slightly less than wild rice. This means there is about the same amount of information in your DNA as there is in eight tracks on your mp3 player. What forms the rest of your body and behaviour is the result of a complex unfolding of interactions among your genes, the proteins they create, and the environment.

In other words, when we talk about genes predicting political opinion, it doesn't mean we can find a gene for voting behaviour – nor one for something like dyslexia or any other behaviour, for that matter. Leaving aside the fact that the studies measured “political beliefs” using an extremely simple scale, one that will give people with very different beliefs the same score, let's focus on what it really means to say that genes can predict scoring on this scale.

Getting emotional

Obviously there isn't a gene controlling how people answer questions about their political belief. That would be ridiculous, and require us to assume that somewhere, lurking in the genome, was a gene that lay dormant for millions of years until political scientists invented questionnaire studies. Extremely unlikely.

But let’s not stop there. It isn't really any more plausible to imagine a gene for voting for liberal rather than conservative political candidates. How could such a gene evolve before the invention of democracy? What would it do before voting became a common behaviour?

The limited amount of information in the genome means that it will be rare to talk of "genes for X", where X is a specific, complex outcome. Yes, some simple traits – like eye colour – are directly controlled by a small number of genes. But most things we're interested in measuring about everyday life – for instance, political opinions, other personality traits or common health conditions – have no sole genetic cause. The strength of the link between genetics and the liberal-conservative scale suggests that something more fundamental is being influenced by the genes, something that in turn influences political beliefs.

One candidate could be brain systems controlling our emotional responses. For instance, a study showed that American volunteers who started to sweat most when they heard a sudden noise were also more likely to support capital punishment and the Iraq War. This implies that people whose basic emotional responses to threats are more pronounced end up developing a constellation of more right-wing political opinions. Another study, this time in Britain, showed differences in brain structure between liberals and conservatives – with the amygdala, a part of the brain that learns emotional responses, being larger in conservatives. Again, this suggests that differences in political beliefs might arise from differences in emotional processes.

But notice that there isn’t any suggestion that the political opinions are directly controlled by biology. Rather, the political opinions are believed to develop differently in people with different basic biology. Something like the size of a particular brain area is influenced by our genes, but the pathway from our DNA to an apparently simple variation in a brain region is one with many twists, turns and opportunities for other genes and accidents of history to intervene on.

So the idea that genes can have some influence on political views shouldn't be shocking – it would be weird if there wasn't some form of genetic influence. But rather than being the end of the story, it just deepens the mystery of how our biology and our ideas interact.

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