People spend their lives trying to figure out the key to happiness, and with many economists attempting to measure well-being, even cities and nations increasingly compete over who has the “happiest” citizens.

Now a new study claims to have potentially solved a famous puzzle in social science: Why some nations are always so damn happy.

The secret? Be Danish. Or at least be not-so-distantly related to one.

Americans think it’s normal to hate their jobs. Let us introduce you to the Danish concept of arbejdsglæde. It means happiness at work. Here’s how Danish offices make sure it’s happening. Read more: 5 Simple Office Policies That Make Danish Workers Way More Happy Than Americans.

Denmark consistently tops national happiness rankings, including this year’s United Nations World Happiness report. That report measured many factors that you’d think would go into making one nation, as a whole, happier than another: GDP, “having someone to count on,” “perceived freedom to make life choices,” and more. These are all things that Denmark, a rich, progressive country with generous social welfare and workplaces policies, has in spades.

But the new research, presented in a working paper from two economists at the University of Warwick’s Center for Competitive Advantage in the Global Economy, indicates there could be another factor at play that no individual, let alone a government, has control over: genetics.

They found that the closer a nation’s genetic makeup is to Denmark, the happier the country is.

That sounds pretty surprising, and indeed the authors, Eugenio Proto and Andrew Oswald, were quite surprised by their own results. They went into the work thinking a genetic link to be “implausible.” But after finding three different lines of evidence that pointed to the role of genetics, they have reason to believe genetic patterns will help researchers understand variations in international well-being levels.