There’s a Serbian proverb that says: “You can cut off a dog’s tail, but it’s still a dog.”

It means that things have a nature that aren’t altered by outward circumstances. It’s kind of a slightly more violent Balkan version of “a leopard can’t change its spots.”

It’s an idea that’s been around for a long time: That groups of people are fundamentally different, and individuals can’t shed the group characteristics they inherit. It’s the theory behind nationalism and xenophobia. In a slightly scienced-up version, it’s also behind the DNA kits that analyze your spit and promise to tell you something about yourself.

This Christmas season, I got to take a peek into my genetic code.

Before I tell you what I saw, I have to make a couple of disclosures.

One is that it wasn’t my DNA that we tested – it was my sister’s. We had the same mother and father, but our DNA is not the same (we are siblings, not clones).

And if you are reading this hoping for one of those blockbuster discovery columns, where the author finds out that his mother has been lying to him for his whole life, you can stop now. The report told us pretty much what we already knew. But I was more interested in what it got wrong.

We are 100 percent European. Our mother’s ancestors came from England and our father’s from the Balkans, most likely modern-day Bosnia. There’s a slight possibility of some other nationalities in the mix – maybe a little French and German on my mother’s side, maybe a little Polish or Greek on my dad’s – but no big surprises.

On our mother’s side, according to the report, the English roots are so strong that my sister likely has a grandparent or great-grandparent from England. But my mother’s ancestors were Puritan colonists who came to American before the Revolution and had the habit of writing everything down. If there had been even a great-great-grandparent from England, it would have been a big deal, and we would have heard of it.

On my father’s side, the DNA test tells us that my father is most likely Bosnian or Croatian, but he’s not. His family was Serbian, which might sound like it’s close enough from here in America, but in that part of the world, it’s a really big deal. These scientists have obviously never cut off a dog’s tail.

As amazing as the technology is, the test can’t account for history.

My mother’s people were, in fact, English, but they lived in a place called New England for around 300 years. Right into modern times, they kept to themselves and married inside the group – until about 60 years ago, when my mother decided to shake up the gene pool about and marry someone “from away.”

My father was born in a village called Kesici in northwest Bosnia, on the border with Croatia. I still have second cousins who live there, and like their Croatian and Bosnian neighbors, they are the descendants of the Slavic tribes that migrated south in the sixth century A.D.

Over the last 1,000 years or so, they have lived under different flags. But their “nation” has been defined by their religion – Catholic Croatians, Bosnian Muslims, Eastern Orthodox Serbs – and not a spot on the map.

A DNA test can’t tell you the difference between a Roman Catholic and an Orthodox Christian. You would need a theologian for that. Maybe more than one.

And genes can’t tell you the difference between English people who live in Plymouth, England, and English people who live in Plymouth, Massachusetts.

The idea that you inherit your most important qualities has been around much longer than the study of genetics. Both of my parents came from very closed worlds where people who were not just like them were seen as outsiders and a threat.

If not for World War II and the mass dislocation of refugees that followed, my parents might have continued that trend.

But chance, history and love turned out to be more powerful than DNA.

And there’s not a test that measures that.

Greg Kesich is the editorial page editor. He can be contacted at:

[email protected]

Twitter: gregkesich

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