I have a grandfather Logsdon, a grandfather Harvey, a grandmother Patterson, and another grandmother who was a bit of a black sheep. Her name was “Per-vet”; that is how I’ve heard it pronounced, but I never met her and I’ve never seen it written down.

According to a document sent to me as junk mail by a company which wanted to sell me a plaque, Logsdon is an English name, derived from Longsdown, meaning a long hill. Harvey is pretty certain to be English. Patterson is supposed to be Irish, by one authority, and Scotch-Irish according to another. History will tell you that the Scotch-Irish were just Scots who went to colonize Ireland. I strongly suspect that “Per-vet”, if seen written down, would be spelled funny and would be French.

So we see that a cursory glance says I am one-half English, one fourth French, and one fourth either Scots or Irish or both. But how reliable is that?

Not very. Let’s take the name of one of my grandparents and play with the possibilities it offers. A hypothetical fellow named Patterson, from Patterson Holler, deep in Appalachia, where there are a hundred families all inter-related back nine generations, is probably safe in concluding that he is Scotch-Irish.

However, another man named Paterson(1) comes straight to America from Belfast and marries a woman named Smith. His son, Patterson(2) marries a woman named Jones, his son Patterson(3) marries a woman named Wilson, his son Patterson(4) marries a woman named Harlan. Their son, Patterson(5), will have one-sixteenth of his genetic heritage from Patterson(1). His name will be Patterson, but should we call him Scotch-Irish?

Should we call him he Scotch-Irish if the young women named Smith, Jones, Wilson, and Harlan were all visibly black women?

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Like everyone else, I’ve seen the PBS program Finding Your Roots. The team behind the scenes is impressive, but no matter how good you are in genealogy, history, or biography, there is always a limit to certainty. Documentary evidence is always suspect. People lie, clerks transpose names, and harried bureaucrats write down what they think to be true because they have to write down something. Those in charge of data are people in power, and axes get ground. The stories unearthed are sometimes fascinating, but let’s remember to take them with at least a grain of salt.

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Then we have Ancestry.com. I have no intention of criticizing their work, but their advertisements deserve a kick in the ribs.

We’ve all seen the one about the black woman with ancestry from Ghana. Lets assume that she did have an ancestor from Ghana (an assumption we make without accepting the very shaky hypothesis that genealogists can determine such a thing from a DNA sample) and that her ancestor arrived in America about 1800. That is nine generations ago. Our subject would have 256 great great great great great great great grand parents in that generation. That one of them was from Ghana tells us next to nothing. The other 255 ancestors were probably from all over Africa and Europe – just like my ancestors and yours.

There is the another ad where a white American who has believed that he is Scottish discovers after a DNA test that he is actually German. He has to trade his kilt for lederhosen.

Cute, but this holds about as much water as cheesecloth. What is it to be a German? Germany only became a country about a hundred-fifty years ago, and its borders have fluctuated widely since then.

Hitler notwithstanding, there are no genetic Germans, just folks who happen to live in a particular part of Europe, during a narrow range of years, speaking a particular language. These things leave no trace in the DNA.

Searching for ancestors can be an exercise lubricated by snake oil. While there’s nothing wrong with a little fantasy, it can lead to blindness. When I was young, everybody bragged about their lost Cherokee ancestors. Nobody bragged about their lost Black ones.