My father’s parents were both 100% Italian, which makes him what?

One hundred percent Italian.

Which makes me half Italian. Which makes my children a quarter.

My DNA test, done by Ancestry, says I am 37 to 40% Italian, and my middle son’s test says he is only 9%.

My boy was concerned about this. Only 9%? And the test says he is more Greek (11%) than Italian.

In last week’s column, I said that many people are shocked by their test results because genetics and genealogy are two very different things, and human genetic inheritance is enormously complex. That was a kind, but unsatisfying answer.

This week, I will be more forthright. DNA testing is junk science. Or perhaps a better term would be entertainment science.

Call it what you will, DNA testing is guesswork, and the results are about as trustworthy as answers from a Magic Eight Ball. On the internet, there are instances of identical twins (identical triplets, even) receiving non-matching results.

Here’s how it works – or rather, doesn’t work:

You spit into a tube or swab your cheek and send it off to a lab.

The lab extracts your DNA from the sample and ignores most of it. This makes sense because 99 percent of your DNA is identical to that of everyone else on the planet. Of the more than three billion pieces of information in your DNA, only 1%, or about three million pieces, makes you an individual.

The lab ignores most of that 1%, focusing on around 700,000 markers that they compare with those same markers in their database. The markers in their database are from people in various parts of the world who are longtime residents of certain countries, with parents and grandparents who have lived in the same area.

A computer compares your markers to those of people in the database and tries to find matches. Some of your markers may match (somewhat) those of people in one area, some may match (somewhat) people in another, and so on. The computer uses these semi-matches to guess where in the world parts of your DNA came from.

It appears very science-like – there are labs and beakers and centrifuges and computers and people in white coats, oh my – but the results are often laughable. It is guesswork masquerading as precision. It is entertainment dressed up as science. It is, as I said, junk.

DNA testing has become a big business. It is a fad that is sweeping the world. It is being advertised as the way to unlock the secrets of your lineage, to show where your people came from. My advice is this: spit in a tube and pay the fee if you want to be entertained. Don’t do it if you are looking for serious answers about your heritage. The results, rather than pointing you in the right direction, could lead you far astray.

Want to know where your people came from? Focus on your genealogy.

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