That’s a map from one of the commercial DNA testing companies showing my ancestry– half East Asian, almost half British, with a little Finnish and Central Asian. The test pretty much confirms what I already knew about my parents’ backgrounds, though the Finnish is a bit of a mystery (and probably something more like a statistical error or algorithmic equivalent of a best guess).

For those of us who’ve had these tests done will appreciate Kristen Brown’s latest article in Gizmodo, “How DNA Testing Botched My Family’s Heritage, and Probably Yours, Too:”

A big problem is that many of us have a basic misunderstanding of what exactly we’re reading when Ancestry or 23andMe or National Geographic sends us colorful infographics about how British or Irish or Scandinavian we are. It’s not that the science is bad. It’s that it’s inherently imperfect, an estimation based on how much our DNA matches up with people in other places around the world….

Heritage DNA tests are more accurate for some groups of people than others, depending how many people with similar DNA to yours have already taken their test…. That the data sets are primarily made up of paying customers also skews demographics. If there’s only a small number of Middle Eastern DNA samples that your DNA has been matched against, it’s less likely you’ll get a strong Middle Eastern match.

I assume that these tests haven’t been as popular with people of East Asian descent, because my dad’s family is pretty clearly been in northern Korea and Manchuria for a few centuries (with some Mongolian ancestors mixed in), and I can’t imagine that the two billion people between Srednekolymsk and Singapore are that genetically similar. So presumably as more people in and from Asia take the test, that giant green blob will get smaller.

And indeed, it turns out, as the databases grow, the places they tell you you’re from change:

Another anecdote that stuck with me came from my friend Alexis Madrigal. Initially, he said, his Mexican family came up as Arab North African, which was surprising. As 23andMe refined its test and its data set grew, it also refined the results: Now, he was descended from Jewish people from Southern Europe. The number of Madrigals in central Spain had long led the family to suspect that their migratory path to Mexico had at some point passed through this region. As more people took the test, the picture of where his family was “from” changed. The Canadian bioethicist Timothy Caulfield shared a similar story. At first a DNA test revealed he was entirely Irish, but as the data set changed, he gradually became less Irish.

It’s an interesting piece, and it raises some good questions about why we even bother with this kind of thing in, as she puts it, “in a world where people have been mixing and matching and getting it on since the beginning of human history.”