“Why I regret using 23andMe: I gave up my DNA just to find out I’m British” – The Guardian, 2 Dec 2024
December 11, 2024
This headline appeared in The Guardian early last week and it raises some interesting questions. The journalist in question, Kari Paul, is an American now based in Paris, who wrote as a technology reporter. The basic thrust of the article is that 23andMe told her she was 63% British and Irish, 17% Danish and otherwise “broadly north-western European”. This was not a surprise – in fact, it was rather more boring than she was hoping – and given the fact that she passed her sensitive genetic information to a private company in exchange for that knowledge, I can see why she’s a bit miffed.
What I don’t understand, though, is the background to that miffed-ness.
At a very high level, autosomal DNA can be a numbers game as illustrated through the Punnett squares we are taught in GCSE Biology. Everyone inherits 50% of the DNA from their father, and the other 50% from their mother. They each inherited 50% of their DNA from each parent, and so on up the tree.
The article mentions that her father’s family have maintained meticulous family records linking them directly to the Irish village they emigrated from. That kind of information is invaluable within a family, and she is very lucky to have it. Taking for a moment the broad assumption that her Irish ancestors married within their community in the USA, which is not a wild conjecture, we can posit that 50% of her DNA was going to be Irish anyway. So that dispenses with half the issue.
Her mother’s family have not kept records, but she knows that her grandmother’s great-grandparents (so, her three-times great grandparents, five generations back, covering a period of likely anything between 100 and 200 years, depending on generation sizes) were Danish and spoke little to no English after they arrived in the USA. This makes it likely they emigrated as the heads of a family of up to three generations, and held onto their own language and culture.
Let us therefore sketch-in a maternal family tree of six generations ending at the writer. Great-great-great grandparents emigrate to America with adult children who either also bring children with them, or marry within the new Danish-American community. That makes the family fully Danish to great-grandparent level, when viewed from the writer’s point of view. At the point, the family start marrying non-Danes, but probably immigrants who share similar cultures to themselves – Dutch, German, English, Irish, other Scandinavians. The Danish genes therefore halve with each generation until the writer herself inherits only 18.75% Danish genes, which is close to what the report shows. The rest of her DNA is North West European, which ties exactly to people marrying within familiar, if not identical, cultures and traditions.
What this means, then, is not only that ten minutes with a pencil and paper would have made this obvious; but also that a little bit of personal family tree research would go a long way. If family memory holds the Danishness at 3x great grandparent level, it almost certainly holds some names or locations which would make research easier.
I do understand that there is disappointment that it did not prove a family story that there was some Czech heritage; but that still doesn’t mean it wasn’t there. Although Ms Paul might have been hoping for Slavic genes, it appears that the Czech people are actually descended from pre-Slavic Western and Central European nomads and warriors from Bavaria and Poland.[1] This is backed up by a quick Google of her family’s surname, Galusha, which suggests it is either an anglicised Polish name (Gałusza), or taken from the Celtic “Gallus” meaning “stranger” (although that is repeated with confidence by a number of people with no etymology to back it up. “Celtic” is a bit broad as a language descriptor!).
Even though I do a lot of genealogy, I agree with Ms Paul’s ethical and privacy concerns about giving her genetic data (and that of her family members, by extension) to a private company and where it might end up. I’ve not done my own DNA history on that basis. But it could all have been avoided anyway if she’d just asked the right questions.
[1] Beneš, Dr Jaromír, head of the Laboratory for Paleoethnobotany and Paleoecology at the University of Southern Bohemia, speaking to Czech Radio in July 2019 – https://english.radio.cz/czechs-are-predominantly-descendants-pre-slavic-populations-says-archaeogenetics-8124928 accessed 11 December 2024