Sunday, May 22, 2022

DNA Numbers

We have new DNA updates that break down which parent our ethnic mixes come from.  Fun.  With us, there are not only the two of us but our Romanian sons and our nephew/son whose mother was 50% Jewish (now pretty clearly Russian Jewish according to the 1950 Census.) So even though my wife and I are descended from the coasts of That Giant Lake That Is The North Sea (plus some Irishmen), we gradually added in variety.  And JA adding in a wife from the Philippines makes us now outrageously varied, The numbers are clearly wrong in some spots, but perhaps a bit closer than the last updating.  Whether they will be able to trace another step back and differentiate my grandparents is unknown to me at present. Yet how can the numbers be that wrong? I have a 100% Swedish grandmother.  That's 25% for me.  So how do I get a number of 36%? Sure the East Anglians or the Scots might have brought in a little bit, but that's a big spread.  If you are looking at your own numbers and scratching your head, I have a little knowledge.

1. This isn't your whole genome.  This is a sampling of targeted spots which have had good value in identifying regions of origin in the past. It's likely to get better, and as whole genomes drop even lower in price - I think they are on the way to a hundred buck apiece at this point - the focus of these companies will increasingly be on interpreting this more complete data, not on finding good SNPs that can suss out whether the rumor your great grandfather was from West Yorkshire might be true or not.

2. There often isn't a lot of difference between nearby places that we think of as very separate, or necessarily a lot of similarity among places we think of as related. If ancestors were from "France" we think of them as likely to be the same, Normandy to Nice, and different from "England." But looking over 1000-3000 years ago, that is going to be deeply untrue. Where the boundaries now are and what languages people speak have interesting connections to the realities of the year 1, but thinking in those terms misleads more than enlightens. As an example, my wife's mother had both parents born in the Netherlands and was conceived there herself. (Family Story) But my wife's deeper DNA has consistently shown nothing from that area as a central focus. This new computation that identifies her mother's DNA more distinctly also shows none of it.  However, it shows all the areas around it: England, Germanic Europe, some Scandinavians and some Balts. Does this mean that her ancestors were "really" from Germany or East Anglia, not Holland?  That would be odd, because we have tracings on both sides back 400 years, all Holland. Somebody in that crew has got to be the result of persistence in the area. More likely, the identifying genes for East Anglia are also fairly common in Holland and Denmark and Saxony. might call it an English identifier because it is more common there.  But there was plenty of it in Holland also. On the coasts, people moved about and bred with a wider choice of folks.  Up in the hills people stayed in their own valleys much more.

3. You don't actually inherit 50% from each parent.  That's only the average. Most people fall between 45-55%, but there are some down to 40% and even down to 35% vs 65% is not unheard of.  So you really might have gotten a different mix from your parents than your sister did. Maybe that helps you breath a sigh of relief. 

I am also on Living DNA and one can see on both sites the same combos.  Sweden is in the batch with the top half of Denmark, those are separate from Norway, which includes Iceland. Danelaw England shares a secondary circle with Normandy and Benelux. Western Lowland Scotland bleeds down into Northern Ireland (genetically true long before the Enclosure Act), Eastern Scotland into the continent and Scandinavia and the north of England, and The Highlands are a touch distinctive right the way back.

For those with any European Jewish ancestry, the belief has always been that there is a Generic Ashkenazi, with Galician and Litwak concentrations sprinkled in.  A Chinese researcher looking at one of the million-sample experiments detected that there are in fact only two - the Litvak (think Lithuania) is quite distinct, but the Galician (think Transylvania/Hungary/Slovakia) DNA  turns out to be indistinguishable from "all the rest."  It's now Litvak vs All Others.


Ganzir said...

My AncestryDNA origins breakdown:

Norway 30%
England & Northwestern Europe 28%
Scotland 15%
Sweden & Denmark 9%
Ireland 8%
Wales 8%
European Jewish 1%
Indigenous Americas-North 1%

I question how reliably the countries of the British Isles can be differentiated, especially considering that I have plenty of Irish ancestors and no known Welsh ones, but there you go. Also, one of my sixth-great-grandmothers was the daughter of a Creek tribal chief (Efau Haujo), making me 1/256 Native American Indian 'by blood', so the 1% is an overestimate, presumably because Ancestry doesn't report with greater than percent precision.

Assistant Village Idiot said...

I think you are interpreting off approximate data pretty exactly. A lot of Welshmen moved to Scotland in the First Millennia, apparently. The name "Wallace" means Welsh man, and they seemed to have been accepted quite readily. It's the Other Celtic Group, and the deep mix is hard to suss out. Though there are Other Other Celtic groups of Manx and Bretons, just for openers.

For the rest, there's a fair bit of Lake North Sea there. Even Norway, which might theoretically extend up as far as the Lofoten Islands (fish trading for centuries), is going to be mostly Stavnger, Bergen, Oslo, Gothenberg. You could call some of the Scandinavian bits Baltic Sea if you preferred, but there was just coastal movement and raiding for centuries there.

Ganzir said...

I should have clarified that I didn't believe those approximate data to be precise or even close to it. For one thing, I have only one Scandinavian (Norwegian) great-grandparent, so I should be ~12.5% Scandinavian 'by blood', which leaves an extra 25% unaccounted for between Norway and SweDenmark. Then again, I'm largely Irish, and Vikings spread their genes in that area...

What do you mean by Lake North Sea? This? :

Also, re: your observation that 50% inheritance from each parent is only the average. I thought the way it worked is that you get one chromosome from each parent in each pair, but each of those chromosomes is mixed from the donating parent's chromosomes. In that case, you would necessarily get half your genome from one and half from the other, but you could have not precisely a quarter from any given grandparent, not precisely an eighth from any given great-grandparent, etc. This does not account for chromosomal disorders or overlap (and don't all or almost all humans share most of their DNA anyway)?

Assistant Village Idiot said...

Yes, that is what I name Lake North Sea with a chuckle. I have wondered whbether teaching European (and other) history by focusing on the interactions between cities, regions, and tribes in an area around such bodies of water - land transportation was very difficult in most places - intentionally disregarding what we now call the countries the supposedly belong to, would be a better way to understand human history. If JMSmith is still reading, perhaps he will weigh in. It's his field.

Assistant Village Idiot said...

As for the DNA, we inherit from both equally, but what is expressed can turn crazy on us. Because SNPs show up in chains rather than 50-50 at every point, and those chains are often working as a unit, we get concentrations. I recommend Razib Khan on the topic, who is way smarter and more informed than I. Plus he has great guests.