Does this make sense?

[Glen in Tinsel Kni]

My estimates on four sites are so different that on the figures alone you would assume they were from four different testers.  I range from 15% English up to 70% and zero Irish up to 55% depending which site is viewed. Based on my matches, or lack of, I'd be more inclined to believe my ancestors are from Mars. 

[phil57]

It's important to recognise the difference between ethnicity regions and communities as far as Ancestry are concerned. Ethnicity region estimates are derived from your DNA test and the aim is to match your DNA to regions where it can most commonly be found in current populations, via the reference panels that Ancestry use to identify those regions. It is meant to indicate connections from more than 500 to several thousand years ago, so further back than the majority of traditional family tree research will have taken most people. A match does not necessarily indicate that your ancestors came from that region, only that people who currently live in that region supposedly have similar regional markers in their DNA.

Scotland is a good example, and Ancestry have a specific explanation for it. If you have been allocated any Scottish ethnicity, you can click on the link "Surprised by your Scotland result?" to read all about it. It does not necessarily mean that you have ancestors who came from Scotland. What Ancestry determine as Scottish ethnicity is most commonly currently found in the region they identify as Scotland, but their Scottish ethnicity is also widely found in England and Ireland amongst people who have no known connection to Scotland, probably because the people with that ethnicity all originally derived from the same location in i.e. NW Europe and travelled to various parts of the UK - perhaps most commonly to Scotland, but also many of them who travelled directly to England or Ireland and settled there without ever having set a foot in Scotland at all.

Ancestry's communities are derived differently. As well as a partial regional ethnicity aspect derived from your and other members DNA tests, they scour the trees of those people who have similar ethnicity and who are genetically familial DNA matches (cousins) to identify common locations (communities) in those trees where your and your DNA cousins ancestors can be found. In that way, they claim to identify common regions where your ancestors were found within the last 500 years; i.e. within the scope of documented genealogical research and therefore apparent in the information found in matches' family trees. Via that information, communities can be identified with some accuracy, but they can also be inaccurate. A case in point being two communities in the USA to which I have no direct ancestral connection whatsoever, but which Ancestry had allocated to me because a very large number of my DNA matching half cousins are to be found there as a result of several offspring of my GGF and one of his previous wives prior to his marriage to my GGM having emigrated their and bred profusely. Neither I or any of my direct ancestral line have ever been resident in the USA within the last several hundred years, although indirect cousins on several family lines did emigrate there as well as to Canada, Australia, South Africa and South America. Interestingly, those communities now seem to have been removed from my latest update.

[Stanwix England]

Ancestry seems to have made some change to the way that the calculate ethnicity recently since the update, and a lot of people who are from the UK suddenly have more Welsh, or some Welsh when they had none.

Before the update, I had no Welsh. Now I have 5%

My parents just got tested so they are in the 'new' batch. Neither of them has enough Welsh to account for me having 5% - yet we are a DNA match as expected.

On neither tree branch have I been able to find any link to Wales. No obvious DNA matches to Welsh people either.

Realistically, the idea that we can draw border lines between English, Welsh and Scottish DNA has always been a little bit of a stretch in my view.

I suspect that my Welsh DNA is possible just English or Irish DNA mislabelled.

[coombs]

My great grandfather came from Northern England. Co Durham. Further back he had ancestors from North Yorkshire, Cumbria and Southern Scotland. So I would not be surprised if I found my DNA estimates had a chunk of what is known as Scottish DNA.

My East End ancestors born in the 1830s was of mainly Huguenot descent, one of them one of the last to come to the UK in 1752 from Western France. Poitou to be exact. Poitou is an area which should have a lot of Celtic DNA or some Gallo-Roman apparently.

[Ruskie]

Your reply at #10 is excellent Phil. You always explain things well. 

Can I just ask you one thing? You said “…. It is meant to indicate connections from more than 500 to several thousand years ago …”

I read on a couple of that autosomal DNA only goes back from four to eight generations, though I’ve read threads here which say it can be a lot further.

(I know that Y-DNA and mtDNA can be passed down many thousands of years.)

[phil57]

I'll have a stab at an answer Ruskie, but I don't understand it all in any detail either.

However, segments of DNA inherited through family relationships become watered down (for want of a better term) over generations, and can either disappear completely or become so small as to just become random noise after several generations due to both the randomness of inheritance and the addition of segments inherited from subsequent descendants of more distant ancestors in your line and their spouses or partners etc.

The ethnicity reference panels chosen by Ancestry and other companies are supposedly identified in part by evidence or belief that their families have been present in a particular region for many generations. When each Ancestry test is examined for ethnicity, rather than looking for segments inherited by family relationships, the full sample is split into segments that are each examined for evidence of what are considered to be regional inheritance patterns - believed to be common to general populations rather than only passed down through specific family lines by relationship inheritance. When I say that they are not looking for segments inherited by family relationships, that's not strictly true, as Ancestry at least use a process which attempts to identify those segments and actually strip them out of the ethnicity calculation.

It's a lot more complicated than that, but they aim to identify regional similarities in the split segments that have been passed down through populations living in those locations and which remain pretty much unchanged over a longer period of time than the reach of family inheritance alone.

The results are probabilities, not guaranteed facts. When they assign a particular string found in your or my DNA to a region, they believe it matches that region to the highest probability of what may be several or even numerous indicative matches to different regions entirely. They aim to achieve an overall accuracy of more than about 80%, but for some regions the accuracy may be only 50% or lower.

There is an interesting and even better explanation of Scottish ethnicity by way of an example in Ancestry's white paper:

"For example, in Figure 4.4 there is assignment to the Scotland region in the Brittany area of France. This makes sense because of shared Celtic ancestry in both Scotland and Brittany, where the Celtic language Breton is traditionally spoken. Scotland estimates in England also likely reflect the history of Celtic ancestry in that area."

In other words, an ethnicity allocation to Scotland may not have any connection to the country of Scotland at all, but could relate to the fact that your ancestors came from Brittany in France and settled in England. I have an allocation of 8% Scottish ancestry in my ethnicity estimate, which derives from a probability of 0% to 25%. In other words, Ancestry are saying that it's possible despite the 8% allocation that I might have no Scottish ethnicity at all. Certainly, I have no known line of direct descent to Scotland, but I do know that both my mother's and father's surnames are believed to derive from names that originated around the Brittany/Normandy border region.

But does that account for my Scottish ethnicity allocation, or is that purely expectation bias on my part, in trying to justify an allocation that may not in fact even exist?

[SMJ]

Possible scenario to explain unexpected country connections

Two brothers several generations ago move to different countries and have families of their own. Brother 1 stays at his place of birth - say Shropshire. Brother 2 moves away, say Belfast. Later on, descendants of both of the brothers take DNA tests.

The results will then be picked up by the DNA sites and various algorithms used to guesstimate matches. You would expect Brother 1 to show connections to the country of Brother 2 and visa versa.

Things could get more complicated if Brother 2 moves back home after separating from his family who are left in Ulster contributing to the gene pool.

Brother 1 has never visited or lived in Ulster yet the data will be presented to the descendants of Brother 1 as though they are n% Ulster Irish.

The correct interpretation should be ’n% of Ulster people share the same DNA as Brother 1’s descendant’ a completely different argument from a logical point of view and entirely correct, but not so easy to sell.

My own matches show 18% NI & SW Scotland, but I have no paper evidence to back this up. Also, I only have 2% South Wales Borders and 2.4% North Wales. My 2xGtGf was born in Wales and his descendants, partners and myself were born less than 10 miles from the Welsh Border scattered in Flintshire, Denbighshire & Shropshire. If I was looking at this objectively from the DNA evidence, I would conclude I had very little, if any, ancestral connection with Wales and Shropshire which is of course false.

I'm guessing the dataset for the Welsh Borders is small at the moment and as a consequence the algorithms go for a nearest fit with the much larger dataset of emigre Scots and Irish appearing in the DNA tests from N America and Australasia. They often have well documented paperwork links back to the British Isles too to provide the connection.

[DianaCanada]

Very interesting replies, and thank you all for your input. 
One more strange point re my “Scottish” ancestry, it shows more of it coming from my Sussex mother,  for both my brother and me, and I mentioned the paper trail and the DNA matches all agree with a deep Sussex ancestry.  Not a Scot in sight!

[Ruskie]

Phil.

Many thanks for your excellent interpretation. You claim to not understand it - maybe that is why you explain things so clearly, as you keep it quite simple.

I don’t know if any of the companies are continuing to expand their sample populations, so this may have changed, but some of the sample populations used to be quite small, and for some regions of the world were in the single figures. I had a (now lost) document some years ago which listed the numbers (I know Ancestry have a list of their own). Despite the low numbers, if there was not much movement in these remote areas I suppose it is possible that these are more representative/‘accurate’ than the larger samples in more populated regions where there was more movement of people in and out.

Interesting to mull over.