Which is more accurate AncestryDNA or 23andMe?

I've been researching my ancestry, on and off, for about 30 years. That included interviewing elderly relatives, family histories, photographs, documents, etc. It progressed onto BMD certificates, Census, and many, many visits to local record offices, churches, and archives across Britain in order to examine parish registers, transcripts, minute books, etc.

These days I have the luxury of online genealogical resources, and the ability of searching online data bases. To cut a long story short, I have accumulated a family history that includes the names of 279 recorded, direct ancestors, 277, of which lived in South East England, particularly in the East Anglian County of Norfolk (the other two were a Swiss 3 x great grandparent and his named father).

At Generation 6 (3 x great grandparent), I can say that on paper, I am 97% South East English (including 75% East Anglian), and 3% Swiss. In other words, pretty much of local East Anglian ancestry. Here is a map showing my recorded ancestors - blue via my father (minus the few in Switzerland), red via my mother:

Okay, I will still have some mistakes in my genealogical research, particularly on more distant lines, where records start to be come more scarce and have less survival. There would also be some NPEs (non parental events). However, if I compare my pedigree with DNA matches / cousins that share common ancestors both in segments and on paper trails, I get this (shaded areas verified with DNA matches to paper trails):
So there is a reasonable verification there.

That is my background. The results? Remember, Generation 6:

97% English
3% Swiss

Well before phasing, 23andme gave me:

100% European: 94% NW European. 3% Southern European. 3% Broadly European. Broken down to:
32% British & Irish
27% French & German
7% Scandinavian
29% Broadly NW European
2% Broadly Southern European (including 0.5% Iberian)

After phasing with a surviving parent, it adjusted to:

100% European: 96% NW European. 2% Southern European. 2% Broadly European.
38% British & Irish (23% from father, 15% from mother)
24% French & German (13% from father, 11% from mother)
0.8% Scandinavian (from mother alone)
34% Broadly NW European (22% from father, 12% from mother)
2% Broadly Southern European (1% from father, 1% from mother)

Not very impressive is it?

AncestryDNA gave me:



Still way off, but a lot closer and more precise than 23andme. They also assigned me both to the Southern England Genetic Community, and to the East Anglia & Essex Genetic Community, perfectly correct.

Therefore in summary - I've come to the conclusion that NO current autosomal DNA test for ancestry is capable of accurately predicting your ancestry below a very large region, such as NW Europe - unless your ancestors belong to a particularly well defined population that avoided medieval admixture. They are all inaccurate. More important to me now is that they have fat databases of testers, with a system of searching them alongside family trees, ancestor locations and surnames. However, side by side - for my results, and weighed simply against recorded family history, I have to pronounce AncestryDNA/.com to be more accurate than 23andme.

Will ancestry DNA tests tell me my family origins?

I have taken several DNA tests for ancestry, including those provided by the FT-DNA, 23andMe, and Living DNA companies.  Unusual for a tester, I am actually of a single population, very local, well documented ancestry here in East Anglia, South-East England.  I'm not someone in the Americas or Australia, that might have very little clue what parts of the world that their ancestors lived in, previous to immigration.  I know my roots, I'm lucky.  I live them.  You might ask, why did I feel the need to test DNA for ancestry?  The answer is, curiosity, to test the documented evidence, fill the gaps, look for surprises, and in particular, to understand the longer term, to reach further back into my ancestry.

I have though, become a bit of a skeptic, even a critic, of autosomal DNA (auDNA) tests for ancestry.  They are the tests presented by the businesses in results called something like Ancestry, Family Ancestry, Origins, Family, Composition, etc.  Instead of testing the haplogroups on either the direct paternal (Y-DNA), or direct maternal (mtDNA), these tests scan the autosomal and X chromosomes.  That's good, because that is where all of the real business is, what makes you an individual.  However, it is subject to a phenomena that we call genetic recombination (the X chromosome is a little more complicated).  This means that every generation circa 50% of both parents DNA is randomly inherited from each parent.  I said randomly.  Each generation, that randomness chops up the inherited segments smaller, and moves them around.  After about seven or eight generations, the chances of inheriting any DNA from any particular ancestral line quickly diminishes.  It becomes washed out by genetic recombination.

Therefore, not only are the autosomes subject to a randomness, and genetic recombination - they are only useful for assessing family admixture only over the past three hundred years or so.  There is arguably, DNA that has been shared between populations much further back, that we call background population admixture.  It survived, because it entered many lines, for many families, following for example, a major ancient migration event.  If this phenomena is accepted - it can only cause more problems and confusion, because it can fool results into suggesting more recent family admixture - e.g. that a great grandparent in an American family must have been Scandinavian, when in fact many Scandinavians may have settled another part of Europe, and admixed with that ancestral population, more than one thousand years ago.

DNA businesses compare segments of auDNA, against those in a number of modern day reference populations or data sets from around the world.  They look for what segments are similar to these World populations, and then try to project, what percentages of your DNA is shared or similar to these other populations.  Therefore:

  1. Your results will depend on the quality and choice of geographic boundary, allocated to any reference population data set.  A number of distinct populations of different ancestry and ethnicity may exist with in them, and cross the boundaries into other data sets.  How well are the samples chosen? Do they include urban people (that tend to have more admixture and mobility than many rural people).  Do they include descendants of migrants that merely claim a certain ancestry previous to migration?What was the criteria for sample selection?
  2. Your results might be confused by background population admixture.
  3. You are testing against modern day populations, not those of your ancestors 300 - 500 years ago.  People may well have moved around since then.  In some parts of the World, they certainly have!

It is far truer to say that your auDNA test results reflect shared DNA with modern population data sets, rather than to claim descent from them.  For example, 10% Finnish simply means that you appear to share similar DNA with a number of people that were hopefully sampled in Finland (and hopefully not just claim Finnish ancestry) - not that 10% of your ancestors came from Finland.  That is, for the above reasons, presumptuous.  It might indeed suggest some Finnish ancestry, but this is where many people go wrong, it does not prove ancestry from anywhere.

Truth

This is my main quibble.  So many testers take their autosomal (for Family/Ancestry) DNA test results to be infallible truths.  They are NOT.  White papers do not make a test and analysis system perfect and proven as accurate.  Regarding something as Science does not make it unquestionable - quite the opposite.  The fact of the matter is, if you test with different companies, different siblings, add phasing, you receive different ancestry results.  Therefore which result is true and unquestionable?

A Tool for further investigation

So what use is DNA testing for ancestry?  Actually, I would say, lots of use.  If you take the results with a pinch of salt, test with different companies, then it can help point you in a direction.  Never however take autosomal results as infallible.  Critical is to test with companies with well thought out, high quality reference data sets.  Also to test with companies that intend to progress and improve their analysis and your results.

For DNA relative matching, then sure, the companies with the best matching system, the largest match (contactable customer) databases, and with custom in the regions of the world that you hope to match with. There is also, GEDmatch.  Personally, I find it thrilling when I match through DNA, but in truth, I had more genealogical success back in the days when genealogists posted their surname interests in printed magazines and directories. 

The results of each ancestry test should be taken as a clue.  Look at the results of testers with more proven documented and known genealogies.  Learn to recognise what might be population background, as opposed to recent admixture in a family.  Investigate haplogroup DNA - it has a relative truth, although over a much longer time, and wider area.  Just be aware that your haplogroup/s represent only one or two lines of descent - your ancestry over the past few thousand years may not be well represented by a haplogroup.  Investigate everything.  Enjoy the journey.  Explore World History.

So which is it?

Following on from my last two posts.  Simple.

  1. The DNA companies are correct in their assessment of my ancestry.  I have Southern European Ancestry within the past 500 years.  Perhaps Iberian, perhaps Balkan?  Maybe via both my father and mother?
  2. The Southern European picked up by atDNA tests for ancestry, relate to ancient patterns, shared by the English.  They could be Neolithic, or other Late Prehistoric.  They could be Roman.
  3. Commercial autosome DNA Tests for Ancestry fail.  There is no Southern European, neither within the past 500 years, nor ancient.  It's all bogus.  Current chips and references fail to differentiate successfully between European populations of the past.

So which one is it? I'll be looking at answering this in my next few posts.