
DNA Testing Botched My Family's Heritage - anarbadalov
https://gizmodo.com/how-dna-testing-botched-my-familys-heritage-and-probab-1820932637
======
globuous
I always kinda curious about dna heritage testing. Until I saw John Sotos'
talk at Def Con 25 [0]. He highly recommands you keep your genome private. And
that you only give it away if it is vital (aka you're really sick).

The talk is absolutely amazing, probably the most captivating talk I have ever
watched (thanks HN commenter that shared it a while ago). But anyway, Sotos
specifically tells his audience that, as a security measure, they shouldn't
release their dna to heritage services. Because it isn't vital.

Anywhi, great talk, highly recommand it although Sotos mentions DNA testing
for heritage for a few seconds only, so slightly off topic :)

[0]
[https://www.youtube.com/watch?v=HKQDSgBHPfY](https://www.youtube.com/watch?v=HKQDSgBHPfY)

~~~
searine
I disagree.

Mostly for one reason alone. Genetic association testing.

To get statistical power necessary to associate variants with complex genetic
traits, we need very large sample sizes (hundreds of thousands are good,
millions of individuals are better).

If everyone clings to their genomes in fear of what bad-actors might discover,
we will never discover anything at all. Cures included.

~~~
adenadel
I also disagree. If a bad-actor wants your genetic information they just need
to go somewhere you've been. You're constantly shedding DNA.

~~~
logfromblammo
The DNA you leave behind when you touch things can actually be more useful
than just the cellular DNA isolated from a genome test and put into a
database.

DNA analysis of your microbiota can indicate more than just what you are or
who you are, but also your current health status, where you have been, and who
you associate with. It would also be one way to distinguish between identical
twins.

~~~
hartator
Identical twins have the same DNA.

~~~
onychomys
Sure, but they have different microbiomes.

------
mcguire
" _23andMe’s ancestry results were the most confounding of all. It found that
I was only 3 percent Scandanavian, a number that, based on my recent family
history, I know is flatly wrong. It also found I was only 5.5 percent Middle
Eastern and a whopping 62.6 percent Northwestern European._ "

I get how their statistical models come up with those numbers, but I have a
very hard time understanding how any reasonable person would put this much
stock in the interpretation. "3% Scandinavian?" "Flatly wrong?" Where does the
author think Scandinavia is, if not north-western Europe? Does the author
think the borders of "Scandinavia" were closed in 1000CE, with no interaction
with the rest of Europe?

~~~
Myrmornis
> Where does the author think Scandinavia is, if not north-western Europe?

Um, north-eastern Europe perhaps?

~~~
unclenoriega
If you look at the image in the article, 23andMe includes Scandinavia in
northwestern Europe.

~~~
Myrmornis
A surprising categorization by 23andMe certainly, but not one which detracts
from my post: very few people would place Scandinavia in north-western Europe
since that category implies that north-eastern Europe is an option.

~~~
klmr
> very few people would place Scandinavia in north-western Europe

Not really. I don’t presume to claim to know what “most” people think, but
placing Scandinavia in north-western Europe is hardly eccentric [1, 2].
Furthermore, its history, politics and certainly its genetics are fairly
intertwined with north-western Europe so it’s a sensible categorisation.

[1]:
[https://en.oxforddictionaries.com/definition/Scandinavia](https://en.oxforddictionaries.com/definition/Scandinavia)
[2]:
[https://en.wikipedia.org/wiki/Northwestern_Europe](https://en.wikipedia.org/wiki/Northwestern_Europe)

~~~
Myrmornis
I see, I wasn't aware that it is normal. Agree about history, politics and
human genetics (not Finland though!). I was thinking more about geography and
non-human biogeography, which support north-eastern.

------
russdill
TL;DR - Genetic tests don't give good regional ancestry results if you are
from a region that is underrepresented by genetic testing.

~~~
m0rphling
That's only partially true. The real issue is that there is no official
representation of race or heritage found in DNA. Modern genetic testing is a
best-effort exercise for classification whose 'accuracy' varies by sample
size, race coverage, and group(s) sponsoring testing/analysis.

Quite simply, one cannot look at a DNA sequence and say definitively it is one
race or another—there is no official Rosetta Stone for translating DNA to race
or heritage.

~~~
Houshalter
That's not really true. If you look at just the basic PCA of genetic data,
several races emerge very clearly and distinctly. E.g. look at this image:
[https://i.imgur.com/J2Xl2FK.png](https://i.imgur.com/J2Xl2FK.png)

I'm just guessing here, but I think the problem is they are trying to do
something more complicated than just find your nearest genetic cluster. They
want to find exactly what mix you are between different clusters. It's clear
on the graph that some people have more African ancestry than others. But what
would be an algorithm for working out the _exact_ percentage "African" someone
is? Is it euclidean distance to the median african? Or the furthest bottom
left african? Or is it just the first principle component alone?

The second problem is they don't just want 7 big clusters. People already know
they are European, they are more interested in exactly what countries/regions
they are from. And making a bunch more clusters makes the problem more
complicated.

------
loriverkutya
DNA heritage testing is often referred as genetic astorology:
[http://www.bbc.co.uk/news/science-
environment-21687013](http://www.bbc.co.uk/news/science-environment-21687013)

UCL has a nice page collecting the scientific facts:
[http://www.ucl.ac.uk/mace-lab/debunking](http://www.ucl.ac.uk/mace-
lab/debunking)

~~~
DenisM
Oh, but there is more to that. It's the kind of mysticism that the educated
people wouldn't be ashamed to engage in. The demand was there all along, and
still is, strong as ever.

Also consider magic potions, for example.

------
laurentoget
I suspect those tests have no way to work for people who come from urban
commerce centers where ethnic groups have mixed for centuries, which includes
most port city on the Mediterranean sea

~~~
carlmr
I was thinking the same. Southern Spain, Italy, Portugal and Greece and Middle
Eastern or North African will have a lot of genetic overlap.

------
patorjk
My dad had a similar experience. He's taken several different DNA tests, and
all of them give him different results. His great-grandfather apparently had
an affair with a Native American women, who had a baby but didn't want it, so
his great grandparents took the child in and raised it as their own, only
revealing the truth to him later in life.

My dad has taken several tests. One said his DNA is 10% East Asian, another
said he had no East Asian DNA but that he was ~8% Middle Eastern and ~1%
African. He's currently waiting for his 23andMe results, but mine said I was
only 0.5% Native American and that the remainder was European, so I'm guessing
it'll be similar for him.

~~~
notwhereyouare
If you did 23 and me, you should be able to add him as like a parent and it
will show you what you got from him in terms of your traits/dna

------
jecel
Either my understanding of genetics or most people's understanding is wrong.
Suppose you have a woman with roughly 100% African genes and a man with
roughly 100% German genes and they have a daughter. She will have 23
chromosome pairs, each with one African (A) and one German (G) chromosome.

Now imagine she has a bunch of children and let's ignore cross-overs to
simplify things. The 50% of genes that she contributes to each child can vary
from 0% A and 50% G all the way to 50% A and 0% G. So having a child with 16%
G would be perfectly normal (not even counting any contribution from the man,
which would make it even more complicated).

So the idea of dividing by 2 in each generation (great grandparent 100% X,
grandparent 50% X, parent 25% X and so me 12.5% X) is an extremely crude
approximation and having these genetic tests not match that doesn't
necessarily mean that they are wrong.

------
chaostheory
One thing that's good to know is that 23andMe and Ancestry don't currently do
genetic testing. They do genotype testing instead. Genotype testing is more
like a population comparison and it's not accurate, or only as accurate as the
genotype database you're being compared against.

~~~
klmr
I don’t know where you get this idea because genotyping _is_ (a form of)
genetic testing. And as for accuracy, human reference genome databases are
highly accurate. Sure, they’re not error-free — but then nothing is. _Ancestry
in particular_ is a tricky problem due to the highly variable representation
of different ancestries in the reference set.

By contrast, 23andme delivers high accuracy for genetic variants. Meaning, for
those variants in their reference set they can tell with very high accuracy
whether a given sample has a given allele. Interpretability of this
information unfortunately varies greatly because genetics is hard, and a lot
of the connections between genotypes and disease predisposition are complex
and still being fully discovered. It’s for this specific reason that the FDA
told 23andme off for providing disease predispositions; not because the
genetic test itself is inaccurate (it isn’t).

For simple (Mendelian) disease predispositions, 23andme is essentially as
accurate as any other for of genetic testing (which would at any rate _also_
use genotyping).

~~~
chaostheory
Ok - genotype testing is much less accurate as genome testing. A potential
consequence is the common experience described in the article. Genotype
testings's main advantage is cost.

On a side note, most of 23andme's reference set is limited to Europe, so it's
even less accurate for a lot of people. Maybe things have changed?

~~~
klmr
I’m still not happy with this characterisation. By “genome testing” I suspect
you mean whole-genome sequencing (WGS) [1]. First off, this is _also_ a form
of genotyping. And, depending on which definition of accuracy you’re using,
it’s no more accurate. It just provides _more signal_ (because it looks at
much larger parts of the genome than microarray genotyping [2] does). The
technology used by 23andme and DNA ancestry services (microarrays) will miss
some information, compared to WGS (= lower recall [3]). But importantly its
precision is no lower than WGS (in fact, until very recently it was _higher_
).

The fact that DNA ancestry estimates are inaccurate for some people is largely
unrelated to the technology (microarray vs sequencing), and rather to the fact
that our reference set _for ancestry_ is too sparse (especially outside of
Europe).

[1]
[https://en.wikipedia.org/wiki/Whole_genome_sequencing](https://en.wikipedia.org/wiki/Whole_genome_sequencing)
[2]
[https://en.wikipedia.org/wiki/DNA_microarray](https://en.wikipedia.org/wiki/DNA_microarray)
[3]
[https://en.wikipedia.org/wiki/Precision_and_recall](https://en.wikipedia.org/wiki/Precision_and_recall)

------
fisherjeff
> “They’re not telling you where your DNA comes from in the past,” he told me,
> “They’re telling you where on Earth your DNA is from today.”

But doesn’t AncestryDNA, in particular, have exactly the data one would need
to overcome that problem?

------
coldcode
I'd still like to see what mine contains. I know my ancestors back to the late
18th century with one exception - my fathers grandfather appears to have been
an imposter, as he does not exist in any record he should (Prussia), or at
least his background was not known to anyone I ever talked with who knew him
or knew someone who knew him. Genealogy is fascinating but hard to find data
that may have been destroyed in wars or country upheavals. At least at little
DNA information might provide an alternate connection but of course that might
itself be confusing. The past is often nebulous.

------
irrational
"Botched" seems too strong of a word for what the article is describing.

------
middleclick
I am not a scientist but in my limited research I have been led to believe
that these things are not entirely accurate.

~~~
LyndsySimon
Well, they're accurate but not precise.

What's useful is using the "DNA match" features of various websites to track
down genetic relatives and use their research to flesh out your family tree
beyond the point they intersect.

What's not useful is to use them to say "I'm 30% ____". It just doesn't work
that way. Even the Ancestry results that show I'm like 30%
"Ireland/Scotland/Wales" shows a whisker plot when you click in that gives a
margin of error of +/\- 35%.

~~~
drewmol
Hmm, my understanding leads me to expect: these companies to be more likely to
deliver repeatedly similar results (precise) upon multiple analysis of the
same tested specicime. It's the accuracy of the conclusions drawn from those
results that is more difficult to offer... Your thoughts?

