"My
grandfather was caramel-skinned with black eyes and thick, dark hair,
and until he discovered that he was adopted, he had no reason to suspect
that he was not the son of two poor Mexicans as he’d always been told.
When he found his adoption papers, according to family lore, he pestered
the nuns at the Dallas orphanage where he had lived as an infant for
the name of his birth mother. Name in hand, at 10 years old, he hopped a
bus to Pennsylvania, met his birth mother, and found out that he was
actually Syrian.
At least that’s what we thought until my Aunt Cat mailed a tube of her spit in to AncestryDNA.
Genetic
testing suggested that my aunt’s genetic makeup was only a tiny bit
Middle Eastern—16 percent, not the 50 percent you might expect if your
father was a full-blooded Syrian, as my grandfather believed himself to
be. The rest of her Ancestry breakdown provided some explanation, but
mostly more confusion. While we typically think of the Caucasus as
countries on the Black and Caspian seas like Turkey and Armenia,
Ancestry’s test also said it includes Syria. According to Ancestry, the
Caucasus accounted for another 15 percent of my Aunt Cat’s DNA. What
about the other 20 percent? One line-item stood out as something my aunt
hadn’t expected, based on what she knew about either of her parents:
She was 30 percent Italian-Greek. My mother’s test revealed similar
results.
This caused a minor family scandal.My
grandfather’s mother was born in Pennsylvania, but she had lived in an
insular Syrian community that never really assimilated. She became
pregnant as a teen by her father’s best friend. The assumption had
always been that he was Syrian, too. If we weren’t who we thought we
were, well, then, who were we?
“I guess we never knew the name
of Dad’s father,” my aunt told me, bemused. Suddenly it seemed as
though all along we had been missing a gigantic puzzle piece of
information about our family tree. At least, my aunt quipped, this was a
solid explanation for why she loved pasta.
It’s right there in the fine print of any consumer DNA test, if you bother to read it: DNA testing can come with identity-disrupting surprises,
be it an unexpected relative, genetic condition, or, in our case,
heritage. But something about this particular surprise didn’t feel quite
right."
My Aunt Catis
our family’s amateur genealogist, and she has logged hundreds of hours
both on Ancestry.com and in my grandmother’s attic, piecing together the
story of our family tree. She’s found countless third, fourth, and
fifth cousins with ties to Syria, but no one from either Italy or
Greece. In her twenties, she even visited my grandfather’s biological
mother and aunt. She recalled them passing around a hookah, yelling in
Arabic, and expressing repulsion at the American-style cold cut platter
served at a community function. Given how segregated the family was, it
seemed like a stretch, she told me, to imagine that anyone had ever had
so much as a friendly conversation with an Italian. I suspected
the error might lay not in my family narrative, but in the DNA test
itself. So I decided to conduct an experiment. I mailed my own spit
samples to AncestryDNA, as well as to 23andMe and National Geographic.
For each test I got back, the story of my genetic heritage was
different—in some cases, wildly so.
My
AncestryDNA test revealed that I, too, had geographic roots in the
Middle East, the Caucasus, and Southern Europe, along with the expected
big dose of Scandinavian from my very Norwegian father. Weirdly, though,
my percentages of Middle Eastern and Caucasus were almost as high as my
mom and aunt’s, though you would expect them to be closer to half.
It
got more confusing from there. My test through National Geographic
(which partners with the DNA sequencing company Helix for its test) gave
me even more links to the Middle East, with 16 percent of my DNA from
Asia Minor, 6 percent from the Persian Gulf and 9 percent something
called “Jewish Diaspora.” Unlike AncestryDNA, National Geographic’s test
assigns your heritage to broad regions instead of modern nation-states.
But I could infer that, according to National Geographic, I was less
Scandinavian based on my percentage of Northwestern European. I was also
more Southern European and, for fun, now had a good chunk of Eastern
European thrown in there, too.
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. And no
Eastern European at all.
I also uploaded my 23andMe data to GenCove,
a small ancestry-test startup founded by scientists. Based on the exact
same data that 23andMe had crunched, GenCove reported that 8 percent of
my DNA was from the Indian subcontinent. 23andMe had found I had no
South Asian DNA at all.
Fourtests,
four very different answers about where my DNA comes from—including
some results that contradicted family history I felt confident was fact.
What gives?
There are a few different factors at play here.
Genetics
is inherently a comparative science: Data about your genes is
determined by comparing them to the genes of other people.
As
Adam Rutherford, a British geneticist and author of the excellent book
“A Brief History of Everyone Who Ever Lived,” explained to me, we’ve got
a fundamental misunderstanding of what an ancestry DNA test even does.
“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.” Ancestry,
for example, had determined that my Aunt Cat was 30 percent Italian by
comparing her genes to other people in its database of more than six million people, and finding presumably that her genes had a lot of things in common with the present-day people of Italy. Heritage
DNA tests are more accurate for some groups of people than others,
depending how many people with similar DNA to yours have already taken
their test. Ancestry and 23andMe have actually bothpublished papers about how their statistical modeling works.
As
Ancestry puts it: “When considering AncestryDNA estimates of genetic
ethnicity it is important to remember that our estimates are, in fact,
estimates. The estimates are variable and depend on the method applied,
the reference panel used, and the other customer samples included during
estimation.”
That the data sets are primarily made up of
paying customers also skews demographics. If there’s only a small number
of Middle Eastern DNA samples that your DNA has been matched against,
it’s less likely you’ll get a strong Middle Eastern match. “Different
companies have different reference data sets and different algorithms,
hence the variance in results,” a spokesman from 23andMe told me.
“Middle Eastern reference populations are not as well represented as
European, an industry-wide challenge.”
As
a person of Syrian descent, the British genealogist Debbie Kennett told
me, my test was simply not going to be as accurate as fellow Americans
whose relatives skew more European. “The tests are mainly geared for an
American audience, and they tend to not have a lot of Middle Eastern
ancestry,” she said.
Likewise, Kennett said, because
relatively few English people have taken tests from American companies
like Ancestry or 23andMe, residents of the U.K. are likely to find less
useful results.
“A lot of
English people come up with a low percentage of British. My dad was only
8 percent British and most of his ancestors as far back as I can trace
came back from Great Britain,” she told me. “People in America come up
with much higher percentage of British, often.”
Another
anecdote that stuck with me came from my friend Alexis Madrigal.
Initially, he said, his Mexican family came up as Arab North African,
which was surprising. As 23andMe refined its test and its data set grew,
it also refined the results: Now, he was descended from Jewish people
from Southern Europe. The number of Madrigals in central Spain had long
led the family to suspect that their migratory path to Mexico had at
some point passed through this region. As more people took the test, the
picture of where his family was “from” changed. The Canadian
bioethicist Timothy Caulfield shared a similar story. At first a DNA
test revealed he was entirely Irish, but as the data set changed, he
gradually became less Irish.
When we talk about “ancestry,” we
also don’t always mean the same thing. Ancestry just implies people
you’re descended from. But when? In America, we often mean whenever our
relatives came to the U.S. On my dad’s side, I expected to see a lot of
Scandinavian, because just a few generations ago my great grandparents
came from Norway to North Dakota. On my mom’s side, my grandmother has a
relative that came to America on the Mayflower. Both are what come to
mind when I think of my “ancestors,” but they are separated by several
generations and hundreds of years in time. Rutherford pointed out that
if we went 5oo years back, my ancestors were probably from all over
Europe.
“You and I are probably fifth cousins,” he said. Where
your ancestors are from depends on what period in time you’re talking
about. Why don’t I instead say I’m 50 percent North Dakotan and 50
percent Texan?
Tests
also differ from one another because they’re simply looking at
different things. The results of ancestry tests aren’t based on a
reading of your whole genome. The vast majority of every human’s DNA is
identical to any other human’s. Ancestry tests look at SNPs, the places
on your genome where an individual letter tends to differ between
people and give us insight into characteristics like disease, ancestry,
and physical appearance. When an SNP occurs within a gene, then, in
science-speak, that gene has more than one allele, or alternate forms of
a gene that exist in the exact same place on a chromosome. To make
matters more confusing, some tests look at mitochondrial and Y
chromosome DNA, while others don’t.
The CEO of GenCove, the
company where I had uploaded my 23andMe data to get drastically
different results, told me that even though he expects a fair amount of
variability between algorithms, even he was surprised at how differently
his company and 23andMe had interpreted my DNA data. He asked me to
also upload my Ancestry data, and ran both data sets again after
GenCove’s algorithm had been updated. The results were all over the map.
“To be honest I’m a little confused about what’s going on,” CEO Joseph Pickrell told me. Each
testing company is looking at different alleles from different parts of
the genome, and using different algorithms to crunch that data. (You
can see a list of how company tests differ here.) It’s worth mentioning that genetics is also probabilistic: just because you have the gene, doesn’t mean you have the trait.
“One
British company identified an allele in me that gave me ginger hair,
and 23andMe didn’t,” said Rutherford. “That’s a simple case where they
just used different alleles. That’s relatively simple to explain.”
And
sometimes, the algorithms might just get it wrong. Rutherford told me
his 23andMe test came back with a tiny amount of Native American DNA.
The finding actually linked up with one anecdote from his family lore,
about a relative of his father’s that was a Native American tribesman
and horse jumper in a British traveling circus.
“As
a geneticist, I am absolutely convinced that they’re not related,” he
told me. “It’s just statistical noise that happens to coincide with this
cool story.” Statistically, it’s unlikely that such tiny amount of
Native American DNA would have been enough to show up on Rutherford’s
test. A
big problem is that many of us have a basic misunderstanding of what
exactly we’re reading when Ancestry or 23andMe or National Geographic
sends us colorful infographics about how British or Irish or
Scandinavian we are. It’s not that the science is bad. It’s that it’s
inherently imperfect, an estimation based on how much our DNA matches up
with people in other places around the world, in a world where people
have been mixing and matching and getting it on since the beginning of
human history.
“You’re
creating different algorithms and you’re using different data sets as
your reference points, so it makes sense that you’re going to get some
different responses,” the Harvard geneticist Robert Green explained to
me, as I tried to make sense of my own DNA data. “It’s not that one’s
wrong and one’s right. It’s that there isn’t an agreed-upon approach to
pick the right number of markers and combine them mathematically.
Everyone is sort of just making it up as they go along.”
At
the continental level, said Kennett, ancestry testing is useful. It can
tell you pretty reliably whether you are African or Asian or European.
It can also reliably identify close familial relatives, as distant as
third or fourth cousins. Otherwise, Kennett said, “take it with a large
pinch of salt.”
Nearly everyone I interviewed for this story said
that, taken with the right mindset, ancestry DNA testing can be fun. As
more people take DNA tests and company data sets grow, the results from
those tests will also become more detailed and accurate. Anecdotally, I
saw this in my own results. Ancestry has the biggest DNA database, and
its interpretation of my DNA was also most in-line with what I expected.
“The
more people that take tests, the better the experience for all of us,”
an Ancestry spokesman told me. “Your DNA does not change, our science
does.” But consumer genetic testing companies have also fueled the
misunderstanding of their products, suggesting that those colorful
results reveal something profound about what makes you, you.
Take
this AncestryDNA ad about Kyle Merker, who, the ads explains, grew up
German, wearing a lederhosen and performing traditional German dances.
Then an AncestryDNA test revealed he was actually Scottish and Irish. He
bought a kilt.
Ancestry.com
is suggesting—quite heavy-handedly—that your DNA can define your
identity. A few changes to those As, Gs, Ts, and Cs, and all of the
sudden you’re river dancing. “Your
culture is not your genes,” said Caulfield. “But the message these
companies send is somehow where your genes are from matters. That’s not
necessarily constructive. The role of genes in who we are is very
complex. If anything, as genetic research moves forward we’re learning
that it’s even more complex than we thought.”
In truth, your
specific ancestors actually have relatively little impact on your DNA.
Some 99.99 percent of your DNA is identical to every other human’s.
We’re mostly just all the same. But instead of embracing our genetic
similarities, we cling to those differences as symbols of what makes us
unique. Consumer DNA testing tends to reinforce that—even though the
difference that one test reveals might not even exist in another.
“These
companies are asking people to pay for something that is at best
trivial and at worst astrology,” said Rutherford. “The biggest lesson we
can teach people is that DNA is probabilistic and not deterministic.” Your
DNA is only part of what determines who you are, even if the analysis
of it is correct. Plenty of people love pasta, with or without Italian
DNA.
If the messaging of consumer DNA companies more
accurately reflected the science, though, it might be a lot less
compelling: Spit in a tube and find out where on the planet it’s
statistically probable that you share ancestry with today.
Learning
he was Syrian did not seem to impact my grandfather’s identity as a
Mexican man. And how could it? His life story was the story of so many
children of immigrants. His father, Manuel, had swum the Rio Grande from
Mexico to America in hopes of a better future. He worked as a waiter,
and my great-grandmother as a seamstress. At age 10, my grandfather was
sent to work at a Coca-Cola bottling plant to help the family make ends
meet. He lost a finger. Eventually, he met my blonde-haired, blue-eyed
grandmother and moved to California, hoping to raise their children
somewhere it would matter less that one of their parents spoke Spanish
as a first language.
But
me, I don’t even look the part. I’m fair with blue eyes. As a kid, I
remember wincing when my friend’s mom made xenophobic comments directed
at Mexicans, never suspecting her daughter’s fair friend had some
Mexican ties, even if they were not by blood but by heart. As an adult, I
learned Arabic and perfected my tamale-making, all in search of some
sort of an identity fit. When my grandfather was dying, I struggled with
the relationship between DNA and cultural identity. I wondered what
would become of my Mexican heritage, once my last living link to it was
gone.
In the end, I finally found the same wisdom my
grandfather never seemed to question. Sometimes your heritage doesn’t
have anything at all to do with your genetics—and I didn’t even have to
spit in a test tube to figure it out."
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