Who Planted The Family Tree?

by Emily Chang, Joanna Mountain and Mike Macpherson


Click on the image above for a larger version of this chart, which shows that some ancestry combinations are more common than others in the 23andMe database.

Given the “melting pot” nature of the United States, it is not surprising that most Americans have mixed ancestry.  Like many of my fellow citizens, my ancestry is a long recipe: a bit of English, a dash of German, a pinch of Hungarian.  My children, should my husband and I have kids, will have Chinese ancestry, too. Such mixed ancestry is becoming more and more the norm — and genetics turns out to be a very useful tool to explore it.

Traditionally, genetic ancestry focused on two particular pieces of DNA, mitochondrial DNA and the Y-chromosome. Your maternal line includes your mother, your maternal grandmother, her mother before her, and so on; likewise, your paternal line includes your father, your paternal father, his father before him, and so on. The paternal line is determined using the Y chromosome, which determines whether a person is male and which only men can pass down. The maternal line is determined using the DNA found inside mitochondria, small energy-producing cellular machines that come with their own set of genetic blueprints. Both men and women have mitochondrial DNA but only women pass on their mitochondrial DNA to children.

These days, genetic ancestry tools like 23andMe use DNA from all of your 23 pairs of chromosomes to offer insights into your heritage. But information about maternal and paternal lines, which can reflect ancestral origins, can still yield interesting insights.

This figure shows the paternal line in blue and maternal line in pink. Your maternal grandmother and paternal grandfather are members of your maternal and paternal lines, respectively.

Our large customer database shows that some ancestry combinations are more common than others among our customers.  Given a pair of ancestral origins, there are two ways to combine the maternal and paternal lines: a maternal-line of the first ancestry with a paternal-line of the second ancestry or a paternal-line of the first ancestry with a maternal-line of the second ancestry.

Our database shows that these two different ways of combining the maternal and paternal lines are not equally common, indicating gender trends in mating. For instance, about 3.5 times as many 23andMe customers have a maternal line indicative of African ancestry and a paternal line indicative of European ancestry than the reverse. This mating trend probably reflects, in part, a disgraceful period in the United States’ past in which white male slave owners fathered children with enslaved African American women rather than recent trends in interracial marriages. More recent marriage patterns actually reflect a trend in the opposite direction. The 2010 US census shows that a “white” wife and “black” husband is 2.3 times more common than a “white” husband and “black” wife [note: the terms “black” and “white” were the descriptors used in the US census report].

The maternal and paternal lines of the 23andMe customers, thus, tell the sad truth of the treatment of enslaved African American women. In one episode of the television program Finding Your Roots, Condoleezza Rice says this aspect of United States history is an “unhealed wound in America” and that we have trouble talking about what really happened during slavery. She is right. Most of us would rather not talk about the rape of enslaved African American women, but DNA isn’t shy about addressing this ugly truth. As we study and learn about these genetic patterns, we begin to face one of the most disturbing aspects of United States history — a vital step towards healing that unhealed wound to which Rice referred.

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A similar but less extreme pattern was observed for individuals of Asian and European ancestry; about 1.7 times as many 23andMe customers have a European paternal line in conjunction with an Asian maternal line than have an Asian paternal line with a European maternal line. The reason for this particular mating trend can not be traced to slavery and may have more complex sociological and historical origins.  Regardless of its source, however, the trend is supported by other studies. The large PEW study on interracial marriage released this past February, which observed that Asian American women were more likely to have an interracial marriage than Asian American men, and the US census bureau, which captures a wider segment of our society than the 23andMe database, shows an even stronger trend — a “white” husband and “Asian” wife is 2.4 times more common than a “white” wife and “Asian” husband [note: the terms “Asian” and “white” were the descriptors used in the US census report].

Our DNA holds a lot of information. It tells us not only who we are but also who we, collectively, were. The mating trends seen in the maternal and paternal lines of 23andMe customers reflect complex sociological and historical truths, even some historical truths that are difficult to face. Genetics helps us learn more about who we are and who we were, hoping that such knowledge will translate into less racism and more appreciation for people who are different from ourselves.






  • K. Stone

    I find it horrifying that the poster “George Jones” attempts to justify the “economics of rape”. What’s next–justifying the “politics of rape” during war? Or allowing rape as a means of institutional control within prisons?

    Btw, I’m fairly certain that the “relations” enslaved African women had with white slaveowners, overseers, and most any other random white man who could rape them with impunity were, by definition, not “voluntary” or the product of “true love”.
    Nowhere did the author state that all white men raped black female slaves–just as not all soldiers in war rape the women of their antagonists and not all men in prison rape their fellow inmates. The fact that anyone has been raped at all is a shame and a stain on humanity; and can in no way be justified for any reason. I’m guessing that “George Jones” is a middle-class, white male who is highly-unlikely to be subjected to rape at any point; and perhaps lacks the empathy to realize just how hurtful arguments like his are to many. This is why we have and will continue to have the “unhealed wound” Rice talked about. It is fairly obvious that evil triumphs, lingers and reverberates when so-called “good people” stand silent and do nothing; or spend their time making convoluted excuses with the hollow essence of “Well, it wasn’t me; it was them”.

    And I don’t recall white indentured servants needing an Emancipation Proclamation to free them–sorta.

  • Alice Nordquist

    The economics of slavery in America is a well studied topic.

    http://www.nber.org/chapters/c0606.pdf

    In slave economics, the female slave is viewed as CAPITAL ASSET for the slave owner and her children are the DIVIDENDS. This CAPITAL can both apppreciate and depreciate, just as other assets would.

    This much the same way in tree economics, where the MAPLE TREE FOREST is viewed as a CAPITAL ASSET for the owners and the MAPLE SYRUP are the DIVIDENDS.

  • Rena Griffe

    Until I read the comment by George Jones, it didn’t seem to me that this article was painting “white Americans and their ancestors as sinners.” I re-read the article, yet still didn’t see any literal or proverbial pointing of the finger. Concerning the treatment of African slaves by their masters, miscegenation is part of our nation’s history in myriad ways, and the past continues expressing itself through our genes.

    It always intrigues me when people feel the need to defend themselves against history (or downplay it) as though it’s an attack against them personally. Even if Mr. Jones (or anyone) had ancestors who owned or even–gasp–had “relations” with slaves, that would not make him (or anyone) in the least bit culpable or responsible to owe an explanation, a justification, or an apology. But so often people dismiss the experiences of others with their own bias as an emotional reaction seemingly akin to guilt emerges, a defensive stance that creates division since it was the defensive mechanism that, in fact, fired the initial shot.

    Very interesting article, overall.

  • Rena Griffe

    (By the way, I mean no attack of George Jones and apologize to him personally if I have misunderstood his viewpoint.)

    As a multigeneration mixture of races, I have long had a very personal connection to the history currently being explored genetically by many people curious about how their genes answer the question”who am I?” Long ago it seemed clear to me that I had no ground on which to cast blame on anyone with regards to the past. It may seem an oversimplification to some, but the past with its mixture of good and bad ultimately flowed into the creation of my life on this Earth. It’s up to me to determine how best to live that life. (Or, in other words, I cannot point the finger without wounding myself, because when it comes to slavery, I represent both sides.)

    Having said that, this history for myself, and for many others is personal, not theoretical, and much more emotional than intellectual. It doesn’t mean that there’s no mental engagement with the issues, but it’s the heart, and not the head that leads. It was my heart, and not my head, that lead me to read “Who Planted The Family Tree?” in the first place because it reminded me of my own deep relationship with my ancestry.

  • http://thisisnotpinoy.tumblr.com Nes

    Well said, Rena. The amount of micro-aggressions committed by George through this article is apalling. The article is scientific at heart, but in no way does it even suggest that the emotional turmoils of stories found in our DNA are to be qualified by science. The fact is that Georgey here does holds much emotion over this genetic history–especially obvious when he uses his male privilege to downplay Miss Stone’s appropriate reaction as a women into the ravings of a “drama queen”, despite attempts to hide his racial bias and insecurity behind the science of economics.

    The study of genetics is the perpetual discovery of the meaning of what it is to be human. And as with all things regarding humanity–yes, even inscience–it can only be fully understood with a measure of compassion, free-thinking, and above all wisdom, as the knowlege we obtain is worthless without the wisdom to apply it for the betterment of the soul.

  • George

    There is the assumption of rape in every case.That also assumes the type of man who would rather fight an unwilling slave or have sex with an unresponsive female. The master of a plantation would have been, in terms of wealth and power, the most desirable male on the property. Some women like to date the boss. It would take less energy to find a willing slave than to fight an unwilling one.
    Yankees and others from the Northeast spin history but social interaction on plantations would have been complex. The owner and his family would grow up with slaves born on the property and know them from childhood. Their stations would be different but there would be familiarity. A many times great uncle of mine had 2 or 3 children with a half Indian slave. A white descendant met a black descendant in a waiting room. They had the same last name and talking discovered a common great x grandfather. The black one said their family tradition was that he’d been good to his slaves so they claimed him as a grandfather. Some people never miss an occasion for some white male bashing.

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