Using 23andMe African Ancestry Data to Reexamine the History of Slavery

Transatlantic Slave Trade Routes

This image shows the general direction of the triangular trade routes between continents during the transatlantic slave trade. Credit: Micheletti et al./ The American Journal of Human Genetics

The effects of the forced deportation of over 10 million African people during the transatlantic slave trade remain entrenched in the DNA of people from North, Central, and South America as well as the Caribbean. Now, in a paper appearing today (July 23, 2020) in the American Journal of Human Genetics, researchers have compiled genetic data from consenting 23andMe research participants to paint a more complete picture of African ancestry in the New World. By linking genetic data with historical records of the slave trade, the findings reinforce harsh truths about slavery in the Americas and uncover new insights into its marked history. These insights include the regions of Africa from which enslaved people were taken and the methods used to suppress and exploit Africans once they disembarked in the Americas.

“Our study combined the genetic data of more than 50,000 people on both sides of the Atlantic with historical records of enslaved people to create one of the most comprehensive investigations of the transatlantic slave trade,” says first author Steven Micheletti, a population geneticist at 23andMe. “One of the disturbing truths this research revealed was how the mistreatment of people with African ancestry shaped the current genetic landscape of African ancestry in the Americas.”

The researchers found that the genetic contributions from major African populations into the Americas match well with what they expected based on historical records, with most Americans of African descent having roots in Angola and Democratic Republic of the Congo. However, a closer look at precise African regions occasionally revealed a mismatch from what the researchers expected.

For instance, Nigerian ancestry is over-represented in African Americans in the U.S., likely due to the intra-continental slave trade, which the scientists say has only recently received attention for its impact on genetic variation. “By examining the Intra-American Slave Trade database, we concluded that much of the inferred Nigerian ancestry in the United States derives from transport of slaves within the Americas, primarily from the Caribbean,” says senior author Joanna Mountain, Senior Director of Research at 23andMe.

In contrast, researchers found that the genetic connections between African Americans and Senegambians were much lower than expected, given the number of Senegambians who disembarked in North America. “Because Senegambians were commonly rice cultivators in Africa, they were often transported to rice plantations in the US. These plantations were often rampant with malaria and had high mortality rates, which may have led to the reduced genetic representation of Senegambia in African Americans today,” Micheletti says.

Both slave-owner and government practices across the Americas had tremendous impacts on the distribution of African genetics as well. “Many slave-owners in the United States promoted enslaved people having children with one another for the purpose of maintaining a workforce, and even after slavery, they tended to segregate people of African descent,” says Micheletti. This is in contrast to practices in parts of Latin America, which supported “dilution” of the African populace after slavery was abolished. “In the early 1900s, sources state that the Brazilian government implemented immigration laws seeking to bring more Europeans into the country, presumably to have children with darker-skinned females and reduce African ancestry.” This practice of “dilution” is one reason the researchers believe that the proportion of people with greater than 5% African ancestry is five times lower in Latin America than in the US, despite Latin America receiving roughly 70% of all disembarked African slaves.

In Latin America, this dilution practice also partially explains why African women are found to have contributed substantially more to the gene pool than did African men. “Our analysis estimated about 15 African women had children for each African man in Central and South America, as well as the Latin Caribbean,” says Micheletti. This female gene bias is found in North America as well, concordant with reports of generations of sexual exploitation of African women occurring ubiquitously across the Americas. Mountain points out that, “The female bias is particularly shocking given that the majority of enslaved individuals were male.”

The researchers hope that, with this study, they can help those of African descent not only to find their roots, but also to understand how the experiences of their ancestors have shaped the genetic makeup of their communities. “This paper conveys how the racist and dehumanizing acts endemic to the slave trade led to different patterns of African ancestry across the Americas that we can see in the DNA of people living today. We hope readers grasp not only the impact of the slave trade but also the deep contributions enslaved Africans made to the history, economy, and culture of the Americas,” says Micheletti.

Reference: “Genetic Consequences of the Transatlantic Slave Trade in the Americas” by Steven J. Micheletti, Kasia Bryc, Samantha G. Ancona Esselmann, William A. Freyman, Meghan E. Moreno, G. David Poznik, Anjali J. Shastri, 123andMe Research Team, Sandra Beleza and Joanna L. Mountain, 23 July 2020, American Journal of Human Genetics.
DOI: 10.1016/j.ajhg.2020.06.012

Funding for this research was provided by 23andMe.

22 Comments on "Using 23andMe African Ancestry Data to Reexamine the History of Slavery"

  1. John Campbell | July 23, 2020 at 11:49 am | Reply

    It is unfortunate that these studies habitually fail to remind us that the enslavement of Africans was perpetrated originally (and for millenia) by Africans upon Africans. Mr white man merely took advantage of what an already long-established market. That it was the white man who eventually outlawed the practice is also forgotten.

    The past cannot be erased. It is what it is and it is, thankfully, in the past. It’s healthy to remember but it’s hardly just to seek blame of those who were late participants to what preceded them.

    It’s time to leave the racist blamegame in the past and move on together.

  2. John Campbell makes a good point. I try to remember that none of my people participated in this misery. However, I cannot blame the existing white population for the sins of the fathers and mothers either. What I would love to see happen is a coming together over the shared GOOD history we all share. And in America, we have much to make us grateful.

  3. It’s nice how the beneficiaries of the robbery of wealth and labor dismiss the consequences so easily. If my grandfather robbed your grandfather of his life savings and gave it to my father who passed it down to you would you feel the same. If after your grandfather was left destitute my grandfather and father passed laws that restricted you from trying to rebuild some wealth you lynched and barbecued is descendants would you look at it the same. Yes the Africans owe a debt but so do the Europeans who benefited.

    • John Campbell | July 23, 2020 at 7:19 pm | Reply

      Robbery of wealth? What wealth?! They were hunter-gatherer tribesmen who had nothing, not a bean. All they had was the rags on their backs, a mud hut for shelter and their indigeny of a land that barely allowed them to survive.

      That’s not to dismiss their humanity or their denial of those rights but then, if they were so very precious to you, you’d fight to the death to preserve them. That they ended up enslaved was as much a failure on their own part to defend those rights as it was the enslavers who originally enslaved them and sold them to the white traders. What they gained was security, regular food, reliable shelter, clothing worthy of a civilised human being. Certainly they lacked rights and freedoms, but rights and freedoms are things you fight for and defend. And facing the very real likelihood of starvation, inter-tribal warfare or disease, who wouldn’t trade freedom for the sake of clean water, food and shelter?

      And then let’s consider the fact that the white man then thought twice of his advantages and changed the laws of our societies to free them and grant them rights within lands we had gone to great effort and expense to civilise? They weren’t shipped back to Africa or culled like cattle, they were given the opportunity to make their own way as free folk. You only have to glance at the many celebrated black people our world has today to appreciate the effect that act has had on those Africans who were once a destitute and desperate.

      Was it ugly? Yes. Was it unjust? Yes. Was it unfair? Only those who suffered the desperation of tribal Africa can answer that question. The spoiled brats of today wouldn’t last a day in that reality. Seems to me someone’s biting the hand that fed them.

    • Hear! Hear!
      In any story like this, it never takes long before they show up to try White-splaining away their part in this horror.
      “We were just buying what was being sold”
      “Well whataboutthem, they did it too”

      It’s the same excuse criminals give for their behavior, so I guess we should be happy that at least they are openly admitting to their crimes while trying to shift/share the blame. Kudos.

      • John Campbell | July 24, 2020 at 1:47 pm | Reply

        White-splaining, is that like “telling the unpalatable truth that you wish to ignore”? I have made no excuses for our ancestors behaviour, my point is to remind all in this discussion that while yes, they did do wrongs and profited from them, there was also a lot of good done and many benefits ultimately enjoyed. Spo to behave towards modern white society as if we’re somehow responsible for our ancestors failures would be like me blaming the Africans for allowing themselves to be taken as slaves. Which is, ultimately what they did.

        But I don’t blame them, because I’m not ignorant to the fact that responsibility is never one-sided.

        Is someone truly a criminal if valuables are left in the open for picking up? And if that “criminal” then permits the facility to recoup your loss (through your own carelessness), have they done any wrong?

        I think you are being terribly narrow-minded.

  4. Yohannes Gezu | July 23, 2020 at 10:13 pm | Reply

    Mr Campbell, I west no time to respond to your ignorance but let me ask you simple questions.
    1) What wealth you ask. Do you believe the white man was in Africa for more than 500 years to bring us wealth or for looting Gold and dimond etc?
    He was all over Africa eating what if we had no beans? Did he brought us food or guns, or gonoria and syphilis? Don’t you know most Europeans wealth came from Africa? Ask king Leopold when you see him.
    2) If the land was barely allowed us to survive, do you believe the white man brought us land from Europe or a or a phoney Bible? Don’t you know Only 1% of the white population controlled Zimbabwe and South Africans furtile land for 300 years?
    3) You also said Hunters and gatherers who had nothing, only rags on their backs? Please read Mansa Musa king of Mali who has Gold more than the universe all together.
    4) Their indigeny of land that barely allowed them to servive? Well we had a land looted for 500 years by the white man and he is out and the Chinese are coming for our indigeny land again read history please.
    2) A mud hut for shalter? When we built the pyramids and the Axum obelisk may be you had sky scrapers too? What a shame.

    Please be respectful to your fellow human beings. I know 100% you too came from Africa 100,000s years ago but acting you are from Mars.


    • I totally agree with Mr. Campbell.
      “White slavers” bought already enslaved people. They didn’t make them slaves. Maybe you should be dealing with your African ancestors who made your neighbors slaves.

    • John Campbell | July 24, 2020 at 2:19 pm | Reply

      1) In the following 150 years since slavery was outlawed, did those Africans take advantage of those resources? NO, they relied on the knowledge, expertise and industry of the white man to find those resources, organise the infrastructure and ultimately improve black lives and welfare in the process. Had they not, the blacks of Africa would still be killing one another for goats… as many still do to this day. This is not a racist point of view, it is an observable fact of history.

      You think Africans were the first people to suffer diseases? White people have suffered far more from them! And what difference a death by gonorrhea than by your axe-wielding neighbour, or the Tsetse fly, or malaria?! You’d think death was a white man’s invention! And you forget that Mr white man’s ingenuity has improved African housing, roads, transport, infrastructure and governance. Our medicine has saved countless lives. The richest African country of them all was founded by white settlers and is now run by black people to the benefit of all citizens. Are you going to blame all white people for the greed of the few who lived by feudal principals?! If you are, then you’ve lost the argument before you have started.

      2) If the land had provided more, the people would have had the resources to achieve more. The fact they hadn’t (and in many cases STILL haven’t) tells you the land isn’t as generous as one might hope. In fact, much of it is a disease-ridden no-man’s land where only the most resourceful of all mankind can eke out the poorest of lives. The white man’s fortune was built upon the richness of the lands from which he hailed and his capacity to develop its resources for the benefit of all… not just the dictators.

      3) Having gold doesn’t make you special. It means you own a lot of metal. What you DO with it makes the difference! Did he make his people wealthy? Did he feed and clothe and build the roads and houses his people needed? If so, how did his kin end up enslaved?! Seems to me he failed miserably DESPITE the gold!

      4) The white man could only loot the land if he had the ability to do so. Again, they had the resources yet achieved nothing with them… to the point of failing in their own security! As the old biblical saying goes… Hell mend them! Yes, history repeats because they don’t learn the lesson.

      5) And what labour was used to build those pyramids? Oh, you forgot… it was SLAVE LABOUR!! And why were they built… to house skeletons, not humans! We at least built better houses, better roads, better clothes, better furnishings, better governments, better transport, better cities, better water supplies, better medicine, better engineering, better technologies… shall I go on?

      Take a good hard look in the mirror and remember that the very technology you are typing on and the nice warm building you are sitting in was developed as a result of white societies efforts. And yet we share those wonderful benefits with everyone precisely because we ARE NOT RACIST.

      No society is without blame for one folly or another, whether it’s taking advantage of another or simply failing in your duty of self-preservation. And to point out the FACTS of history is never disrespectful. In fact, it is deeply disrespectful to everyone to conveniently ignore those facts in order to grind a rubber axe.


  5. Brilliant comment! Bravo.

  6. If you participate in slavery you’re guilty period. Seems like you’re justifying it.

    • Is fanny see an white man talk about “leave the racist blamegame”. Please…

    • John Campbell | July 24, 2020 at 2:26 pm | Reply

      The Bible justifies slavery. So I suggest you blame every Christian. As for the white man, he outlawed slavery.

      So, who are you going to blame? The white man who made a mistake then freed the slave, or those Christians (white, black or otherwise) who continue to hold to the idea and even pledge their hearts to it?

  7. @John – I believe you need some better historic literature, as you’re dead wrong about what Africa was like back then. It’s a myth being purported to make people feel better about what happened in Africa. When the white man arrived, many civilisations were destroyed, civilisations that were way ahead of the Europeans in many ways. But with guns, bibles and disease, the white man destroyed so much and for what? To quench some underlaying desire to rule the world?

    I didn’t learn about these things in school. In fact, the first time I even knew the country I was born in had any involvement at all in the slave trade, was from a comic book. I now know much better and I’m disgusted by the fact this isn’t being taught in schools.

    Please, for your own sake of nothing else, open up your mind and do some research before you post silly comments about something you so clearly know so little about on the internet.

    • John Campbell | July 24, 2020 at 2:29 pm | Reply

      Those civilisations (as few as they were, were destroyed by their own failures. Not the white man. None of the civilised peoples become slaves, they were the enslavers who sold the slaves to the white man. Get your facts right.

  8. Mr. Campbell the wealth that was taken was the same wealth that brought Europe out of the Dark Ages

    1. For 700 years Moors(Africans) conquered and bred with the population in the Iberian Peninsula. Probably how Columbus heard about the New World
    2. For 5000 years the Ancient African Egyptian civilization ran the world. 400 years doesn’t make you inherently superior.
    3. If your not careful your Nordic women with their habit of breeding with Nubians will end your existence.
    4. The slavery practised in the United States by the Pagan/ Christ and was the most barbaric in history.

    • John Campbell | July 24, 2020 at 2:40 pm | Reply

      Oh for goodness sake pick up a calendar!! The Europeans were many centuries out of squalor by the time Africa was even set foot upon by white settlers. As for the wealth of its natural resources, they only became available to Europeans in the eighteenth century, and for the most part it was ivory, not the diamonds and other precious minerals- they came much later!

      1. Well there’s an utterly useless factoid in this discussion.
      2. The Egyptians ran Egypt. Period. The world didn’t even know who they were or that they existed.
      3. Clearly you are a troll.
      4. Now I am crying with laughter.

      • Nice how facts are easily dismissed by you with snide comments. Must be that Neanderthal blood boiling. 😆

  9. Ask any Evolutionary Anthropologist what he or she thinks of DNA results from 23andMe, Ancestry and the other consumer testing companies, and you will hear a hardy belly laugh! Their results are Garbage. NONE of them have a deep enough sample base archive to be meaningful and Educational / Research DO NOT share their libraries with this 2-bit DNA pretenders. There have been numerous reports of people doing multiple tests with 23andMe and others and getting completely different conflicting results. EXAMPLE 22andMe only had a dozen DNA comparative samples for ALL OF South East Asia! Everyone is told they have a “Sub Saharian” ancestry (no s#!t, we ALL came out of Africa!). Dont be fooled by these consumer DNA labs, they are worthless, just a money maker for opportunistic. PhD Evolutionary Anthropologist Univ of Chicago.
    And PS: Every Ethnic Society HAD Slavery for Centuries, Thousands of years! Hawaiians did for example for hundreds of years before Cook landed there nearly 300 years ago!

  10. Lance patrick bettencourt | August 21, 2020 at 1:16 pm | Reply

    Mr. John Campbell
    You have printed the truth more than most people would. This all happened due to a stronger group of people praying on a weaker group of people. It is done today and it will be done tomorrow it is the nature of the beast eat or be eaten fight or be beaten the problem I see is we spend too much time trying to figure out why things happened when we should be spending that time on fixing things and changing things because we know nothing is ever fixed. One more thing to think about All races and all classes have been enslaved by other races and other classes this is why the strong survives and who has the gold makes the rules just look at it this way are you sitting at the table eating or are you on the table being eaton

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