Make That Three Degrees of Separation

Check out this post to see an illustration of the three degrees of separation between guests on Finding Your Roots.When we learn about our ancestors, who they were and where they came from, the discoveries become part of how we define ourselves and how we understand ourselves to be unique. The PBS series Finding Your Roots has taken this a step further, showing us how much we share with others and how interconnected our stories are.

23andMe Scientist Mike Macpherson going over connections between guests with Prof. Henry Louis Gates, Jr. and a Finding Your Roots producer.

This has been a theme of the 10-part series, something that the show’s host, Professor Henry Louis Gates, Jr., has returned to again and again – that despite our differences, whether racial or cultural, Americans are more interconnected than we know.It isn’t just that our stories share parallels, but that the connections run deep and can be seen in our DNA. It’s an irony that as the world’s population has grown exponentially in the last 500 years – from about half a billion to now seven billion – we are actually closer and more connected.During the filming of the show, Professor Gates visited 23andMe and talked to scientists Mike Macpherson and Joanna Mountain, both of whom served as consultants to the show. At one point Macpherson taped up photographs of the roughly two-dozen guests who appeared in Finding Your Roots. Then he sketched out the genetic connections that linked this seemingly random collection of people.This was the first time that someone had demonstrated the genetic connectivity of any two people on earth. Macpherson was able to make some surprising links that connected, for example, Martha Stewart to Samuel L. Jackson, and Barbara Walters to the Imam Yasir Qadhi.Unlike previous examples that relied on social connections – friends of friends of friends – this connection is through cousins matched within 23andMe’s database of over 150,000 people.This wasn’t just a parlor game. Indeed that notion that any two people – a cop in New York and a street vendor in Mumbai, say – could be connected through five other people was first written about by Stanley Milgram from experiments he did in the late 1960s. It’s a little more complicated than what Milgram theorized but he got the gist right.

23andMe scientist Mike Macpherson sketching connections between the guests on Finding Your Roots as Prof. Gates looks on.

These previous theories of connectivity focused on social connections; the idea that we are all – all seven billion of us – linked to each other by six degrees of separation. This theory of connectivity even spawned a game named after one of Gates’ guests,  “Six Degrees of Kevin Bacon.” The game links any actor to Kevin Bacon by five other performers. Bacon – whose wife Kyra Sedgewick was also on the show – said for a long time he hated that his name was the punchline for a joke. But he has since embraced it and is using the idea of social connections to link people to worthy causes.More recently Facebook and LinkedIn have shown that just four “connections” could link any two people together.Macpherson connected the Finding Your Roots guests via a much shorter genetic chain. Any two people are connected through just one or two other individuals.Why is this a revelation?It’s new because this isn’t the notion that you are connected to someone else because of who you know. It’s the notion that you are connected to someone because of who you are related to.This is a manifestation of human history and human migration over the last 500 years. People are no longer isolated by geography and so the differences between people are smaller than in the past .Perhaps in no other place has the convergence of people of different cultures and histories been as dramatic as the Americas. And while the clash of cultures and histories has been both painful and brutal at times, it is what forged our history more than anything else, Gates argues.“I’ve always thought that it was that story of America,” said political commentator Linda Chavez in the last episode in the series.People came here from all over the world, some voluntary and some involuntary, and mixed, she said, “and that’s made us stronger.”This post by 23andMe Content Editor Scott Hadly and 23andMe Senior Director of Research Joanna Mountain first appeared last week on PBS’s Finding Your Roots website. It was one of a series of posts by 23andMe. Dr. Mountain was a consultant for the the 10-part series.
  • Maureen Markov

    Sounds interesting, is it necessary to watch the entire show to see a 3 degree samples or example, can one also be mentioned here in more some detail to illustrate the idea?

  • Mike Wilson

    There in lies the problem using DNA for Geneology. We are all so inter-related, I have 3rd to distant cousins from the Urals in central Russia all the way westward to the west coast of the US and probably a few others at 23andme in addition to some of the above. Then there are others in South America, South Africa, India, Philipines and NZ and that’s making all this a little more complicated as the word spreads and more start doing this.

  • It’s Milgram, not Milgrim.

    • ScottH

      Thanks Gustavo. We’ll make the correction.

    • Thanks, Gustavo — it’s been corrected in the article!

  • Deidre Mercer

    This verifies why my grandparents, when ever meeting any of my friends, started the conversation with: “where are your people from?”
    My grandmother was a descendant of The Hairston Family the largest family in America.

  • Michael Hinsley

    This is so exciting!

  • Belinda

    I don’t find that at all surprising. I’m a fourth-generation Australian but I have nearly a thousand cousins in the 23andMe database and most of them live in the United States. None of my ancestors ever lived in America – they all came from the British Isles and Germany, so the links must go back to the Old Country (whichever one that might be). My sister and her husband also have about that many cousins here, though many of my sister’s are different to mine, and of course her husband’s are different again. I’m no longer surprised at who my relations are and I welcome them all into my family.

  • Glenna

    Many years ago I hitchhiked all around the United States and made a habit of making conversation around connections and almost always would eventually find one with these random people. I did this both because it was interesting, but also as a safety device: establishing a relationship, even by distant-cousin-marriage, made you family.
    In all, a great experience, although were I young again I would not do it now.

  • Martha

    Belinda, you and your sister have different “dna cousins”? THat doesn’t seem like it should be possible. I know siblings have slightly different DNA of course, but it shouldn’t be so different that it changes, well, who you are related to. All this makes me suspect this DNA connection as not being very true. 23andme, what do you have to say about this?

  • Ponto

    Siblings are about 50% similar to each other. That sounds quite a lot but half of their dna is not shared, and it is not surprising siblings would share with others and not each other in their half that they don’t share with each other.

    23andMe needs to do more to get the message out: Your genetic relatives are a small part of your genealogical relatives, those relatives you know from paper trails are your relatives but with whom you share nothing other than a couple of distant relatives in your family tree. It would save confusion when one’s 2nd cousin shares some dna with one sibling and zilch with another sibling.

  • Imre

    it is not true:
    “Indeed that notion that any two people – a cop in New York and a street vendor in Mumbai, say – could be connected through five other people was first written about by Stanley Milgram”


    “Karinthy has been regarded as the originator of the notion of six degrees of separation”

    ” Karinthy was the first proponent of the six degrees of separation concept, in his 1929 short story, Chains (Láncszemek).”

  • Charlotte

    I am 1/2 Williams and1/2 Stirewalt. That means I SHARE DNA with Some cousins from both my mother’s relatives and my father’s. I Don’t necessarily share Any DNA with my cousins. This has been quite hard to teach. It all depends on the luck of the “draw.” I have two of my four sibs on 23andme. Much of the Shared DNA we have, is shared by all three, but not everything is shared with all three of us, and some is not evident at all with the other two sibs And we share many different genetic cousins. This has made genetic study fun!

    What I find interesting is that I Look Like the combination of BOTH my grandmothers! And both sides have commented on this since I was very small. One was half French and the rest super early colonial roots of EnglandScotland, Ireland and Wales. raised in the Northeast. The other was a blend of early Scotch-Irish, German and some we don’t have figured in yet. Raised in the South. They looked like they could have been second cousins ( the more I learn about DNA the more they may have looked like First cousins). Their phrasings and speech patterns were similar, their handwriting was similar. That folks would see me as a blend is really a tribute to the DNA I received.

    And the more I discover my 3rd cousins, through, 23and me, and through sheer luck (paper trail and or DNA), the more I discover that my Williams cousins seem to have a dominant “look.”. Blue eyes are dominant, whether we received the brown hair genes or the super-almost-albino genes of the family.

    Recently I have decided that perhaps the auto-immune issues I struggle with come through my Williams genes. I have found others of my Williams relatives share RA, PsA, Ankylosing Spondylitis, Fibro, learning disabilities of Autism or Asperger’s and other auto-immune based challenges So far none of this seems to come out in my Stirewalt cousins. And a few might yet. But it does seem to suggest I look closer at my northern side for the genesI received. I am Sero- Negative, wish 23and me would do the HLA27 test. Genes SO FAR discovered do not give me any answers; mostgarments state normal range. I ask ALL of my cousins doing any type of DNA studies to share their results with me. Most do. Maybe we can find some of the other avenues that lead to these to manifest.

    My music, art and theatre genes are strong in both families. Many of us have more than one of these talents. Wth the luck of my “draw” my DNA gave me passion, talent and fun in all of these. What wonderful luck! Though I prefer to see a Master’s hand in it

    Great article! Keep up the good work.

  • Charlotte

    Ouch. The IPad struck again. Feel free to rephrase where necessary. I said. ” most of my genetic results” state normal range.

  • I don’t really trust any such services. Iam not saying you or any services similar are not able to help people find their ancestry,but ithink most have you paying a seemingly reasonable price in the beginning but it adds up as they supposingly continue in their quest to find more information. In these hard economic times most people cannot afford to continue the research and are left dissappointed. I do know from the little that i’ve been told that i have a colorful ancestry. My great grandmother was chinese. Iam african american,she married a african man with the surname “Larkin” but yet it’s an Irish name,weird right? So I will just wait until God’s newworld and find out more about them.

  • Bailey

    As an anthropology student, I find this very interesting. In fact, several bio-statisticians and computer scientists have told me that almost any two people on Earth can find at least one common ancestor 500 years ago. I wonder if this has any relevance to that. What does anyone else think?

  • varlene

    Milgrim was was corrected to Milgram in one sentence but is still incorrect in the one that immediately follows it.

  • stebuswork

    Many of the commentators are making the common mistake of saying they do not share “any” DNA with another person, or that the DNA match between siblings is only 50%, things of that sort. That is incorrect. We share over 99% of our DNA with each other, but it is possible to distinguish one person from another genetically in only one percent or so of our DNA. It may be true that within that one per cent we share only 50% of our DNA with a sibling; but the point of the show is that we are all interconnected much more than we realize.

  • pedro lank

    im, i connected, im pretty sure, that i share much of my dna with mi sibling &more than prbable with people of other in whatever region in the world from where me and the others family members sibling etc.como from whatever areas of that wor we happen to have ancestor ….who are they….? i dont now yet but i woul like to findout

  • bjt

    I wish this was true for me. Only child. Mother only child. Father only child (his father died when he was 3 months old) mother later remarried and had daughter (two marriages no children) and son (5 children).
    Mother’s mother had 2 sisters – one no kids. Other one boy. He had 3 sons. Middle one died young from brain tumor (same thing that killed his mother) but did leave behind a son. I have zero relatives with my last name genealogically related to me on the face of the earth. I have my father’s geneaology going back 7 generations before him. I’m barely here twice. Great, great, great, great, great grandfather died before only child (son) born. Then my grandfather dying 3 months after my father’s birth. Then my parents were married for 10 years before my mother conceived for one and only time resulting in me. So I think it would probably take many many links back to find a possible geneaological relative with my last name.

  • Jerald Gross, Major (Retired)

    I just received my test results and noticed that host Professor Henry Louis Gates, Jr and I share DNA from the same subgroup. When are you going to showcase ordinary citizens?