Detecting Mayflower DNA

Jayne Ekins

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Can DNA tests detect “Mayflower DNA?” This Thanksgiving story looks at early intermarriage and pedigree collapse among early Pilgrims in New England and the possibility of DNA founder effect—and what this means for genetic detection of Mayflower roots by descendants.

I used to be in the club of proud Mayflower descendants. But I’m not anymore. Apparently news travels slowly, because the fateful blow was dealt in 1936, and my family only just conceded 5 years ago.

My grandmother was an eastern “American aristocrat” who ran away from her family and married the son of a coal miner in the desert west of the United States. At their passing, I inherited a box of priceless documents and pictures of my grandmother’s privileged upbringing and her beloved relatives, most of whom I knew nothing about.

Portrait of William Brewster. Credit and license: Wellcome Collection CC BY 4.0.

Portrait of William Brewster. Credit and license: Wellcome Collection CC BY 4.0.

Among her lineages is the surname Brewster, which had been proudly and professionally traced back to William Brewster, ruling elder of the colony at Plymouth. My relatives made pilgrimages to historic colonial sites in Massachusetts, and my grandparents even named their first-born son Brewster.

Except, it turns out William Brewster isn’t our man after all. Whoops. Twentieth century research that evaded my family’s attention establishes that our Nathaniel Brewster, a purported descendant, was actually unrelated to the Mayflower passengers. The fact that he was instead a member of Harvard’s first graduating class of 1642 has been our sole consolation since being handed our hats at the Mayflower club. Harvard will have to do.

The General Society of Mayflower Descendants was founded in 1897 to honor Pilgrim ancestors, keep their stories alive, and facilitate connection among their descendants worldwide. Membership is strictly limited to those who can provide proof of lineage to one of the passengers who traveled on the Mayflower in 1620. And did you know, there are a lot of Mayflower descendants?

Pop Quiz: How many Mayflower descendants are projected to be in the world today?

  1. 35,000
  2. 350,000
  3. 3.5 million
  4. 35 million

Gold star for you if you chose 35 million! (Actually it’s 35 million, minus my family.)

A Little Mayflower Backstory

Cue dramatic music….

Four hundred years ago, the Mayflower dropped anchor at the tip of what is now Cape Cod, Massachusetts with 102 brave men, women and children searching for a new life of civic and religious freedom. They crossed the Atlantic during October and November of 1620, with harrowing mid-ocean storms that nearly disabled the ship, washed passenger John Howland overboard, and resulted in the death of the youth William Butten.

Storms pushed them to land far north of their intended destination in Virginia, and the immigrants encountered wintry conditions that were much more severe than they had anticipated. By the following spring only 53 of the original party were still alive. The staggering death toll was attributed to poor shelter, insufficient food, and disease that resembled a mixture of scurvy, pneumonia and tuberculosis. These intrepid families paid a steep price to blaze the trail for the cascade of immigrants that followed.

Connecting to Mayflower ancestors using DNA

Now 400 years later, we have a marvelous tool that is blazing trails in its own way. DNA has proved most useful in connecting present-day descendants to historical communities that existed hundreds of years ago. Might it be possible that one day a DNA test might be the entrance ticket to membership in the Mayflower Society? (And also the test to root out nefarious imposters such as myself?)

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Y DNA, mtDNA or autosomal tests?

Y-chromosome and mitochondrial tests are certainly useful for this question, and indeed Family Tree DNA sponsors both Y-DNA and mtDNA projects within its Mayflower: Official Project of General Society of Mayflower Descendants initiative. However, these two tests can only trace genetic ancestry on the strictly paternal or maternal lines. This means that to join, your genetic descent has to come down entirely through men or women (not a combination of ancestral genders, such as your mom’s dad’s dad’s mom, etc, which is much more statistically likely).

So what about autosomal DNA testing for Mayflower ancestry? Autosomal DNA does allow you to combine those male and female ancestral lines in your search for specific ancestral communities and relative matches.

AncestryDNA identifies genetic communities where ancestors may have lived in the last 8-10 generations (between, say, 1700 and 1975). With Mayflower action happening in the early half of the 1600s—perhaps 11-13 generations out from current descendants—this historical timing puts the original Mayflower families out at just the edge of resolution of currently used DNA markers and methods. Remember, this methodology is connecting you to a community, not a specific ancestor. Those are two different things. Even so, is it possible that autosomal DNA may have some power to identify modern-day descendants of the Mayflower? Let’s see what principles may be at play here.

Was there a founder effect?

In large DNA ethnicity studies like those developed by genetic genealogy companies, it is useful to look for genetic commonalities and differences found among groups of people. DNA signatures can be found that are distinctly identifying of a group of people. Biological mechanisms constantly at play influence how DNA changes over time within a group and provide these unique genetic signatures.

Founder effect is a term that describes the sharp decrease in genetic diversity that occurs when a smaller group breaks away from a larger group to form a colony:

Founder effect: The original population (left) could give rise to different founder populations (right). Public domain image.

Founder effect: The original population (left) could give rise to different founder populations (right). Public domain image.

In this case, Mayflower passengers broke off from the larger population of England to form an isolated colony, and they could only bring with them their personal genes rather than the broad range of genes that are found at large in the whole population of England. If the original Mayflower group remained isolated and had children only with other Mayflower people, the narrow genetic characteristics of the original founders would be magnified and accentuated in subsequent generations. The DNA of the descendants of an isolated Mayflower population would have genes that showed they came from England, but over several generations their DNA signatures would also develop specific characteristics that were particularly frequent in them. These distinct characteristics could persist even still today if they were firmly established.

In hypothesizing a Mayflower DNA test, the idea of founder effect would certainly be applicable and advantageous, but hinges heavily on whether the original population stayed isolated for long enough to produce conditions where detecting a founder effect is likely. If there were several generations of intermarriage without contribution from outside groups, that would likely establish genetic distinctness and also move that population forward in time to the point where our current genetic tests are considered to be sensitive. Restated in brief, if Mayflower pilgrims landed in 1620 and continued to strictly intermarry into the 1700s, a “Mayflower DNA test” could be a real possibility.

This isn’t what happened, though.

Of the 18 adult women on board the Mayflower, only four lived to see the first Thanksgiving a year later. Imagine the suffering of that year. There were already descendants from some of those women to keep the Mayflower gene pool going, but maintaining a new population with such an imbalance of men to women is not a likely prospect. And further, there was another boat in 1621. The ship Fortune arrived with 35 new colonists. In 1623 the ships Anne and Little James arrived with desperately needed supplies and 100 or so new settlers. Some of the new arrivals were family members of Mayflower passengers who were reuniting, so some of the gene pool of the Mayflower also came on other ships, but most of these people were unrelated.

In general, the travelers aboard the Mayflower and these other ships were from diverse locations in England. The separatists were part of a small but geographically broad movement where many unrelated nuclear families eventually immigrated together, accompanied also by unrelated individuals. A sister establishment, The Massachusetts Bay Colony, was founded in 1628 and brought new waves of settlers while immigration continued in earnest through 1643 until King Charles I effectively shut down the practice. Over this short time period, 21,000 English Puritans immigrated to New England.

Many of the original Mayflower passengers formed the leadership and established prominence that persisted as the social dynamics of the burgeoning colony developed. But they did not isolate. They regularly married people who arrived on other boats.

We can think of the likelihood of detecting a founding genetic signature of Mayflower colonists being heavily influenced by how diluted the genetic pool became through intermarriage with other settlers. This can actually be discretely examined generation by generation from the founding event. Even among the establishing generation, many individuals did not marry a Mayflower passenger.

Intermarriage among Mayflower descendants?

Of the 27 marriages that produced children in the founding Mayflower generation (I’ll call this generation 0), 16 marriages were between people that were either Mayflower passengers themselves or descendants of the passengers. There were 11 marriages where one of the spouses did not sail or descend from people who sailed on the Mayflower. Approximately 2 in 5 marriages served to dilute the original Mayflower gene pool, rather than preserve it.

In the next generation of people who descended from the original Mayflower passengers (generation 1 (G1)), 81 marriages produced children. Only 11 of these marriages were between people who both descended from Mayflower passengers. So in this generation, 7 in 8 marriages diluted the original Mayflower gene pool. There were not yet many marriageable cousins within the colony: marriage prospects were either siblings or people who were totally unrelated. An influx in colonists during this time broadened marriage prospects, and many took opportunities to connect with those people.

Familial intermarriage and pedigree collapse, which occurs when cousins or other close relations have children together, certainly occurred in the colony. This is seen to a greater extent in the next generation of colonists (G2). These are people whose grandparents were the original passengers of the Mayflower. Whereas in the previous generation, there was a decline in Mayflower-Mayflower marriages, there was actually an increase in G2 marriages between people who both descended from original Mayflower passengers, and an uptick in familial intermarriage. Perhaps the latter occurred in part because there were now cousins who were considered marriageable.

In the 450 marriages that produced children in G2, 1 in 5 marriages were between couples where both had descended from the original Mayflower settlers. But a further 4 in 5 marriages were between people where one did not descend from Mayflower ancestors. Despite the incidents of pedigree-collapsing intermarriage, the great majority of marriages served to dilute the Mayflower gene pool, rather than preserve it.

Pedigree collapse among Mayflower descendants

It would be a highly interesting exercise to examine the relatedness of marriages in subsequent generations to see if some Mayflower families continued to intermarry, and how long this practice continued. There are several instances in G2 Mayflower pedigrees. For instance, a set of 3 brothers married 3 sisters from another family, and the confluence of those relationships produced children who were double first cousins in G3 who descend from 4 different original Mayflower lines.

In these G3 or G4 micro-populations, the genetic characteristics of the original founders would strongly accumulate. Detecting this genetic signature today would be a matter of finding descendants of these highly intermarried Mayflower lines and searching for enduring distinct DNA characteristics. However, there are likely to be many more descendants from mixed Mayflower-nonMayflower lines just by the sheer force of outnumbering. The overall trend was that most people who descended from Mayflower lineages tended to marry people from other diverse voyages.

Now back to the question about Mayflower DNA….

So how does this bode for our question of whether there might be a viable DNA test developed to detect a distinct Mayflower genetic signature? With the information at hand, I’m going to say that it’s not likely. With the time frame of the Mayflower being on the suspected edge of resolution for our current DNA markers and methods, and with substantial mixing of Mayflower families with others arriving on different ships to the colony, a Mayflower-specific genetic signature is not likely to be found in our DNA today.

However, detecting a more general Puritan genetic community for the New England region could certainly be possible, as this population separated and continued to largely isolate for generations. This puts them into the time period that falls in the resolution time of our current DNA methods.

Autosomal DNA Testing for GSMD Entry?

This isn’t going to cut it, though, for people that are hoping for induction by autosomal DNA test into the General Society of Mayflower Descendants. For now, you’ll have to stick to traditional research methods to validate that noble ancestry.

And if you feel sad that you’re not allowed into this exclusive club, just remember that there are only 35 million members and I’m not one of them either.

Um, wait, I take that back. Maybe. As I was writing this last night, I logged on to FamilySearch to examine my defunct Brewster line, and saw a notification promoting a timely Mayflower initiative. The clickbait read “Discover your Mayflower connection! Your relative sailed on the Mayflower!”

At first, I thought the news of our family’s fall from Brewster-grace hadn’t reached FamilySearch yet. But inspection revealed that a different, under-examined line through my grandmother’s ancestry arrives 12 generations back at William Bradford, Mayflower passenger and Plymouth governor! Assuming this lineage is accurate, which I need to verify, I suppose our family pride wasn’t in vain after all. But maybe my grandparents should have named my dad Bradford instead of Brewster.

Want to learn more about what your DNA can tell you about your origins? Check out our free guide on DNA and ethnicity!

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<a href="" target="_self">Jayne Ekins</a>

Jayne Ekins

Jayne has been in the field of genetic genealogy since its beginnings as part of the Sorenson Molecular Genealogy Foundation. She has lectured throughout the United States and international venues on the applications of molecular biology to elucidating ancient and recent genealogical connections. She has authored and co-authored many peer-reviewed scientific publications, as well as general articles on genetic genealogy. It is a pleasure for her to see the accelerating developments in genetic genealogy, and the wide accessibility and application it has for the average human curious about their origins.


  1. Barb

    Thanks for posting this. It is an intriguing article, providing much to ponder while answering that question I’ve had about Mayflower DNA.

  2. Gayle

    Loved your article–read it out loud to my son. I got the same FamilySearch clickbait that you did–mine was for the Chilton family passengers. Research into the provided tree proved that it was faulty. My son bought me a beautiful framed Mayflower landing print for Christmas before I finished the disentangling of the tree errors. But hey, we share DNA with descendants of Frances Cooke so all is not lost!

  3. Daniel Symonds

    Wouldn’t you be able to use mitochondrial DNA to known mitochondrial DNA of the surviving 14 females?

    • Diahan Southard

      Right! Yes. We do mention that in the article, but it is limited in that it is limited to just choose who are lucky enough to share a direct maternal line.

  4. Cherie

    Genuinely no matter if someone doesn’t understand afterward its up to other users that they will assist, so here it happens.

  5. Bill Kempton

    Read your interesting article on Mayflower DNA and autosomal DNA or atDNA. I have eleven proved Mayflower descendants with three applications still in progress with the GSMD.
    I don’t have any formal training in genetic genealogy but don’t totally accept your conclusions about atDNA and its inability to determine Mayflower descendants. I am a twelfth generation all-male descendant of Ephraim Kempton who came in 1640 to Scituate, MA, which is confirmed by Y-DNA. I am able to discern Kempton relatives by atDNA matching with Ephraim’s children not in my line (total of 6) and grandchildren not in my line (total of 31). Although this is somewhat hearsay information but through the preponderance of data argument, I believe there is a way to use atDNA to discern Mayflower descendants.
    To test this, I am in the process of determining descendants of Mayflower passengers in my line through atDNA matches with those without collinear lineage interference. The results to date are promising. Perhaps when my evaluation is more complete will write a paper.

    • Diahan Southard

      I would be very interested in your findings. I think the problem, as you stated, is that you have to do a TON of genealogy to be certain there are no collinear lineage interference. It seems nearly impossible that you could find a group of Mayflower descendants that don’t also have a connection on another line (or two).

      • Bill Kempton

        You are correct about collinear lines generally being present in many early American ancestral lines and a very complete family tree is definitely required for a match evaluation. How much of an interference issue this can be is being investigated. However one of my most interesting observations is that, when a collinear line(s) is (are) present, the most recent shared common ancestor determines the cM value for my atDNA match. Obviously if this is true then my atDNA match with another Mayflower descendant requires the most recent common ancestor to be a Mayflower descendant rather than a collinear line.

  6. tom Fleetwood

    My ancestral lines are showing a fairly direct line to two daughters of Alden/Mullins and son Alexander of Myles Standish/Barbara Allen. Standish name is also showing up way earlier generations in England. Any benefit to DNA testing?

    • Danielle Francis

      Hi Tom, for ancestors this far back, autosomal DNA tests would not be much help. If you have a direct male line connection, you could use a YDNA test to learn more. Or if you have a direct female line connection, you could use mtDNA to investigate further.

  7. Jennifer Hickey

    I am so happy to have come across this & thank you for this wonderful explanation of Mayflower DNA. I have an application in with the GSMD but am stuck on one generation – there are no written sources linking a father (generation 6) and son (generation 7) in my proposed line, but my personal family history files indicate otherwise. This is on my paternal line. I am a female, generation 13. My father and I have both done Ancestry DNA & their Thrulines tool shows matches through this line. My question is – would it be worthwhile to have my father, who is still living, do a Y-DNA test with FamilyTreeDNA to see if there are any matches in their Mayflower Project? Or should I just give up? Thank you for any advice you can offer.

    • Diahan Southard

      The YDNA test would only be helpful in this case you have a direct male line connection from your Mayflower ancestor to your father (i.e. your Mayflower ancestor is your father’s father’s father’s father etc. going all the way back to the Mayflower). If one of the ancestors in the line to connect your father to your Mayflower ancestor is a woman (i.e. if it were your father’s grandmother who were a descendant of the Mayflower traveler) then your father’s YDNA results wouldn’t be relevant or helpful for this case.

  8. Dave

    I MIGHT be descended from Stephen Hopkins and daughter Constance Snow, supposedly thru her granddaughter Hannah Snow who married Hezekiah Doane, but it’s not proved that the “Hannah” who married Hezekiah is in fact Hannah Snow. However the Mayflower Society accepts applications from descendants of this line, due to “circumstantial evidence”, ie the Snows and Doanes were neighbors (in Nauset/Eastham), and Hezekiah and Hannah Snow’s parents (widower/widow respectively) married one another. I wonder if there could be some DNA workaround to prove that Hezekiah’s wife Hannah was in fact Hannah Snow…

  9. Ellen Hoffman

    I took one of your DNA courses, and used what I learned to review problems in my documented tree. I had good evidence from the Silver books about descent through several families (and partly multiples due to those intermarriages you talked about). I am neither an all male or all female line descendant so those existing projects are not helpful. What did come up was an issue with a more recent descendant where there was a dispute over parents five/six generations back. Hooray, atDNA to the rescue! I think this might even impact the later generations of the Silver book. So it may not be possible to go way back, sometimes it is enough to go back far enough.


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