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.
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?
- 3.5 million
- 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?)
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:
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 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!