The DENNISON Surname Patrilineages Association (DenSPA)

DenSPA and the DENNISON Patrilineage Projects

The DENNISON Surname Patrilineages Association is comprised of a set of independent DENNISON Patrilineage Projects.

One of the key concepts in genealogy is the genealogical patrilineage. This is because in most modern societies the public documentary records that constitute the principal body of genealogical evidence identify males and unmarried females by their hereditary surname, which is passed down in the patriline from father to son to son....

Also passed down from father to son to son..., virtually unchanged, is the male-only Y-Chromosome, and since the early 2000s, when the pioneer testing company, Family Tree DNA, introduced their 37-marker ySTR test of certain areas of the Y-Chromosome, it has become possible through this yDNA testing to uniquely and conclusively identify the patrilineage of every tested male, and therefore to create genealogical patrilineage projects all of whose members know for sure that they descend from a common patrilineal ancestor.

The DENNISON patrilineage projects to which the links at the top left of this page refer, are the cultivated fruits of this possibility. These projects and their umbrella association, DenSPA, have no affiliation with FTDNA or any of its surname projects, including the FTDNA DENNISON Surname Project—even though one of the criteria for membership in DenSPA is to have taken, or sponsored, an FTDNA 37-marker ySTR test either of a male who is himself surnamed DENNISON, or of a male whose resulting test haplotype matches that of an existing DENNISON patrilineage.

Each of these patrilineage projects has been organized for the purpose of bringing together in one place all the best genealogical research and researchers of the patrilineage, to encourage and facilitate active and possibly collaborative research on the part of the members. To best accomplish these ends, these are open public projects, and members are required to provide both their raw yDNA results and an ancestral pedigree back to their earliest documentable ancestor, and to consent to the publication of this information on the project web pages, backed by their names and a current email address. This contact information is essential to the whole cooperative spirit and open nature of these projects, as it allows each of the member experts in their particular sub-branch of the patrilineage to be contacted both by other project members, and by other genealogists interested in the patrilineage who might want to test and join the project themselves.

Because these patrilineage projects are essentially genealogical projects (unlike the FTDNA surname projects, which are now just places for tested males to anonymously park their yDNA result haplotypes), the members of these patrilineage projects aren’t necessarily the tested males themselves. Rather, each member is the designated “principal genealogist” representative of a particular tested male’s ySTR haplotype. A member may thus be either the person tested or a female (or male) relative who has commissioned the test and obtained the permission of the test subject to use his haplotype within the project guidelines to elucidate his (and their) patrilineage ancestry.

Since these haplotypes don’t sample any part of the genome with known genetic function, and are thus indicative only of membership in a broad patrilineage group descended from a common patriarch who lived many hundreds of years ago, there is no reason why any male DENNISON who is interested in his ancestry, and/or sufficiently sympathetic to the interest of a genealogist relative to test his yDNA test for him or her, should have any qualms about publishing a list of from 37-111 ySTR numbers derived from his Y-Chromosome. There is, however, a small chance that ySTR testing might determine that somewhere up the ancestral chain there has been an NPE (Non-Paternity Event)—a divergence between the surname and the biological patriline. The corollary of a famous line from Shakespeare is also true: it's a wise child who knows his own father.

The DENNISON Patrilineages and the Surname they share

Each of these individual patrilineage projects has its own stand alone project web pages, and there is no more reason to suppose that any two patrilineages that share a common surname are any more closely related to each other than, say, a JONES and a SMITH patrilineage chosen at random.

However, since the members of these unrelated patrilineage groups do share a common surname (possibly with characteristic spelling variants), their research stands to benefit in comprehensiveness if they take the time to familiarize themselves with the genealogies of the other patrilineages, particularly when these overlap in spacetime.

And since adequately comprehensive research typically requires the compilation of abstracts of many, or even of all, of the records of a certain class that pertain to a particular surname, the comprehensive research of a member of one patrilineage may benefit not only his own patrilineage cousins, but also the researchers of other, unrelated surname patrilineages. It is for this reason that a number of such comprehensive abstract collections and other trans-patrilineage genealogical resources for the surname DENNISON have been published under the DENNISON Genealogical Resources & Evidence heading in the upper left navigation panel of this page.

There’s a home here for all DENNISON researchers who’ve sponsored a ySTR DNA test

I was the original founder and administrator of the FTDNA DENNISON Surname Project, but I feel obliged to resign that position now that FTDNA has voluntarily imposed a set of crippling restrictions on their projects that represent their poorly thought out interpretation of the new GDPR regulations imposed by EU bureacrats on citizens of member countries, in the name of the long vanished possibility of internet privacy.

FTDNA Project administrators are now forbidden from publishing the test results of their project members in association with their names or contact information. These regulations make it impossible to organize fruitful surname or patrilineage projects, and thereby largely obviate any genealogical benefits to serious researchers of ySTR DNA testing. Consequently, only by severing these DENNISON patrilineage projects from the FTDNA DENNISON Surname Project, and terminating my own association with the latter, can I and the members of the DENNISON patrilineage projects that I administer continue to exploit the unique opportunities that such projects offer for focused collaborative genealogical research.

As for the supposed danger of exposing an individual member’s ySTR DNA haplotype, since their haplotype merely samples a tiny portion of the Y-Chromosome that has no known genetic function, the only meaning to be derived from the string of two digit numbers that make it up is that the person tested belongs to a patrilineage whose common ancestor lived, in most cases, many hundreds of years ago. I dispense with other aspects of FTDNA’s spurious rationale for imposing these restrictions here.

For as long as FTDNA continues to offer their ySTR DNA tests and genealogists order these tests for DENNISON males in the hope of advancing their genealogical objectives, I shall continue to act as an independent advisor and coordinator of DenSPA and the DENNISON patrilineage projects that collectively offer a home to all qualifying researcher members. The terms and requirements of membership are spelled out in more detail in the “To Join this Project” section of each of the DENNISON patrilineage projects for which links are provided above.

The final patrilineage project link above, Singleton DENNISON Patrilineages, points to a catch-all page for DenSPA members who have as yet no patrilineage matches. If and when at least one other match to one of these Singleton members turns up, a separate independent patrilineage project page will be created for them, provided that the match isn’t to a known close cousin (there is little or no point in ySTR testing known close cousins for the simple reason that their genealogy is already known).

One can order a qualifying 37-marker Y-Chromosome (ySTR) DNA test directly from Family Tree DNA, but (except when one of their sales is going on) a better price ($149) can be obtained by ordering a test while joining one of their surname projects. For example, one can apply to join the FTDNA DENNISON surname project. Then, once the test results are in, just notify me by email. The “Email JBR” button in the upper right corner of this page should open up an email blank addressed to me.

The DENNISON Surname: Etymology, Origins, and History

Although I’ve adopted DENNISON as the generic spelling of this surname in all my writings and DNA projects, the surname actually appears to have two derivations, one with a “t” (DENNISTON—the Scottish spelling), and one without. The reason I’ve used just DENNISON to stand for both forms is that until spelling was standardized in the early decades of 1800s (when Webster's Dictionary became a best seller, with it’s novel principal of one correct spelling for every word) spelling of all but the most familiar words was phonetic, and subject largely to the idiosyncratic ear and experiential background of the recording clerks. If these were more familiar with the Scottish spelling they might “correct” what they perceived as the mispronunciation of their subjects, and slip in a “t”, while if their background didn’t expose them much or at all to the Scottish usage, they might elide the “t”. The 1901 UKCensus for Scotland suggests that the same process of erosion may have taken place there, because the “t”-less forms are far more prevalent by then even in Scotland.

However, for purposes of the following etymological and historical discussion of the surname, I shall differentiate these two surname strands as DENNISON and DENNISTON.

Reaney & Wilson’s etymological A Dictionary of English Surnames (Oxford University Press, 2005) also has two entries for this surname specifically in England, even though both forms are primarily associated with the more Celtic ethnic areas of Britain: Scotland, Ireland, Wales, and Cornwall.

The Late Surname Adoption Factor

Surnames began to be prevalent in England early, in the 1300s, because that was the century of the Black Death, which killed at least a third of the population and set another third onto the road as refugees in search of safety and sustenance when their local communities collapsed around them. But in the rural outlying Celtic areas, many families and individuals deferred adopting surnames until the 1700s or even the 1800s—whenever it was they out-migrated. And when they did choose surnames, besides carrying over their occupational or locational bynames, they favored two other approaches in creating or selecting surnames: (1) they fashioned patrynomic surnames, like Scottish Mac’ or Gaelic O’ or English “-son” appended to their father’s given name or surname; or (2) they took on the surnames of local lairds, landlords, or other esteemed local dignitaries.

NPEs Add Surnames to a Patrilineage, and Patrilineages to a Surname

The other major cause of shallow surname lineages that go back fewer than ten generations are Non-Paternity Events (NPEs). In any given generation there is a small chance of an NPE occurring, and these chances accumulate with the generations. A typical average NPE rate for American immigrant groups before modern times would be 2% per generation, but there is reason to believe that back home the rate was higher (perhaps as high as 5%), particularly in the ethnic Celtic areas, which seem to have taken a more relaxed attitude toward extra-marital sex than the emigrants, who tended, at least during the American colonial period, to be more conservative and religious than those they left behind; and even at 2%/generation, the chances that an NPE occurred across ten generations would be about 18%.

Scottish and Scotch-Irish (Ultster Scot) DENNISTONs

The DENNISTON version of the surname derives from an ancient Scottish gentry landowning family that has been traced back to at least the 13th century, and which at one time had ties to the royal STEWART line. The earliest forms of the Scottish name were apparently Dennistoun (or in Latin, the language of the literate, Danzielstoun, which was probably also the name of the Renfrewshire town from which they hailed, or in which they were predominant). This Dennistoun reference, which is partly etymological, and partly heraldic, is derived from the definitive (but not necessarily always correct) George F. Black, The Surnames of Scotland (1999).

This surname distribution map based on the 1881 UKCensus shows DENNISTONs clustered along the west coast of Scotland in the adjacent counties of Renfrew (supposedly the locus of the original Danzielstoun), spreading out from there to Lanark (with its great port city of Glasgow), and north across the Clyde Estuary to Dumbarton (where the principal later DENNISTON estates were located), Stirling and Argyll. A second and even greater concentration is found in Kirkcudbright, and adjacent Wigtown, but this lot appears to be of quite independent origin, since there are virtually no DENNISTONs in the intervening counties of Ayr and Dumfries.

DENNISON Patrilineage 1, the largest yDNA tested patrilineage, descends from this Scottish DENNISTON gentry line, although the majority of DENNISTON immigrants to Britain’s North American colonies came via Ireland, where a branch of this patrilineage was established in the early 1600s. The original Irish DENNISTONs had commercial as well as landed interests, and thus were found to some extent in Dublin and Belfast, though their lands lay primarily in an area of north central Ireland centered primarily on counties Longford and Leitrim. However, one branch of Patrilineage 1 DENNISTONs also appeared in Ireland’s south, in Cork, county Munster, and this line apparently had commercial ties also to Wales, across the Irish Sea.

Reaney & Wilson’s entry for English DENNISTON offers four instances of the surname: Henry de Denneston (on an 1199 Staffordshire assize roll); Hemfrey de Denarston (1275, of Norfolk); John Denston (1453, of Essex); and Robert Denstone (1641, on a Somersetshire petition). It also suggests that the “Denston” form of the name may have derived from Suffolk and the “Denstone” form from Staffordshire. But even though the gentry Scottish DENNISTONs had wide-ranging commercial interests that may have placed some in the ports of London, Bristol, or Liverpool, I doubt that any of these cited Englishmen besides possibly Henery de Denneston of Staffordshire, were of the Scottish DENNISTON tribe. Henry was an early favored Welsh given name (the English kings of that name were of Welsh extraction), and Staffordshire almost borders Wales.

A sprinkling of DENNISONs appear in the UKCensus of 1881 in some of the same areas of Scotland as the DENNISTONS, but most of these instances are probably cases where the “t” sound eroded phonetically over time, and original Scottish “Denniston” spellings were crystallized out as “Dennison”—just as they sometimes were in the areas of transmontane colonial Pennsylvania and Virginia where the Scotch-Irish immigrants to America primarily settled. However, I note that the Scottish Kirkcudbright and Wigtown contingent all seem to have held on their “t” since none appear on the DENNISON Surname Distribution map.

How do we account for the fact that there are several different patrilineages in which the DENNISTON spelling has persisted, in at least some branches of the patrilineage?

Most of these instances probably arose due to late surname adoption in the Celtic areas of Britain. To recapitulate: many families and individuals in the Celtic areas of Britain, including Scotland, were late to adopt permanent hereditary surnames, and they only did so on the threshold of out-migration. When they made their choice of surname, they often selected the name of a prominent local family, perhaps their laird or landlord. Interestingly, we find this same pattern of assuming the master’s surname among the freed black slaves of the post Civil War South.

A secondary cause for the proliferation of the DENNISTON surname might be a rather common type of NPE in which an unmarried DENNISTON female bore a bastard child whom the father was unwilling to acknowledge. By law, such children were given the surname of their mother, and perhaps also a special incentive to out-migrate from the local community.


Reaney & Wilson’s entry for English DENNISON provides a few early examples of this form, all, as it happens, from eastern and central counties: Roger Deneyson (no date, from a charter roll of Norfolk); Adam Deynissone (1381, on a subsidy roll of Suffolk); and Henry Dennesson (1450, Cambridge records). These forms are thought to be derived from “son of Denis” (the early spelling of this given name). A second derivation is suggested for Walter Denizen (1275, of Essex), possibly derived from the AngloFrench (Norman?) deinzein—a burgess, or accepted citizen of a town. That’s as it may be, but I note that one finds “Denizen” as a phonetic spelling variant as late as the 1800s in the Americas.

The surname frequency statistics that I’ve worked up show that DENNISONs were actually more prevalent (adjusting for population) in Great Britain (England, Wales, and Scotland) as a whole, than DENNISTONs, but (contrary to the earliest loci of this English surname) the DENNISON surname distribution map for 1881 shows that English DENNISONs were clustered predominantly in the northeast of England, in the counties of Westmoreland, Cumberland, and Yorkshire West Riding. These counties virtually border SW Scotland, but the DENNISON surname almost certainly has an entirely different derivation than DENNISTON, with its association with the ancient Scottish gentry family of that name.

The surname “Dennison” is one of a class of patronymic surnames that are derived by appending the suffix “-son” to the given name of a young man’s father to create a surname for the son. As I’ve noted elsewhere, the high period for surname adoption in England was the mid to late 1300s, coincident with the Black Death, and according to R.A. McKinley, A History of British Surnames {111-112}, surnames ending in “-son” became especially prevalent during this early period in Yorkshire in particular, and in the northeast of England in general, and this probably accounts for the majority of the purely English DENNISONs.

Native Irish DENNISONs

Today we think of Dennis as a characteristically Irish given name, which is in line with the evolutions of Christian history. According to George Redmond, Christian Names in Local and Family History, Dennis is a given name derived from the 3rd-century bishop of Paris, St. Denis (the patron saint of France, but a non-scriptural saint), and as such had modest early currency in England as well as in persistently Roman Catholic Ireland. However, since Denis/Dennis wasn’t Biblical, it all but disappeared from England and Scotland after the Reformation. Of course, the naming of children has always been influenced by fashion and certain names sometimes acquire a local vogue. Thus, Redmond {57} tells us that when one William Oglethorpe sold off property in 1596 in Kildwick, Yorkshire West Riding, no fewer than nine men of different surnames had the given name Dennis. By that time, as noted, virtually all Englishmen had surnames, though many, if not most, locally fixated Irishmen and Scots did not.

Most residents of the Celtic areas of Britain, were slow to adopt permanent hereditary surnames, because they didn’t need them. For the most part, extended British families and their descendants lived in the same local neighborhoods, hamlets, and villages for century after century, and to differentiate the local Johns it was sufficient to refer to them with bynames that perished with their bearers, e.g. John Bridge for the John who lived near the town bridge, or John Smith, for the local blacksmith. In these areas a tiny landed gentry class (many of them English absentee landlords) owned all the land, and most of the rest of the population were virtually serfs tied to long or lifetime leases of their land—or they were local artisans whose survival was comparably tied to their local custom and patronage. It was only when the occasional family migrated to a city or substantial town, or a different country—or when a young man just ventured out of his area in search of work, that it became necessary to assume a surname to uniquely identify the migrants in a new area where they weren’t known.

The counties of NE England where DENNISONs clustered in 1881 are a short distance across the Irish Sea from the ports of Belfast and Dublin, and ships or packet boats have been plying between these Irish ports and Liverpool in Lancashire for many centuries, conveying large numbers of poor landless (and surnameless) Irish laborers to England in search of work—but particularly during the Industrial Revolution, when cities like Leeds, in Yorkshire West Riding, underwent spectacular growth on the back of the cloth manufacturing industry. Given the popularity of the given name Dennis in Ireland, it’s likely, therefore, that some of these Irish immigrants adopted DENNISON as a surname, and many of these will have carried this surname back to Ireland, which remained their permanent home.

Thus by these lights, Ireland, from whence the vast majority of British emigrants to America embarked, was populated by the 1700s both with Scottish-origined DENNISTONs and by native Irish with the anglicized surname DENNISON—although by the end of the 19th century, the spellings of these two different surnames had largely converged on "Dennison" or "Denison" everywhere but Scotland, as my surname frequency statistics show.

DENNISONs to America

There is one smallish cluster of Dennisons that appears on the 1881 surname distribution map for England, which is worth making special note of. Quite a few Dennison families are found in 1881 in several towns of the eastern county of Essex, fanning out into the adjacent inland counties, of Cambridge and Hertfordshire, an area that was a fountainhead of much of the early 17th-century Puritan migration to New England. And sure enough, it turns out that the first known American immigrant bearing the DENNISON surname was William Denison of Hertfordshire, who emigrated with his family in 1631 on the Lion to Roxbury, in Massachusetts Bay. These families may have drifted down from Yorkshire, or even from Scotland, or this line may have had an independent local origin, perhaps from one of the other derivations suggested by Reaney.

The surname DENNISON was next brought to America in the early 1700s by Scotch-Irish settlers. More often than not the name was spelled “Denniston” (with the “t”) among this contingent, betokening its Scottish origin. And so far, all of the tested members of the DENNISON DNA Project for whom the name is sometimes spelled this way in the records, are of the same Scottish DENNISON Patrilineage 1; and further, virtually all or the known 18th century immigrants of this patrilineage settled on the transmontane western frontiers of Pennsylvania and Virginia—the most popular destinations for the Scotch-Irish who immigrated to England’s Thirteen American colonies in large numbers from 1720-1775, and at a slower pace after the Revolution.

However, by the time of the 1820 USCensus (the first that was substantially complete for all states) despite the early clustering of Scotch-Irish DENNISONs (with a “t”) in SW Virginia, no fewer than 298 households were headed by “Dennison”s or “Denison”s (without the “t”) and these are overwhelmingly concentrated in New England and New York! Even more surprising, perhaps, some 20 of the 30 DENNISON householders whose name was spelled with a “t”, resided in New York. It is known, as a matter of fact, that some of these New Yorkers belonged to the Scottish DENNISON Patrilineage 1, but overall this prevalence of New Yorker DENNISONs (both with and without the “t”) is an unexpected finding and it will be interesting to learn more about these lines when their descendants find their way to the DENNISON DNA Project.

As for the New Englanders, some of these are probably descended from the very early William Denison of Roxbury in the Massachusetts Bay Colony, who brought over sons when he arrived in 1631, and there was also a John Denison, early settler of Ipswich in Massachusetts. But I suspect that a few of these New England DENNISONs may have derived from the smaller early 1700s Scottish and Scotch-Irish settlements in frontier New Hampshire, and in a couple of townships on the southern Connecticut coast. I myself have immigrant Scotch-Irish ancestors from both New Hampshire and Connecticut, as well as from Pennsylvania and SW Virginia. At any rate, once we have accrued some project members from these other lines of American DENNISONs, we should be able to assign them to their respective patrilineage and begin to sort out the broader picture of DENNISON immigration to America.

Finally, the story of DENNISONs in America wouldn’t be complete without the descendants of the several immigrants to Canada in the 1800s, all of them from Ireland, and all of them proven by yDNA testing to belong to the ancient Scottish-origined DENNISON Patrilineae 1.



Navigating from here

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Distribution of the DENNISON Surname in Britain & the US

MAPS of DENNISONs & DENNISTONs in Great Britain, 1881

“Dennison” and “Denniston” are broken out separately in these surname distribution maps (created from Archer Software’s Surname Atlas), and I have capitalized the latter surname to indicate this. Elsewhere on this page, however, the ““Dennison”” spelling will be subsumed for convenience under the generic capitalized form DENNISON, because there is reason to believe that there is substantial overlap between these surnames that are nominally independent. If this seems a rather arbitrary compromise, it should be remembered that even if the generic spelling “DENNISON” were made to represent only surnames whose spellings crystallized out as “Dennison”, it would still represent a collection of many independent surname lineages.

It is suggested that the following maps be opened in pairs for comparison. To do this, right click each map link and select “Open in New Window”; you can then size and array the two map windows side by side for comparison, first minimizing the surname page if necessary.


DENNISONs in Great Britain, 1881, per 100,000 Population

DENNISTONs in Great Britain, 1881, per 100,000 Population


DENNISONs in England, 1881, Actual Numbers

DENNISONs in Scotland, 1881, Actual Numbers


DENNISTONs in Great Britain, 1881, Actual Numbers

(there are only 16 south of Yorkshire, mostly in London)


The Frequency of DENNISONS/DENNISTONs in Britain & the US

The original form of this surname, in many cases, was “Denniston”, derived from “Danzielstoun”, a large landholding in the ancient Scottish county of Renfrew, in the neighborhood of Glasgow. The proprietor of this land was a member of the Scottish gentry named Daniel, and the original form of the name “Danziels” is the Latin genitive for Daniel.

Many original bearers of this Scottish name have come to adopt “Dennison” or “Denison” in its place, but there is every reason to suppose that the form “Dennison” arose independently as a surname, with an entirely different derivation, perhaps as a patronymic of the surname “Dennis”. This is suggested particularly by the fact that the form “Dennison” is more common in England than in Scotland or the U.S.

The DENNISON Surname in Britain and the U.S.
Born between: 1881-1901 1880-1900
Surname(s) in: England Scotland United States
all names (millions) 13.5 2 34.3
Dennison 1303 117 2083
Denison 480 24 1462
Den(n)iston 36 46 456
---------- -----
TOTALS 1819 187 4001
Number of people bearing the generic surname DENNISON per million of population
Surname Frequency Index
1900      1997
England 134.7                 
Scotland  93.5                 
United States 116.6       106.8

The Surname Frequency Index (SFI) for 1900 was derived by dividing the number of people with the generic surname DENNISON (including all the above listed spelling variants) who were born during the 20 year period immediately preceding the census for each country, by the total in millions of population enunmerated in that census.

The SFI for the US in 1997 is based on a database of listed telephone subscribers, as reported in Hanks’s Dictionary of American Family Names.

The SFI is only a surrogate for the actual frequency in each country of the generic surname DENNISON compared to other surnames, but it is the best measure of surname frequency I can conceive and readily compute. Any attempt to estimate the total number of surnames in existence must also take spelling variations into account. But who, in the end, can definitively say, for each surname, which are its variants, and which are independent surnames, or variants of other names? Thus, both the numbers that go into this SFI calculation are formally indeterminate. However, the variants chosen for sampling here as DENNISONs were carefully considered, and based on extensive experience in searching for these names in the records, and I believe that they account for at least 98% of the names that can reasonably be considered spelling variants of DENNISON in the countries of Britain and its erstwhile empire.

More importantly, as I have tried to indicate above, when I speak of the surname DENNISON, I speak knowingly of a hybrid. Not only do I expect there to be derivations of the name other than from the Scottish place, Danzielstoun, I also expect the name to have arisen independently in several, if not many, different families, just as most surnames have done.

"Dennison" (but not the other variants that comprise DENNISON) was the 1527th most common surname as of 1964, according to the Social Security data for that year, as reported in American Surnames.

Elsdon C. Smith, American Surnames (1969; reprint GPC, 1994)
Patrick Hanks, Dictionary of American Family Names, 3 vols
   (Oxford University Press, 2003)

Estimated Years to Convergence (TMRCA) of DENNISON Patrilineage Pairs

Each cell of the following matrices contains an estimate of the number of years ago that the common ancestor (the MRCA) of the pair of DENNISON patrilineages defined by the intersection of row and column walked the earth (the unnumbered patrilineages, with just D-membership#s, are unmatched singleton haplotypes). There is an equal (50%) chance that the time to convergence is less than the estimated number as more, but these estimates are very rough, and could be off by as much a couple of centuries either way. Taking the extreme case of two identical haplotypes, the estimate for the same 50% confidence level would be 60 years (plus or minus) back to the MRCA, but higher confidence levels (that the estimated number wasn’t too low) for identical haplotypes would be: 90%= 150 years; 95%= 210 years; and 99%= 300 years.

These estimates improve, the more markers that are tested, and when the time to convergence is less moving from 37 to 67 markers, it can be expected to tighten further when moving to 111.

Years to convergence based on 37-marker comparisons                             Years to convergence based on 67-marker comparisons

TMRCAs of DENNISON patrilineage pairs, based on 37-marker yDNA haplotypes TMRCAs of DENNISON patrilineage pairs, based on 67-marker yDNA haplotypes


The number in each cell is the estimated number of years back to the MRCA for the pair of patrilineages defined by the intersection of row and column.

Thus the lowest numbers represent the closest relationships.

Color-coding shows whether a haplotype pair Definitely, Probably, Possibly, or Just Possibly belongs to the patrilineage.

However, the color-coded categories don’t take account either of the common surname that all of these haplotypes share,
     or of the possible convergence of their genealogical evidence at a particular time and place. And where either of these conditions obtain,
     the relationship falls in the possible ranges, and when surnames may have originated that far back, the paired patrilineages may be one.

Last updated 9Mar2023
© John Barrett Robb
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