The Black Death and downstream expansion of I-Y33765 -- Part 1: I-Y33765 in Somerset before 1348-9

One of the important benefits of Y-chromosome Next Generation Sequencing (NGS) analysis for the genealogist is that the technique identifies all the base substitutions or SNPs that have happened in the lineage of the man who has been tested. As discussed in earlier posts, by comparing NGS results for related men, and by using the estimated SNP mutation rate, we can calculate the Time to Most Recent Common Ancestor (TMRCA) or approximate date at which their most recent common ancestor would have been living.  At present seven men with the I-Y33765 mutation have NGS results and the age estimates for phylogenetically important mutations within the clade are shown in Table 1.   

Table 1: Single Nucleotide Polymorphism (SNP) age estimates for phylogenetically important mutations within the I-Y33765 clade.  Estimates calculated using the SNP mutation rate observed in the Nils Swensson pedigree.

One observation that can be made about the figures shown in Table 1 is the relatively late date we estimate at present for the expansion of both the English and Swedish arms of the I-Y33765 tree (for our latest tree see the post published 8 August 2021).  The three lineages so far identified in England having a TMRCA based on Y33767 of 1508 while for the several Swedish lineages the TMRCA based on FT250135 is 1650.  In this article, using English documentary sources, I will explore my idea that descendants from putative earlier branches may have been "pruned" by medieval plague events, in particular the Black Death.

The Black Death of the mid fourteenth century caused an unprecedented demographic trauma that halved the medieval population of Europe between 1348 and 1351.  Subsequent recurrent plague episodes restricted population regeneration for hundreds of years.  In England these "plague centuries" were those between the initial pandemic of 1348-9 and the mid seventeenth century when, for example, the "Great" plague afflicted London in 1665-6. 

Contemporary accounts suggest that a characteristic of the initial fourteenth century spread was that the disease was "non-selective" killing all social classes, all ages and both sexes with equal ferocity.  In Somerset the epidemiology during 1348-9 has been inferred from records for deaths of parish priests and the institution of a new priest at that locality.  

As I have explained before, I-Y33765 in England seems to be localized among men with the last name Clement whose male ancestry is within the Chew Valley, North Somerset. The Cult of St Clement and the conversion of Viking Age Scandinavian kingdoms to Christianity may have some significance for the adoption of this saints name by a male line with Scandinavian roots or this may just be an interesting coincidence.  Whatever the truth, the earliest recorded use of Clement as an hereditary surname in England occurs in Oxford in a charter dated 1153 by Agnes de Sibbeford, wife of Ralph Clement, which is witnessed by Hugo Clement and by William son of Richard Clement, who is later called Willelmus Clemens, with a brother Robertus Clemens (Reaney,1967). This charter is preserved in The Sandford Cartulary which was compiled in the second half of the 13th century, by order of Robert le Eascropp, Preceptor of the Sandford Templars in this period. It was transcribed by Agnes M Leys in 1938 for the Oxfordshire Record Society  and she describes it in her introduction as ‘the only complete record of the estates of any house of the Templars in England’ (Leys, 1941).

Here again,this connection between the Clement surname and an enterprise managed by the Knights Templar would seem an interesting coincidence since the earliest recorded use of the Clement surname in north Somerset is in two deeds which each mention lands at "Temple" Cloud in Cameley parish.  According to Faith (2009) "the Templars became lords of the vill of Cameley in 1201-2" and Mills (1991) suggests the affix "Temple" in the name Temple Cloud "probably refers to lands here held by the Knights Templars".  One of these documents is an undated marriage settlement drawn-up circa 1274 by Everard le Franceis for "all lands which I have in la Cloude in the parish of Cameley", which is witnessed by "Clemente de Cloude" (SW Heritage Trust; DD/HI/A/48/4) and the second deed is a grant, with warranty, dated 13 February 1283, for a fardel of land in Cameley to John Roger "Atete[m]ple" witnessed by William Clement (SW Heritage Trust; DD/HI/A/47/8) .  So, taken together, these two medieval deeds make it certain that the Clement hereditary surname was in use on the southern edge of Chew Valley in the second half of the thirteenth century. 

The 1327 Lay Subsidy Roll for Somerset (Dickinson, 1889) allows us to estimate the distribution of the Clement name in the county in the decades prior to the Black Death (red symbols, Figure 1).  At this time 60% of Clement name holders who were liable for taxation lived in Chew Valley, specifically in the contiguous parishes of Cameley and Hinton Blewett. The 1569 Certificate of Musters for Somerset (Green, 1904) gives a similar opportunity to estimate the distribution of the Clement name (green symbols, Figure 1) during the "plague centuries".   

Figure 1: Clement locations in Somerset before, and after, the Black Death, 1348-9.  Prior to the Norman Conquest it is my conjecture that the locus for I-Y33765 in England was the manor of Clutton (blue cross symbol) which was at that time held by Thorkel "the Dane".  From 1274 until 1347 thirteen medieval deeds document the Clement family living 1km south of Clutton at Temple Cloud in Cameley parish. The 1327 Lay Subsidy Roll records 60% of the Clement taxpayers in Somerset (red circle symbols) living in Cameley.  During the plague centuries documentary sources such as the 1569 Certificate of Musters record 80% of Clement militiamen (green circle symbols) living in parishes a few kilometers north and south of the parish of Cameley.  

The two medieval deeds mentioned earlier are included in two deed bundles among the Papers of the Hippisley Family of Ston Easton (SW Heritage Trust; DD/HI/A/47 & DD/HI/A/48) which contain 95 documents relating to property in the parish of Cameley which were written between 1263 and 1398.  Thirteen of these deeds, dated between 1274 and 1347, mention members of an extended Clement family who lived at Temple Cloud.  The earliest reference, to Clemente de Cloude, is in the fourth earliest deed in this collection and implies the family were in the parish of Cameley from at least the mid thirteenth century.  There are no Clement references after the 8th April 1347 although about twenty further documents cover the next fifty years with the last being dated 20 May1398.  Perhaps significantly, 1347 is on the eve of the appearance of the Black Death in Bristol & north Somerset.

In the vicinity of Temple Cloud the plague outbreak seems to have been most severe in the winter 1348-9 (Bates-Harbin, 1917).  For example the Manor Roll of Ston Easton records that 12 of the 16 tenants of the manor died in 1348 (Janes, 2003).  It would seem the Temple Cloud Clement family either succumbed during 1348-9 or, in the immediate aftermath of the plague they were stimulated to move.  Evidence for the severity of the contagion in the parish of Cameley is unfortunately lacking but there are circumstantial details that suggest mortality could have been high.  For instance, in the adjoining parish of Hinton Blewett the incumbent priest died and was replaced in December 1348, but this replacement died too and was replaced after a few weeks in February 1349 (Bates-Harbin, 1917; Holmes, 1896).  Also in February, the priest at High Littleton, who had been instituted in June 1348, died and was replaced (Bates-Harbin, 1917; Holmes, 1896).  As both Cameley village and Temple Cloud are located midway between Hinton Blewett and High Littleton it would seem probable that some residents of these settlements would have died about the same time the neighbouring parishes were so afflicted.   
 
On the other hand, in the 1433 Lay Subsidy, the total national tax yield, that had been fixed since the 1334 Lay Subsidy, was reduced by £4000. As a result each county was granted a remission of 10.4% of its tax quota, which was to be applied among ‘poor vills, cities and boroughs, desolate, wasted, destroyed, or very impoverished, or otherwise too heavily burdened with tax’ (Lee, 2002).   While in 1433 High Littleton & Hallatrow were given the highest reduction (38.14%) of any parish in the Hundreds of Chewton, Chew & Keynsham, presumably indicating that those villages were still desolate and wasted by the effects of the Black Death, Temple Cloud, Hinton Blewett and Cameley received no reduction on their pre-plague assessment (of 1334), implying perhaps that their economies and population had not suffered as greatly or had recovered.  

Figure 2: Historical population of England and I-Y33765 timeline in Chew Valley, Somerset (1000-2000). 

What is beyond doubt is that in 1348-9 the Black Death caused an uniquely large reduction in the population of England and that it took almost three centuries before that population had recovered to its pre plague level (see Figure 2). Between 1347, at Temple Cloud, and 1518, at Compton Dando, a period of 171 years, approximating to perhaps six or seven generations, we have no documented evidence for the Clement family in Chew Valley.  It seems to me this gap in the documentary record is most likely due to the economic and social adjustments that occurred throughout England during these “plague years” but I think it also strongly hints that several local Clement lineages probably became extinct at this time.  Evidence for the low frequency of the Clement surname in Somerset during this period is given by the index of Jurors in the Inquisitions Post Mortem Vols 18-26 (1399-1447) which contain only one Clement entry for the county, at Wincanton in 1427 (Ref E-CIPM 24-557).
 
So we can be sure that following the original wave of the Black Death in Somerset, and the repeated "ripples" of contagion during subsequent centuries, the size and distribution of the I-Y33765 Clement family in Chew Valley became significantly changed.  In Part 2 I will discuss some genetic and historical evidence for their relocation and expansion. 

 

 References

Bates-Harbin, E.H.(1917) The “Black Death” in Somersetshire, 1348-9,  Proceedings of the     Somerset Archaeological and Natural History Society, V63 pp 89-112

Dickinson, F.H.(1889) Kirby’s quest for Somerset. Nomina Villarum for Somerset of 16th of      Edward the 3rd. Exchequer Lay Subsidies 169/5, which is a tax roll for Somerset of the first year of Edward the 3rd. County rate of 1742. Hundreds and parishes etc. of Somerset as given in the census of 1841. Somerset Record Society, Vol 3. 360pp

Faith, J (2009), The Knights Templar in Somerset, The History Press, Stroud 115pp

Green, E. (1904) Certificate of musters in the county of Somerset, temp. Eliz., A.D. 1569.         Extracted, and with notes, by Emanuel Green.  Somerset Record Society, Vol 20,370pp.

Holmes, T.S, (1896) The Register of Ralph of Shrewsbury, Bishop of Bath & Wells                    1329-1363. Somerset Record Society, Vol 10. 877pp

 

Janes, R.(2003) Pensford, Publow and Woollard, A Topographical History, Biografix, 92pp.

Lee, J.S. (2002) Tracing regional and local changes in population and wealth during the later  middle ages using taxation records:Cambridgeshire 1334-1563.  Local Population Studies Vol 69, 32-50.

Leys, A.M (1941) The Sandford cartulary, Oxfordshire Record Society Vols 19 and 22

Mills, A.D.(2011) A Dictionary of British Place Names, Oxford University Press.

Reaney, P.H (1967), The Origin of English Surnames, Routledge & Kegan Paul, 415pp

I-Y33765 and nineteenth century emigration from Europe

The nineteenth century was a time of mass migration from Europe and we have evidence that some I-Y33765 men participated in these movements.  For example, we know that today, men with this Y-chromosome mutation are living in New Zealand and Australia and that these men are descended from one migrant, Shadrach Clement, a farmer from West Harptree, Chew Valley, England, who emigrated with his wife and family in 1857.  These pioneers sailed from London as steerage passengers on 11th June in the ship Glentanner and arrived at Lyttleton, Canterbury, New Zealand on the 3rd October, 1857 (see Figure 1).  Since then Shadrach's lineage has prospered in Australasia and today we can identify at least a dozen living I-Y33765 direct-line male descendants.  For example, Clement IN82043 is the 2x great-grandson of Shadrach. 

Figure 1:  Part of the report published on page 4 of the Lyttelton Times, Volume VIII, Issue 514, 7 October 1857, reporting the arrival of the Glentanner in New Zealand and containing the names of Shadrach Clement's family.  This "safe landfall" for Shadrach and his two sons likely marks the first arrival of the I-Y33765 marker to Australasia.

Shadrach Clement was a descendant of the English arm of the I-Y33765 clade but as I have discussed in earlier articles, based on the seven BigY results we have within the clade it seems very likely that the Y33765 mutation originated in Scandinavia circa 20AD possibly in what is now south-east Sweden.  All four Swedish men who are derived for the SNP have documented male-line ancestry from the north-east of the province of Småland. During the years 1850 to 1930 there was considerable migration of principally young Swedish men and women to North America.  This exodus has been estimated (Blanck, 2009) to have involved 1.3 million Swedes moving principally to the United States but also to Canada.  The Swedish province from which the second highest numbers emigrated was Småland with 4.6 emigrants per 1000 inhabitants leaving in each of the 80 years, 1850-1930 (Graves, 1991).  So,did any men derived for I-Y33765  travel to North America among these Småland emigrants?  That would certainly seem possible.

Its now over two decades since FamilyTreeDNA (FTDNA) started offering direct-to-consumer Y-DNA testing in the USA.  Since then hundreds of thousands of men worldwide have taken some sort of Y-DNA test with the majority of these being used by men who are resident in North America.  The first 111STR result for a I-Y33765 (+) man was completed in 2013 and a year later in an early BigY result (Clement 236748) the SNP was first identified although not named until it was recorded by YFull.com in analysis of the BAM file from a second BigY (Clement 282009) in 2017. The first positive Swedish results for I-Y33765 (Jacobsson IN70815 and Eklund IN78306) date from 2019 and early 2020 but at present no Y-DNA evidence has been found for I-Y33765 men in North America.  This is noteworthy because, of the eighteen clades downstream of Y4252 (Source: The I-Y4252 Draft Tree, 13 November 2020, I2a Project, FTDNA) all but I-Y33765 have already been recorded in tests of men who are today living in North America but who have known or unspecified European ancestry.

Just because I-Y33765 has not so far been recorded in North America doesn't mean we have no evidence for men with this mutation migrating there from Europe.  In 1850, at about the time the great period of Swedish migration was beginning, Henry Clement, a stone mason from Bristol England, is recorded in the US Federal Census working as a labourer in China Township, Wyoming County, New York.  Henry is a 3x great-uncle of Clement 236748 & 282009.  Henry had just married when he emigrated but his wife died soon after they left England. In 1855 he remarried in Kane County, Illinois and he and his new wife, herself an immigrant from Ireland, subsequently had two daughters.  Henry fought in the Union Army during the American Civil War and, after his capture at the Battle of Shiloh, died in a Confederate prison camp in September 1862 (see Figure 2). 

Figure 2: Henry Clement (1825-1862), grave marker at Andersonville National Cemetery, Georgia, USA.  Henry was a private in the 58th Illinois Volunteer Infantry during the American Civil War and died in the Confederate prison camp at Macon, Georgia, CSA.  His story is the earliest evidence we have for an I-Y33765 derived man in North America but his line "daughtered out" with his death.  Although he has no direct male descendants, the hand in the photograph resting on his grave marker belongs to one of his many great-grandsons in the USA, Clement Kinnicutt (1939-2017).  The photograph was taken in 2014.

In 1870, a few years after Henry Clement's death, one of his distant cousins from Chew Valley, North Somerset, Hugh Clement a coal miner of Bishop Sutton and a 1st cousin of Shadrach who was mentioned earlier, emigrated with his wife and young family to Knightsville, Clay County, Indiana, USA.  Hugh and his wife lived in Indiana for the rest of their lives and had two sons and a daughter.  Both sons married and each family had two daughters. So again, while Hugh, like Henry, has many descendants living today in the USA, his I-Y33765 Y-chromosome "daughtered out" and these two examples illustrate how male lines frequently end, especially when family size is reduced.

While it is relatively easy to follow the migration of I-Y33765 to North America with men in the English descendant arm, by using the association of the mutation in North Somerset with the Clement patrilineal surname, things become more complicated within the Swedish arm of the clade. This is because of the patronymic surnames which were most usually used in Sweden and other Nordic countries up to at least the end of the nineteenth century.   

In the patronymic system a last name is created by using the father’s first name and attaching a prefix or suffix that denotes the relationship of the child to the father.  Hence, when a chap named Lars had a son named Peter, the boy's full name was Peter Larsson and, the same man's daughter Hannah was known as Hannah Larsdotter.   Of course, when Peter Larsson in his turn had a son he named Lars, that young man was called Lars Petersson, and hence the greater complication for the genealogist becomes explicit.  

Fortunately, some non-patronymic surnames were also used in Sweden and among these the Eklund surname is associated with I-Y33765 and with the parish of Lofta in Tjust.  The Big Y-700 test for Eklund IN78306 shows that he is derived for Y33765 and downstream mutations and he appears to be the 3x great grandson of Lars Nilsson Eklund (1778-1825) who was a resident of Lofta parish. 

By using genealogical databases at Ancestry.com, Familysearch.com, Anarchiv.se and other internet resources I have recently traced two Ecklund lineages descended from the Lofta family of Lars Nilsson Eklund which have living direct-line male descendants in the United States.  Lars's eldest grandson, Lars Petter Eklund emigrated to North America with his wife and family in 1884.  During the 1880's emigration from Småland peaked at about 11 emigrants per 1000 of the population (Graves, 1991).  Two of Lars Petter's sons, Karl Gustaf Ferdinand (1869-1954) born in Lofta, and Daniel Oskar (1882-?) born in Dalhem, eventually had jobs in Chicago, Illinois. In 1910 Chicago had the largest Swedish population of any North American city with Swedish immigrants accounting for 11% of it's population (Sawyer, 1999).  Karl Eklund worked as a rail-car repairer and brother Daniel was a passenger elevator operator.  By the 1920's both were married with families and by then the spelling of their surname had changed slightly to Ecklund.  Today, both brothers have living direct male descendants in the United States among whom, Daniel's grandson and great-grandson are living in Los Angeles, California.  They are respectively 3rd cousin and 3rd cousin once removed to Eklund IN78306.  While, in the absence of a positive SNP test, we cannot assume these Californian Ecklund men are derived for Y33765, their documented ancestry certainly makes that look plausible.   I am sure that if, at some point in the future, we can confirm their supposed I-Y33765 (+) status, then that will help to provide a fuller understanding of the development and distribution of I-Y33765 in Sweden and beyond.

References

Blanck, D., (2009), Swedish Immigration to North America, Swenson Swedish Immigration Research Centre, Augustana College, Rock Island, Illinois, USA

Graves, P., (1991), Emigration and Literature: Vilhelm Moberg, Scottish Society for Northern Studies Vol 28, p35-40. 

Sawyer, K., (1999), The Emigrants from Småland, Sweden.  The American Dream, http://www.swedesintexas.com.

 

A new branch downstream of I-Y33767 defined by BZ4354

Recently, a Big Y-700 test has been completed for Clements B742594. This is the fifth set of next generation sequencing (NGS) results we now have for men on the English arm of the I-Y33765 clade; the previous tests are two Big Y-500 tests (Clement 236748 & 282009) and two Big Y-700 tests (Clement 236748 & IN82043).

Before the completion of the latest analysis, genetic testing has established that the English arm divides into several lineages downstream from I-Y33767, possibly at some time during the later decades of the sixteenth century.  Further, using the documented genealogies of the five men known to be derived (+) for Y33765 it seems probable this divergence happened between Clement/s male lines that were living in the valley of the River Chew, North Somerset. 

As I discussed in my June blog, a comparison of 111STR results for Clements B742594 and three Clement men (236748, 282009 & IN82043) gave a hint, based on repeat values at two markers DYS481 and DYS717, that he was more closely related to Clement 236748 & Clement 282009.  All three men share a 26 repeat motif at DYS481and they also have a 19 repeat motif at DYS717.  In contrast, Clement IN82043 has 25 repeats at DYS481 and 20 repeats at DYS717. So, using these STR comparisons, in the June update I speculated that downstream from I-Y33767 the English branch divided, with Clement 236748 & 282009 with Clements B742594 in one group and Clement IN82043 in the other.  As we will see my speculation was correct about there being a branch below I-Y33765 but entirely wrong about the way in which these four men are related.

This error became clear immediately we had the complete Clements B742594 Big Y-700 result.  This shows that Mr Clements is ancestral for three SNPs for which each of the Clement men (236748, 282009 & IN82043) are derived.  These mutations are BZ4354, FT314945 & FT324244 and we can now see that they divide the Chew Valley Clement/s into two distinct branches downstream of I-Y33767.  Hence, because of these definitive "next generation sequencing" (NGS) data from Mr Clements Big Y test we can reject my mistaken conclusions based on STR comparisons and instead be confident of this division defined by the BZ4354 SNP.  This relationship is illustrated in our new I-Y33765 chart shown below.

Rather than removing the previous blog (June, 2021) that contains my incorrect assessment based on the STR comparisons, it seems to me that, together with this update, it illustrates the pitfalls of relying solely on STR markers and once more demonstrates that only SNP mutations provide a "gold standard" genetic assay for genealogy. 

Click on image to enlarge

I-Y33765 draft tree showing Short Tandem Repeat (STR) marker mutations, June 18th 2021

Previously, the charts I have drawn to illustrate our developing understanding of phylogeny for the I-Y33765 clade have been based on Single Nucleotide Polymorphism (SNPs) results from FTDNA Big Y-700 next generation testing.  In this draft however I have sketched a tree which shows  the estimated positions of Short Tandem Repeat (STR) marker mutations downstream from Y33765.  My interpretation is based on comparison of the results of eight men who have each tested 111 STR markers at FTDNA.  

Those mutations shown in blue type on the chart are "back" mutations in which the number of repeat motifs at that marker has been reduced compared to the upstream value shown in black, while "forward" mutations, in which the number of repeat motifs has increased, are shown with red characters.  The chart demonstrates how STR markers mutate randomly over time with both "forward" and "back" mutations happening at an apparently similar frequency on each of the lineages within our clade.

Most of the observed mutations are, as might be expected, in the fastest mutating STR markers but four of these changes have occurred in markers with the slowest rate of mutation.  All these slow marker mutations have occurred at some point during the last ten to fifteen generations, so within the conventional genealogical time-frame.  One of the English lineages, Clement IN82043, at marker DYS717 shows an increase from 19 to 20 repeats.  On the Swedish arm of the clade, Eklund IN78306 has a "forward" mutation from 18 to 19 repeats at DYS587 and a "back" mutation from 14 to 13 repeats at DYS497.  Lastly the Swedish, Jacobsson IN70815 lineage has a "back" mutation from 12 to 11 repeats at marker DY568.  Again, we can interpret these changes as demonstrating the completely random nature of alterations in Y-chromosome STRs. 

The most significant relational change in this latest version of the I-Y33765 tree concerns the expansion of the English branch downstream from I-Y33767.  Comparison of the 111STR results for Clements B742594 (in previous iterations of the I-Y33765 tree shown as YS32054) with those for the other English men has shown that he is most closely related to Clement 236748 and Clement 282009.  This finding prompted a reconsideration of the known documented genealogies for these three men and, as a result of this, a putative connection has been found between them with their most recent common ancestor (MRCA), George Clement, who was baptized at St Mary the Virgin, Compton Dando, Somerset, 1st December, 1678.  This finding would seem to indicate that the genealogies of all the presently known instances of I-Y33765 in England can now be shown to originate from an area of north-east Somerset close to the parish of Clutton.  Previously the earliest known Clement ancestry for 236748 and 282009 was in south Gloucestershire.  

Regular readers will recall that I have several times discussed my feeling that a plausible explanation for the localization of an originally Scandinavian I-Y33765 male lineage in north Somerset can be proposed by linking its patriarch to north Somerset manors that, like Clutton, were owned by men of Scandinavian descent during the two generations that preceded the Norman Conquest.  It seems to me this latest redefinition of genetic relationships on the English arm of I-Y33765 supports this hypothesis.  If you are interested in more discussion on this theme then I suggest you may want to look at these earlier blogs published 24 September 2020, 21 & 23 October 2020 and 11 April, 2021.    

Click on image to enlarge

In the above post, my conclusions about the genetic relationships between the five English Clement men, that I had based on a comparison of their Short Tandem Repeat (STR) 111 marker test results are incorrect.  Consequently, in the above chart the arrangement of branches downstream of Y33767 is wrong and should be ignored.  My mistake has been confirmed by the "next generation sequencing" results from the BigY-700 analysis completed for Clements B742594 in July 2021 (for a full update please see my blog published 8 August 2021). 

It seems to me that it is probably helpful to leave this incorrect post on-line because it illustrates the folly of relying solely on STR markers and nicely demonstrates that only Single Nucleotide Polymorphism (SNP) mutations can be considered a "gold standard" marker for genetic genealogy.

JAC, 8th August, 2021 

The I-Y33765 clade and Chew Valley, Somerset, England -- Part 2. Y-DNA haplogroup frequencies, surnames and descent clusters

In two previous articles (see October 2020) I have explored the association between the I-Y33765 clade and the Cult of St Clement.  It seems to me that this connection is noteworthy because the Clement hereditary surname which is shared by English men who are derived for the I-Y33765 mutation is generally considered to originate from the name of this early Christian martyr. During the initial phase of conversion of pagan Viking Scandinavia to Christianity the Cult of St Clement became associated with the ruling elites of Norway, Denmark and England.  Clement had been Pope during the first century, and was subsequently martyred by being thrown into the Black Sea tied to a ships anchor.  This method of martyrdom appears to have made him a fitting patron for Viking societies whose existence depended on seafaring, maritime trade and naval prowess. 

In England, as inherited surnames became adopted after the Norman Conquest, some followers of St Clement's cult seem to have adopted his name as their family name and so by the thirteenth century it is found as a patrilineal surname in several English counties.  The dispersed nature of these early recorded instances of the name in England may perhaps suggest its adoption happened separately in different localities and so, as a surname, it became associated with unrelated Y-chromosome lineages. 

The Y-chromosome and patrilineal surnames are inherited in a similar way and hence demonstrate an explicit correlation. In other words, Y-DNA and surnames can be used to demonstrate co-ancestry. In an early review of this correlation (King & Jobling,2009) populations of men with more common surnames showed greater Y-haplogroup diversity implying that common surnames in England were founded many times and hence contained lineages derived from many patriarchs.  So, for the commonest English surname, Smith (652,500 holders), the Y-haplogroup diversity was very similar to that of the general population (see Figure 1a) whereas rare surnames, such as Attenborough (1,065 holders) were associated with a single haplogroup and may have had a single founder.  

In England, these less common surnames that demonstrate clear evidence of co-ancestry have less than 5,600 holders (King & Jobling,2009).  The Clement surname and its close spelling variants (Clements, Clemens, Clemons) is significantly more frequent than this co-ancestry threshold figure (in 2002 Clement variants had 24,200 holders in England, Wales and the Isle of Man) and consequently it has a Y-haplogroup diversity which is very similar to that found in the English male population (see Figure 1b). 

Figure 1: Y-DNA haplogroup frequencies (a) in England (Source, Eupedia, May 2021) (b) in the Clements Surname DNA Project, n = 257 (Source, FTDNA, May 2021).  This comparison shows that holders of the Clement surname represent a Y-DNA haplogroup diversity that is similar to that found in the English male population and this suggests that the name had a large number of founders. Numbers are % figures.  (Note: the majority of members of the Clement Surname DNA Project at FTDNA indicate their paternal origin as being from the USA and hence the data illustrated here should be considered to represent an English speaking North American Clement population.)

From Figure 1(b) we can estimate that one in four men with the Clement surname in England and the USA are likely to have an I haplogroup Y-chromosome and one in five will probably be haplogroup I2a.  As we know, in England, the Clement/s descent cluster originating from the Chew Valley, Somerset, is part of the I-Y33765 clade which itself is a small descendant branch of the I2a haplogroup (see Table 1).

 

Table 1: The I2a haplogroup.  The table shows the descendant haplogroups within I2a leading to I-Y33765. Age estimates are calculated using the method used by Adamov et al.,(2015)

At FTDNA (May 2021) the I2a Haplogroup Project has 3917 members who are each derived for the I-P37 mutation which defines the I2a haplogroup.  Within this sample of I2a men, 303 (approximately 8%) have tested positive for the much more recent Y4252 mutation which is immediately upstream from Y33765 (see Table 1).  Using this information, we can calculate (100 / 8) * 5, and so suggest that fewer than one in sixty men with the Clement surname are likely to have an I-Y4252 haplogroup.  

Now at this stage it seems to me only proper to make it absolutely clear that the method I am using to make this guesstimate is very "rough and ready".  Even so, it does I think allow me to illustrate how the molecular genetics of the Y chromosome can lead us to identify a small population as a descent cluster even in a genetically diverse group like English men with the relatively common Clement/s family name.  As mentioned earlier, in 2002 in England there were 24,200 holders, both men and women, with Clement variant names.  So we can suppose that about 12,100 / 60 men in England may have an I-Y4252 Y chromosome; so perhaps we are considering just 200 or so men.  Given the much larger threshold below which descent clusters have been shown in groups of men sharing an unusual surname (<5,600 holders) it would seem reasonable to assume the I-Y4252 Clement men in England will probably represent descent from a single founder.

From the evidence we have at present all the I-Y4252 Clement/s men with English ancestry are also derived for the downstream Y33765 mutation and have co-ancestry from the Chew Valley, Somerset.  It seems to me this strongly suggests a single founder for the I-Y33765 Clement/s descent cluster and that he probably lived in what is now NE Somerset.  Since we know that the Y33765 mutation formed in Scandinavia during the Iron Age it seems logical to look for reasons why a Scandinavian man might be fathering sons in NE Somerset towards the end of the first milenium.  Not surprisingly this brings us back to the several manors in north Somerset that are mentioned as being owned by "the Dane" in the Domesday Book (Lewis, 2016), and in particular to the manor in the Chew Valley owned by Thorkil "the Dane" at Clutton.

References    

Adamov, D., Guryanov, V., Karzhavin, S., Tagankin, V., Urasin, V. (2015) Defining a new rate constant for Y-chromosome SNPs based on full sequencing data. Russian Journal of Genetic Genealogy 1:3–36

King, T.E.,Jobling, M.A.(2009) What's in a name? Y chromosomes, surnames and the genetic genealogy revolution.  Trends in Genetics 25, 351-360

Lewis, C.P. (2016) Danish Landowners in Wessex in 1066, in Danes in Wessex, Eds Ryan Lavelle & Simon Roffey, Oxbow Books, p 172-211