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June 27, 2019

This article will look at two aspects of Y-DNA matching, the concept of Genetic Distance and the possibility of examining individual marker (STR) mutations to inform family relationships. Examples will be provided from Family Group F to help flesh out these concepts, but you can easily apply these methods to your own family groups.

When you look at your Y-DNA matches, have you wondered what Genetic Distance (GD) really means and how seriously you should take the results? GD is the first column on your Y-DNA Matches page with numbers between 0 and 10 for men who have taken the 111-marker test, 0 to 7 for the 67-marker test, 0 to 4 for the 37-marker test, etc. “0” means you have no marker differences with that individual, “1” means one marker difference, etc. Along with this explanation of how to compute GD, we’ll also look at a real world example to see how you can dive deeper into marker differences to see what else these results might mean for your ancestor search. Of course, “markers” is just another name for STRs (Short Tandem Repeats). For more information about STRs, go to the FTDNA Learning Center or other sites like or

The graphic below shows Y-DNA results for all the Pruitts, Sweeneys and Whites who make up Family Group F. The Sweeneys and Whites are members of other surname projects, but we all recognize that we are descended from the same ancestor who lived around 300-400 years ago. The graphic has been simplified and does not contain the 91 markers that are identical for the 8 testers who took the 111-marker test or the lesser number of markers for those who took 67 and 37 marker tests. The cells with a yellow background indicate those markers that are different from the majority of men who tested for that marker. To see a larger version of the chart below, left click on it. To see the chart in another tab or window, right click on it and select "Open link in new tab" or "Open link in new window."

What do marker (STR) differences (or GD) tell us about the relationship of the Sweeneys, Pruitts and Whites? Let’s look at two examples to see how good GD estimates can be and the peril of taking it too seriously in some cases. Comparing Pruitt 3 who descended from Asa Pruitt to Pruitt 4 who descended from Bird Pruitt, you will see that there are four marker differences, so a GD of 4. [Remember, all markers not shown are identical.] GD 4 is actually a very good estimate since the most recent common ancestor of these two testers was Thomas S. Pruitt, the father of Bird and Asa, who was born 4 generations before our testers. Now, let’s look at a couple of the Whites, the descendants of Littleberry and Cajabeth. There are three marker differences between the descendants of these two men, thus a GD of 3. The most recent common ancestor of these two testers was Moses Swinney, the father of Littleberry and Cajabeth who was born 8 generations before our testers. In this case, GD gives us a very poor estimate of the relationship of the descendants of these two men. Why? For whatever reason, the Whites have had far fewer STR mutations in the last 200+ years than the Pruitts. If you examine the markers that are different than the norm (yellow background markers), then the Pruitts have had 9 markers that have mutated from the norm in one or more descendants and the Whites have had 4 markers that have mutated, a more than 2-1 ratio. If you throw out the identically mutated markers, like DYS452, then the ratio is 7-4, still nearly 2-1. Given the lack of mutations in the Whites, their descendants are going to appear to be closer than they actually are.

Can we learn anything by looking at the specific marker mutations? Perhaps. Let’s look at three instances that jump out at first glance.

1. The mutations at DYS389i, a relatively slow mutating marker, may suggest a point where Sweeneys 2, 3 and 5 split from Sweeneys 1 and 4, before the Pruitts and Whites split from the Sweeneys. That would mean that the Pruitts and Whites descend more directly from the Sweeney line with a value of 14 for that marker. The other possibility, of course, is that these were random mutations that occurred later. Without more testing and some historical records to confirm this hypothesis, we really can’t know for sure.

2. The consistency of the mutations at DYS464a and DYS452 may suggest a point where the Pruitts split from the Sweeneys, before some of the Pruitts split from each other in the early 1700s. Given this, another marker, DYS537, a slow mutating marker, may offer an opportunity to predict a result before it is known. We know that Pruitts 1 and 2 are descended from one son of Samuel Pruitt, b. ~1700, and Pruitts 3 and 4 are descended from another son. If that marker mutated after the split, then it could be predicted that Pruitt2’s value would come back as "10" if he were to upgrade to 67 or 111 markers.

3. The Whites are a special case because they have so few mutations. In fact, their markers may represent our best guess as to the actual Sweeney markers going back in time. In other words, their markers may be more Sweeney-like than the descendants who carry the name Sweeney or Swinney. Even with the Whites, however, the mutations at DYF395S1a, a very slow mutating marker, may suggest a point where the Whites split from each other. We wouldn't be surprised if White 1 is a descendant of Littleberry Sweeney White and White 4 is a descendant of Cajabeth White. [Littleberry and Cajabeth are two documented sons of Moses Swinney of Granville, N.C.] One way we might determine if this is true, besides finding historical records to confirm it, would be if the other three Whites were to upgrade to the Big Y like White 1 has done and if their Terminal SNPs were to line up according to this prediction; i.e., Whites 1 and 2 were to have a shared Terminal SNP and Whites 3 and 4 were to have a different shared Terminal SNP.

This last example offers a good segue to the next article where we’ll look at how STRs and SNPs can be used together to piece together your family tree when historical records are lacking. For more on SNPs (Single Nucleotide Polymorphism), see the above sources and the two articles below.

May 25, 2019

Thanks to a site called SNP Tracker, there's another way to look at our Big Y-700 results. The image below shows the path that ancestors of Family Group F Pruitts took to the British Isles. [You can click on the image to open a larger version in your browser.] Our previous Haplogroup R chart started with Haplogroup R-M207 (i.e., SNP M207) which formed around 31,000 years before the present (YBP). The map below starts with Haplogroup A-PR2921 which formed around 240,000 years ago in west Africa. Think of this Haplogroup as the starting point for modern humans. You can track the migration of these early humans across Africa to the point where they crossed over to the Arabian Peninsula around 70,000 YBP. After years migrating through central and western Asia, these ancestors to our Group F Pruitts (and most western Europeans) would have crossed into Europe around 13,000 YBP. Around 6,000 YBP they would have started their slow march to western Europe and ultimately to the British Isles where we find the Group F Pruitt Haplogroup R-FT23457.

This second map provides a little more detail for the western European portion of the migration.

Try putting your terminal SNP in the Search window of the SNP Tracker. Your track will be similar, except that Family Groups D and E will take a more direct route to Europe and, since no one has taken the Big Y, will end thousands of years earlier than this Group F example. An interesting feature of SNP Tracker is that it shows the number of descendants in the FTDNA database who are positive for a particular SNP. When you click on the SNPs tab, you'll see a list of your SNPs in chronological order and further to the right you'll see how many people tested positive for that SNP (Number of Descendants column). Of course, the numbers drop with each new SNP until you see the last SNP has just a few, but no less that 2 since that's what it takes to define a new SNP. This demonstrates the power of the Big Y and the limitations. To really refine your location on the Haplogroup tree, you must find cousins who are willing to take the test. In the case of Group F Pruitts (including "closely" related Sweeneys, Whites and others), we have found eight direct line males who have been willing to take the Big Y test. That's why our Haplogroups (FT23457 and FT55898) have brought us so close to the present. In our case, we are trying to sort out our Sweeney-Pruitt relationship, and the Big Y is giving us some answers. More on that in a future installment.

May 9, 2019

With the increasing number of Big Y tests being taken by our members, it seems like an appropriate time to dive into the early results to see what they’re telling us. We’d like to answer some questions like: What is the value of Big Y testing? What are the results telling us about our relationships to other Prew-its and to our matches with other surnames? What other things could it tell us in the future? Will it help if more people take the Big Y test?

As a result of the Big Y, we can now provide a SNP (pronounced "snip") view of our family relationships (see the chart below - click on the chart to open up a larger version in your browser). [We could also call this a Haplogroup view; just put “R-“ in front of a SNP name and you have the name of the Haplogroup.] In the past our understandings of family relationships have come from STR testing through tests like the Y-DNA 111. STRs mutate more quickly than SNPs. For that reason and others, STRs are pretty useful in identifying relationships within the last 300 years or so. Based on this STR view of our family relationships, we've known for some time that our six Prew-it family groups likely are not related within the time period since the late Middle Ages when surnames became customary in Western countries. As shown in the chart below, Big Y test results have confirmed this. Each light blue block is a SNP or Haplogroup shared by one or more Prew-it family groups. Up until around 4,800 years ago, all of our Prew-its were in the line from M207 to P312 (along with most Western Europeans). At that point, the individuals whose descendants would later make up Family Groups A and B split off from Family Groups C and F. Family Groups A and B continued on a line to Z39589 where they split around 4,000 years ago. By contrast, Family Groups C and F continued on a line from P312 to U152 where they split around 4,500 years ago.

So, we quite clearly had four family groups of future Prew-its long before they actually took on the Prew-it surname. [Unfortunately, no members of Family Groups D and E have taken the Big Y, so we can’t include them on our chart.] How did it happen that several unrelated families independently took on the Prew-it name? With more Big Y tests, we may get some answers. Two particularly interesting Family Groups are A and F. With Family Group A, we have a number of people with Morris and Greene surnames who may be related to Pruitts within the last 300-400 years (based on STR testing). We have a similar situation in Family Group F with Pruitts and Sweeneys. In the latter case, we have reason to believe that the Pruitts are really Sweeneys and the causal effect was a non-paternity event. We’re fairly confident that more Big Y tests will give us clues to when this separation occurred. We’ll try to provide more details about this split and how Big Y testing could help solve the paternity issue in a future article.

November 18, 2018

To accompany the tax list article below, here is a map of Virginia from the 1790s with relevant counties in bold.

November 16, 2018

Below are tax lists for years on or about 1790 and 1800 showing the names of Prew-its who paid personal and land taxes in the counties of Virginia. Because the Federal census records for Virginia for these years were burned by the British in 1814, this is a helpful substitute. This material was developed from Binns Genealogy website (

Tax Lists for Virginia Counties (P - Personal Tax, L - Land Tax)


County Taxpayer Name
Taxpayer Name 

(Year/Type of Tax Paid)
(Year/Type of Tax Paid)

Accomack George Prewitt (1789 P)
George Prewitt (1799 P)

William Prewitt (1788 P)
Benjamin Prewitt (1799 P)

John Prewit (1799 P)

Campbell Bird Prewitt (1791 P)
Michael Prewit (1800 P)

Robert Prewitt (1791 P)

Caroline William Pruett (1789 L)
Moses Pruet (1799 P)

Thadeus Pruet (1799 P)

Charlotte Joseph Prewett (1790 P)
Joseph Prewett (1800 P)

Franklin David Prewit (1788 P)
Elisha Prewett (1799 P)

Eligah Prewit (1788 P)
Jane Prewett (1799 P)

John Prewit (1788 P)
John Prewett (1799 P)

Henry Michajah (1790 P)

Goochland Abraham Prewit (1789 P)

Allan Prewit (1789 P)

Hayward Prewit (1789 P)

Obediah Prewit (1789 P)

Halifax Allexander Prewit (1789 P)
Thomas Prewitt (1798 P)

Michael Prewit (1789 P)

William Pruett (1789 P)


Edmond Prewet (1801 P)

James City Benjamin Prewit (1790 P)
Benjamin Prewitt (1800 P)

Benjamin Prewit (1790 L)
Benjamin Prewitt (1800 L)

Benjamin Prewit (1790 L)

James Prewit (1790 P)

Mary Prewit (1790 L)

King and Queen Francis Prewitt (1790 L)
Dunstan Prewitt (1799 P)

Francis Prewitt (1790 P)
Frances Prewitt (1798 L)

James Prewitt (1790 P)
Franky Prewitt (1799 P)

Reuben Prewitt (1790 P)
Richard Prewitt (1798 L)

Richard Prewitt (1799 P)

Pittsylvania Archibald Prewet (1789 P)
Elijah Prewitt (1800 P)

John Pruett, Jr. (1789 P)
Japhitte Prewitt (1800 P)

John Pruett, Sr. (1789 P)
John Prewett (1800 P)

Joseph Pruett (1789 P)
John Prewett, Sr. (1800 P)

Joseph (Bannister) Pruett (1789 P)
Joseph Prewett (1800 P)

Joshua Pruett (1789 P)
Joshua Prewett (1800 P)

Richard Prewit (1789 P)
Mary Prewitt (1800 P)

Samuel Pruett (1789 P)
Samuel Prewitt (1800 P)

Samuel Pruett, Jr. (1789 P)
William Prewett (1800 P)

William Pruett (1789 P)
Zachariah Prewitt (1800 P)

Zachariah Pruett (1789 P)

Wythe John Pruett (1793 P)
John Pruet (1800 P)