Big Y-700 results corroborate John Sainsbury (1664-1719) as ancestor of north Somerset Sainsburys?

The Sainsbury-Family Group project on Family Tree DNA has received the results of a Big Y-700 test for a male SAINSBURY living in the UK. From earlier levels of testing (Y-37 and Y-111) we knew he was related to our north Somerset SAINSBURY family; these Big Y-700 results indicate the specifics of that relationship and help us understand our own origins.

Family Tree DNA’s Block Tree now shows three distinct SAINSBURY/SANSBURY family lines and has separated them into three Y-DNA haplogroups:

  • R-FTA75903: two SANSBURY cousins who descend from Daniel SANSBURY (c.1750-1816); if this were a typical family tree, Daniel SANSBURY would sit at the “5” mark on the ruler of variants (single nucleotide polymorphisms or SNPs) on the left side of the Block Tree (below)
  • R-FTD18964: two SAINSBURY cousins who descend from a common SAINSBURY ancestor who lived about one generation before Daniel SANSBURY (he would be placed at the invisible “6” mark on the chart below).
  • R-FTA27580: a descendant of the north Somerset SAINSBURYs who shares an ancestor with the others about one more generation back in time (i.e., at the invisible “7” mark on the numeric chart below).
Based on generational proximity, Family Tree DNA’s Block Tree has has grouped two US SANSBURY cousins in the first column, two SAINSBURY cousins in the middle column, and a third more distant SAINSBURY cousin in the third column. That column represents the SAINSBURYs of north Somerset.

If I’m understanding this correctly, the Block Tree representation of these five SAINSBURY/SANSBURY men who have tested at the Big Y level mirrors what we believe to be their genealogical tree:

Speculative family tree of these Big Y-700 matches based on available records. Known or suspected MRCAs are bold; suspected or unknown individuals are italicised.

This new data seems to corroborate what we suspected from the written records: that the MRCA shared by the two SAINSBURY cousins in the middle column was likely an uncle of Daniel SANSBURY (MRCA of the “South Carolina-originating” SANSBURYs) and a brother of the north Somerset SAINSBURYs’ earliest known/suspected ancestor, Richard SAINSBURY, who we believe (based on other genetic and documentary evidence) was born in Urchfont, Wiltshire in 1708 and died in Nailsea, Somerset in 1785.

Applying a Y-DNA mutation rate

Conventional Y-DNA analysis suggests Big Y-DNA mutations occur on average about once every 83 years. (See: Testing Benchmarks FTDNA Big Y-700.) Applying that formula to determine the approximate lifetime of the MRCA for everyone in this group gets us back to about the year 1420 (i.e., 7 variants on the Block Tree rules times 83 years per variant). But this seems very far out of line with what documentary and other genetic evidence indicates.

For another SAINSBURY haplogroup in the Sainsbury-Family Group project, using the 83-year average places their most recent common ancestor back in the 1200s. (See haplogroup I-FTA55120 in Family Tree DNA’s Discover tool.) But we’re very confident their MRCA lived in the late 1400s/early 1500s. So there’s a sense the average rate of change may be longer than appropriate in our SAINSBURY-SANSBURY calculations to determine the time back to any given MRCA.

However, thanks to the US SANSBURYs in this Block Tree, we know their MRCA, Daniel SANSBURY (c.1750-1816), had his children in the late 1700s, so we also know their Y-DNA changed at the rate of about 5 mutations in 250 years (to judge by the “5” in the chart on the left), or an average of about 1 mutation per 50 years. In the time since then, the Y-DNA of these two cousins developed an average of two private variants. (Actually, one cousin has one private variant, the other has two.) The 83-year average times two private variants gets us back about 163 years since these cousins were born: that is, the late 1700s, as we would expect. So the average number of years per mutation works . . . in this case.

However, while the ruler on the left indicates that the MRCA of the two SAINSBURY cousins in the middle column lived just a bit farther back in time than Daniel SANSBURY (c.1750-1816), —only enough time for their Y-DNA to develop one additional variant (which we can determine by reading across to the 6th position in the numeric chart on the left). their private variants tell a different story.

They are separated in genetic proximity by an average of 6 7 private variants. And (7 x 83) = 581 years, or about the year 1400. In other words, their MRCA would have to have lived at that time to allow enough time for those six seven mutations to develop in his present-day descendants.

By applying the “SANSBURY” rate of change, that one mutation represents a SAINSBURY man who lived about 50 years earlier than Daniel SANSBURY. In other words, only one or two generations before the late 1700s. So perhaps around the year 1700. This accords with our speculative family tree, which theoretically identifies their MRCA as Francis SAINSBURY, born in Urchfont in 1706.

The third column, without any nearer cousins, represents the north Somerset SAINSBURYs. Tracing up the Block Tree to the time of the MRCA we share with the other two family branches gets us back one more step to the “7” line. (Or Is this reading an incorrect application of the Block Tree’s ruler?) Using the same “50 years per mutation” average “83 years per mutation” rate derived from the SANSBURY data gets us back to about the year 1400. the mid-1600s. This accords with does not support our leading theory that all the men in this chart descend from John SAINSBURY the younger who lived from 1664 to 1719.

So do we belong to a different family group? Not the Urchfont Sainsburys as so much other evidence seems to suggest?

Next Steps

The genetic evidence presented here indicates that Joseph SAINSBURY (c.1787-1816), ancestor of our latest Big Y-700 test-taker, may descend from Francis SAINSBURY (b.1706 Urchfont). But only if his family line’s Y-DNA developed seven private variant mutations in as many generations.

However, many family trees on, based on available parish records, identify this Joseph SAINSBURY as the grandson of James SAINSBURY (b. 1715 Great Cheverell) who married Hester BLAKE in 1736 and subsequently lived in the hamlet of Littleton Panell in the parish of West Lavington, Wiltshire.

Are you a direct male descendant of William SAINSBURY and Hester BLAKE? Have you considered Y-DNA testing to learn more about your SAINSBURY origins?

Join the Sainsbury-Sansbury Group project on Family Tree DNA to learn more about Y-DNA and your family history! The results of your test will benefit your family history research and the research of many others with an interest in SAINSBURY, SANSBURY and variant surname lines.

Disclaimer: As with any research project, when new evidence comes to light, former theories may change. This blog post includes theories and conclusions developed from the best available evidence at the time this post was written. It may be corroborated or refuted by later research. This post must therefore be considered in the context of all information presented in earlier and later posts.

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