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Time to Most Recent Common Ancestor Shifts Way Back

In June, 2022 Family Tree DNA’s modelling indicated that the time to the most recent common ancestor (TMRCA) shared by all Y-DNA test-takers in our SAINSBURY-SANSBURY family was about three to four hundred years ago, or around the year 1675.

The above diagram shows Family Tree DNA’s June 2022 estimate for the time to our most recent common ancestor. The year 1675 was the mean, with a 95% confidence interval that our MRCA lived as early as 1497 and as recently as 1803.

That time estimate worked well with our leading theory (see, for example, Y-DNA proves Urchfont origins of north Somerset Sainsburys) which put forward John Sainsbury the younger of Urchfont, Wiltshire as the most recent common ancestor (MRCA) of the following families:

  • Daniel SANSBURY of Cheraws District, South Carolina (c.1750?-1816); green columns on the left in the diagram below,
  • two SAINSBURYs with documented roots in Wiltshire; blue columns in the middle, and
  • our north Somerset ancestor, Richard SAINSBURY (1708?-1785); orange column on the right

But Then Two Things Happened

In the fall of 2022, however, two things happened to upset this theory, which until then had been working out quite nicely.

In September 2022, Family Tree DNA revised the model it uses to estimate TMRCAs. (See their blog post: Scientific Details: A Deeper Dive Into Age Estimates.) This set our genetic clock back by about 200 years, making it much more difficult (but still not impossible) to reconcile with our leading theory. (That John SAINSBURY the younger, born 1664, is our most recent common ancestor.)

Then, in October, 2022, we received a new Y-DNA test from a SAINSBURY in the UK whose family line, at first, seemed corroborative of our leading theory. But, on second glance, may actually make that theory more unlikely. (See: Big Y-700 results corroborate John Sainsbury (1664-1719) as ancestor of north Somerset Sainsburys?)

What Do the Experts Say?

According to a Big Y Specialist at Family Tree DNA:

It looks like the new TMRCA estimate for all SAINSBURY and SANSBURY descendants at or downstream of R-FTA27580 (see The R-FTA27580 Story) is now the year 1446 on average. Whereas, for two descendants now grouped together on the Big Y Block Tree (those in the light blue R-FTD18964 column in the above diagram), their TMRCA is now estimated to be 1470 on average, give or take a couple of centuries. (See The R-FTD18964 Story.) This pushes the average back, but a MRCA born around 1664 and siring children around 1700 is still within the potential spread.

Adapted and used with permission; my emphasis

The diagram below shows the latest TMRCA estimate for our SAINSBURY-SANSBURY family. The year 1446—not 1675—is now the mean.

A 95% confidence interval no longer includes the time during which John SAINSBURY the younger (1664-1719) was alive and having children. Therefore, the likelihood that he is our most recent common ancestor seems much diminished since the June, 2022 modelling indicated a MRCA alive in or around the year 1675:

Single Tandem Repeat (STR) Analysis

Family Tree DNA’s Big Y Specialist also noted that the two Wiltshire-originating SAINSBURYs in haplogroup R-FTD18964 match at Y-111 with a genetic distance (GD) of eight STR marker mismatches.

According to the new Y-STR marker TMRCA chart, the TMRCA for those two SAINSBURYs, who match at Y-111 with a GD of eight, should be an estimated 590 years before present on average, give or take a few hundred years. In other words they have a MRCA who was born around the year 1432 on average, with a 95% confidence that their MRCA was born between the years 1082 and 1702.

In summary, odds are that the TMRCA between the two SAINSBURYs who constitute haplogroup R-FTD18964 was in the mid-1400s but it is within the realm of plausibility that they could have had more mutations than average within that timeframe and had a MRCA born around 1660 or 1700

Adapted and used with permission; my emphasis.

Testing the Realm of Plausibility

Whether or not our SAINSBURY lines have had more-than-average mutations in our Y chromosome (and we can therefore feel confident that our TMRCA is closer to 1675 than 1470) can be tested a couple of ways:

  • One, if we can find distant but documented cousins to test, their test results could help calibrate our family’s “Y-DNA clock.” Those additional tests may indicate whether the Y chromosome in any or all of our family lines shows an above-average rate of mutation.
    • To this end, we’re expecting results from a Y-37 test by the end of March, 2023 from a SAINSBURY in the UK who belongs to the “R-FTD18964” branch of Wiltshire-originating SAINSBURYs;
    • We’re also hoping to contact an Australian SAINSBURY who is distantly related to the only test-taker we currently have from our north Somerset family. A second Y-DNA test in that line would conform to the methodology proposed by Pomery (2010) and establish a Y-chromosome mutation rate for our line.
  • Second, we are expecting the results of a Y-37 test in January, 2023 that could corroborate or refute the theory that (a) we descend from John SAINSBURY the younger (1664-1719) and (b) John SAINSBURY the younger was the biological son of John RUDDLE (1633-?). See SAINSBURY-RUDDLE triangulation group established.

The discoveries we make in 2023 may solve The Mystery of John Sainsbury the younger—and whether he or some other Wiltshire SAINSBURY was our SAINSBURY-SANSBURY family’s most recent common ancestor.

Join the Sainsbury-Sansbury Group

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.