The Sweet-Swett-Sweat DNA project now has eleven participants named SWETT. Their lineages are in Table 1. Their test results are in Table 2 and Table 3. Further information is at the bottom of this page.

These are y-chromosome DNA tests, so they only address biological descent in the male line. They measure the lengths of specified markers on the y-chromosome. The measured results are interpreted statistically to show with a stated probability whether any two or more participants have a common male ancestor, and if so, the number of generations back to their most recent common male ancestor.

Trevor, Steven, Gary, David and Robert have an exact 25/25 match. Ben, Keith, Francisco, Charles, Raymond and Keith J. match them exactly on 24 of 25 markers -- and they each have a different one-step mismatch. This means it is very likely that the first five men have the DNA profile (haplotype) of John Swett of Newbury himself, and it is very likely that the other six men would match John Swett of Newbury exactly on 24 of 25 markers with 1 one-step mismatch.

24 exact matches with 1 one-step mismatch means:
99.9% probability the participants have a common male ancestor
90% probability their most recent common male ancestor is 20 generations or less (500 years or less)
95% confidence interval their most recent common male ancestor is 1-28 generations (more than 25 years and less than 700 years)

The participants' lines of descent from John Swett of Newbury (Table 1) show the following generations and years:
Trevor = 10th generation, 335 years
Steven = 11th generation, 344 years
Gary = 11th generation, 346 years
David = 11th generation, 358 years
Robert = 12th generation, 338 years
Ben = 10th generation, 344 years
Keith = 11th generation, 360 years
Francisco = 12th generation, 357 years
Charles = 12th generation, 359 years
Raymond = 11th generation, 356 years
Keith J = 12th generation, 370 years

Taken together, their genealogy and DNA test results prove beyond reasonable doubt that these eleven men and their direct lines of male Swett ancestors are descendants of John Swett of Newbury.

Further, these results provide a DNA profile (haplotype) by which other men who choose to participate in any DNA test that uses the same markers can prove with a high degree of confidence whether they are or are not related to John Swett of Newbury.

A major finding of the Sweet-Swett-Sweat DNA project is that participating descendants of John SWETT of Newbury and participating descendants of John SWEET of Salem (settled in Rhode Island and Connecticut) do NOT have a common male ancestor in the last 3,000 years. Although SWETT has often been described as a variant of SWEET, these DNA test results prove they are two separate families.

The Sweet-Swett-Sweat DNA project website explains the rationale and plan of action. http://www.fairleafarm.us/dnasweet.htm

Anyone interested in participating should email John Chandler <john.chandler@alum.mit.edu> and put "Sweet-Swett-Sweat DNA" in the subject line. You can ask him questions and/or ask him to sign you up for the project. He can explain the project and DNA testing better than I can, and if you decide to participate, he will contact the testing agency and make the arrangements. I recommend the 25 marker test because it is significantly more accurate than the 12 marker test. When the test kit arrives in the mail, it will contain instructions and an invoice. The discounted price for the 25 marker test was $169 plus postage when I signed up. I thought it was somewhat expensive, but now I believe it was a very worthwhile investment. Note: familytreedna.com now offers a 37 marker Y-DNA test for $169 plus postage.