DNA Testing

For many years the members of my Jordan family believed that they were descendants of the Samuel Jordan who sailed in 1609  from Plymouth, England on the ship Sea Venture, shipwrecked off Bermuda, and continued on to Jamestown in 1610.  This was the story as it appeared in a History of Halifax County Virginia by Wirt Johnson Carrington,  published in 1924.

Influenced in part by my own historical interests, my son Stuart McGuire Jordan developed a very active interest in genealogy and began to search family history in depth, examining census records, deeds, court records, etc.  He was very meticulous in his research, but his efforts were sometimes handicapped by the destruction of so many court houses and public records in eastern Virginia during the American Revolution and later in the Civil War.  Nevertheless, he began to develop a rather complete story of how and when our ancestors arrived in tidewater Virginia and eventually moved on to Halifax County.  Early-on, Stuart discovered that the Carrington history was full of errors.  There was no clear line of descent from Samuel Jordan of Jamestown to Henry Jordan, our first known ancestor, who arrived in Halifax County in 1778-9.  In fact, Stuart began to wonder whether we were even related to the Jamestown Jordans.  To learn the truth, Stuart decided to subject himself to a DNA test. He used a cheek swab and sent the results to one of the companies that advertises its genetic testing expertise.  Stuart initially asked for Y-DNA testing.

A man’s patrilineal ancestry, or male-line ancestry, can be traced using the DNA on his Y- chromosome (Y-DNA), because the Y-chromosome is transmitted father to son nearly unchanged. A man’s test results are compared to another man’s results to determine the time frame in which the two individuals shared a most recent common ancestor, or MRCA, in their direct patrilineal lines. If their test results are very close, they are related within a genealogically useful time frame.

Stuart’s DNA test results were compared those of others known to be descendants of the Jamestown Jordans.  This comparison proved that we are definitely related to Thomas Jordan, presumed grandson of Samuel Jordan of the Sea Venture.

These tests provided the answer to Stuart’s question about a relationship, but it did not establish a line of descent.  Additional years of diligent research led Stuart to conclude that Samuel Jordan of Jamestown is not our direct ancestor.  He now believes that our family descended from a brother or cousin of Samuel who came to America from Devonshire or Dorsetshire, England, sometime after the initial settlement at Jamestown.

Because surnames are passed father to son, Y-DNA tests are usually best for establishing familial relationships; but other types of DNA testing are available.  Autosomal tests look at chromosomes 1–22 and X. The autosomes (chromosomes 1–22) are inherited from both parents and all recent ancestors. The X-chromosome follows a special inheritance pattern. Ethnicity estimates are often developed from this sort of testing.  In other words, the testing company will give you an estimate of the percentage of your ancestors who came from Ireland, Germany, etc.  The accuracy of these estimates is somewhat suspect and is largely dependent on the breadth and size of the testing company’s data base.  Another type of DNA test is the Mitochondrial or mtDNA test.  It looks at the mitochondria, which is inherited from mother to child, and it can be used to explore one’s direct maternal line.

Before subjecting yourself to DNA testing, it would be advisable to study the subject in greater depth.  Also, be careful in your selection of a testing company.

 

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