Short tandem repeats, or STR’s, are small pieces of junk DNA that have developed hiccups. Junk DNA has no function in terms of telling cells how to develop and what to do. Over billions of years a lot of genetic code evolved that no longer has any purpose in human cells. STR’s are small pieces of junk DNA that repeat themselves. For instance, AGTAGTAGTAGTAGTAGTAGTAGTAGTAGT. The value of an STR marker is the number of repeats; in this case, 10. This value is also sometimes called an allele. STR markers have names, like DYS 392. Every once in a while, the number of repeats on a marker changes. Over time, a lot of changes accumulate. If you take a number of such markers, like thirty seven, or forty, or sixty seven, then only men who are very closely related to each other are likely to have a set of markers that is very similar to each other. A group of STR’s is called a haplotype. A haplotype will consist of a list of marker names, each with the number of repeats.
A Y DNA report on STR markers looks like the following example. Under each marker name, or DYS #, is the “allele”, or the number of times the short piece of genetic code is repeated.
What you can do with STR markers
A father and a son usually have identical haplotypes or haplotypes that at most have just one difference. If two men share a common ancestor four or five hundred years ago, there might be a few small differences between them in haplotypes. People who aren’t related at all will have a lot of differences between their haplotypes. One can look at two haplotypes, and tell if the two men are likely to share a recent common ancestor.
STR markers can help with several kinds of genealogical questions. .
- It can tell if several male lineages are related. Often people want to know if several families with the same name with shared history, such as the same rare surname, or a history of having the same surname and lived in the same small and isolated place, were related. Comparing Y DNA of male line descendants of those families can answer this question. For instance, atleast two of my three Miller ancestors who settled in New Garden Pennylvania, early in the 18th century, were of the same male lineage. Two of my Hubbard ancestors in Connecticut, both named George, who treated each other as if they were cousins, were of the same male lineage. However, two Raymond families who lived near each other in a very small, isolated and very early Massachusetts village probably were not related. We cannot be sure because no two men claiming descent from Richard Raymond have proven to have the same Y DNA as each other or William and John Raymond, and it is possible that neither of them are male line descendants from Richard Raymond.. They could belong to other Raymond lines or have nonpaternity events in their lines (where a child was not biologically fathered by the man from whom he got his last name).
Y DNA STR markers can show the place of origin of a family. For example, Doolittle is an unusual name. Y DNA proves that all Doolittle families worldwide come from Kidderminster, England. Today’s lines cannot be connected with existing documents; however, historical documents show that the family has lived in that area since the 12th century. They began as serfs, then were free farmers, then were weavers and textile merchants in Kidderminster
Documents in Scotland, and the distribution of the name McKinstry over time in Scotland, strongly suggest that everyone of this name descends from a single family who lived in two parishes on the Cree River, in southern Galloway, southwestern Scotland, in the 15th century. The few bmd records on this family suggest that there were sometimes nonpaternity events, where unmarried mothers passed their McKinstry surname to their offspring. Nevertheless, Y DNA should help determine if people with this surname have a common origin, Since some McKinstry’s still live in Galloway or know for a fact that they come from there, Y DNA could connect other McKinstry lines to the same location. Y DNA could also distinguish if some McKinstry’s, such as the family of Rev. John McKinstry, or all New England McKinstry’s, who may have been related, have a different origin entirely. The fact that one of them has southwestern Scottish Y DNA makes the latter relatively unlikely.
Y DNA STR markers can also sort out how people are related within a family group. For example, their haplotypes clearly show that two Doolittle families are atleast a couple of hundred years more closely related to each other than they are to the third family. The Doolittles actually were first found in records of the Kidderminster area before 1200, and regularly thereafter. A family genealogist and author of a book on the Doolittles, had used the scanty records from Kidderminster to try to figure out how the lines were related to each other. The STR haplotypes forced her to reconstruct her chart. The families were related differently than she thought they were.
Since haplogroup I has a much slower mutation rate than the Doolittles’ R1b1b2, it could be harder to use McKinstry haplotypes to construct a hierarchical family tree. Nevertheless the family group dates to atleast 1500, and I am hoping that the entire family tree isn’t going to consist of Y DNA matches that are exactly alike. Small differences may allow knowing which families are more closely related to each other, and offer evidence, for instance, for who is and is not descended from good ol’ Roger.
Y DNA can be used to show who someone’s ancestors were. In many places, birth, marriage and death records only began to be kept very recently. For instance, most people who have ancestry from the 18th or 19th century in the Midwestern U.S., or in Ireland, cannot trace their ancestry. Some groups, particularly the Scotch Irish, tended not to keep very good family records, of the sort that families who valued their traditions kept in family bibles. My former housemate, Calvin Brewer, belongs to a big family group that could only trace their origins as far as 19th century Arkansas. Y DNA testing proved that they are descended from someone who owned a small plantation in Virginia in the 17th century. That is a large family with many descendants, most of whom can only be connected to their ancestor by Y DNA.
Sometimes STR haplotypes can show where a male line ancestor came from far back in time. Distant origins are more the job of SNP mutations, but sometimes STR markers are as strongly indicative of geographical origins. For example, my father’s Thompson line have a distinctively eastern haplotype of R1b1b2, that is confined to the plains of eastern Europe and southwesternAsia. But the Thompsons’ family history, written by their emigrant ancestor in the Quaker records where they settled, tells us that they in a village four miles south of the city of York, in England, which they left in the mid 17th century. However, when the Romans ruled Britain , 1600 to 2000 years ago, they founded York as one of their two administrative capitals in England . Over time thousands of soldiers were headquartered there, and roads came to York from every direction. Large numbers of the soldiers the Romans brought to Britain came from the plains of eastern Europe and southwestern Asia . When they finished their terms of service, the Romans often gave them land in England, especially in northern England where York was, to pay them for their military service, and to help subdue the native people. The latest King Arthur movie is about a very similar group of Roman soldiers from southwest Asia who ended up in northern England. (The foundation of a British ethnic identity was hardly that simple an affair.)
The following Y DNA results for McKinstrys who have done Y DNA testing at Family Tree DNA, support thinking that McKinstry is a single lineage surname (all four families share a single haplotype), tells us where the family is from, and show the beginning of a family tree.
This table shows among other things that William McKistry of Sturbridge really came from Carrickfergus. Vaguely cited family history said he was from there. Robert McKinstry of Meigs Co Ohio was also said to have come from Carrickfergus. At 37 markers Robert appears to be more closely related to the Sturbridge McKinstrys than the Sturbridge McKinstrys are to each other. At 67 markers they are all two off from each other.
The Bucks County McKinstrys are slightly more distantly related to the Carrickfergus McKinstrys.
The South Carolina McKinstrys are closely related to each other, but separated by two or three centuries from the Carrickfergus McKinstrys. Their ancestor certainly went to Ireland independently from Scotland.
The Y DNA of certain McKinstry families could help to place the entire group in a family tree, by virtue of distinctive aspects of their history. The father of Rev. John McKinstry is alleged to be ancestral to every McKinstry who has ever lived in Ireland. The existence of another McKinstry in the Ballyclare area of County Antrim, who was born before John McKinstry's father, disproves that. This means that the Y DNA of Rev. John McKinstry's descendants, and the Y DNA of male line descendants of the Ballyclare family, would be a real help to sort out the entire tree. If McKinstry's who still live in Scotland and never left have the same Y DNA, that would prove the present McKinstry's came from Scotland. So far all McKinstry's who can be found in Scotland and asked, have immediate ancestors who lived in Ireland.
Usually some members of an old family group like this do not match in YDNA due to historical nonpaternity events, such as adoptions, rapes, and extramarital and premarital affairs, and there could even be several main Y DNA lineages.
The haplotype shared by the McKinstry famlies above belongs with greater than 99% certaintly to the Isles-Scottish haplotype cluster. This haplotype cluster is likely to have originated in Galloway, Scotland, around 300 AD. During Roman times southern Scotland was heavily occupied and completely controlled by the Romans. They ran military lines along two routes, by which they also effectively controlled the border area. Galloway was isolated and rather a backwater. The Isles-Scottish haplotype benefitted from a founder effect early in its history; it was isolated in an area of small population and able to establish itself. The rest of the border region was far too busy and full of people migrating about in both directions. Today the Isles-Scottish haplotype is strongly concentrated in Galloway and northeastern Ireland. However its parent SNP's, L126 and L137, did not become established in Ireland, meaning that their daughter clade is unlikely to have been born there. The Isles-Scottish haplotype originated in Galloway. So the Y DNA evidence agrees with the historical documentation that this family is from Galloway.