Using DNA with LDS Pioneer Ancestors
DNA has changed the way genealogists can research their family, providing a new type of source. But using DNA to answer genealogical mysteries can be more complicated for people who descend from early LDS Pioneers. This article explores some of the common challenges encountered when researching pioneer ancestors using autosomal DNA.
Genetic Genealogy Basics
MyHeritage, Ancestry, 23andMe, and FamilyTreeDNA all offer tests for Autosomal DNA (atDNA), which looks at all chromosomes and includes DNA inherited from all ancestral lines.[1] A child receives 50% of their DNA from each parent (half from egg, half from sperm), and that implies 25% from each grandparent, and 12.5% from each great-grandparent, and so on. However, in reality, the randomness of DNA recombination in the creation of egg and sperm means that most people have about 25% of each grandparent, but they may have just 24% of grandfather and 26% of grandmother. Because of this randomness of inheritance over multiple generations, starting about five to six generations back, it is possible to have actual ancestors for whom a test taker carries none of their atDNA.
DNA is measured in centimorgans (cM), and genealogists use the Shared cM project to estimate the range of shared DNA expected for a specific relationship.[2] A first cousin will typically share about 866cM of DNA (the range is 396cM to 1397cM), a half first cousin (sharing just one grandparent) would share about 449cM, and a second cousin (shared great-grandparents) will share about 229cM, and so forth.
The Shared cM project numbers are all based on matches who share only one common ancestor (half cousins) or ancestral couple (full cousins). Descendants of early LDS Pioneers often find they share multiple ancestors, or they descend from very complex family relationships created by the practice of polygamy. Some of the more common conditions are described below, along with their effect on the DNA analysis.
Pedigree Collapse
Sometimes people refer to the early Pioneers as endogamous, which is not quite true. Endogamy occurs when a community repeatedly intermarried with one another for centuries. The best-known example of endogamy is Ashkenazi Jews, who for centuries only married within the tribe for religious, cultural, geographic, and social reasons. A person of 100% Ashkenazi descent will find that all of their DNA matches all match each other because they all share multiple ancestors. Other well-known endogamous communities are Icelandic people, and Polynesians, who intermarried for generations because of geographic isolation.
The early members of the Church of Jesus Christ of Latter-day Saints were not endogamous, although for reasons of religion and geography the children of early pioneers did tend to intermarry. The result is that one cousin may be related to another cousin through two different sets of grandparents. In the case of Church members, generally by the second and third generations, the population was large enough that the effect was not long lasting. A situation where a cousin shares a few great grandparents would be pedigree collapse (not enough great-grandparents); endogamy is when cousins share many, many ancestors on multiple lines.
The chart below visualizes the pedigree of someone with 100% Church Pioneer ancestors.[3] Notice most of her ancestors form distinct ancestral lines, but one group—highlighted in the green box—has some pedigree collapse where cousins married.
It is quite common to find this sort of pedigree collapse among ancestors who lived in small villages and rural places, regardless of their religious practices. The descendants of people who settled in Appalachia and in the western reaches of the early United States will frequently have a pedigree that looks similar to the chart above. There simply were not enough families to avoid it.
When pedigree collapse is found in DNA matches, the safest approach is to not use those matches in the analysis. However, if it is vital for the research question to work with pedigree collapse, there are some methods to try. If the DNA matches are from the MyHeritage, 23andMe, or FamilyTreeDNA, it is possible to examine matches’ detailed segment information, and work to map specific segments of DNA to a specific ancestor. That process is time consuming and an advanced skill that is beyond the scope of this article, but it is useful to know that it is sometimes possible.
Double Cousins
One of the more common DNA issues to arise with Pioneer descendants is finding double cousins. Members of the Church of Jesus Christ of Latter-day Saints did not practice cousin marriage, but because most pioneers lived in small towns, many of their descendants find they match someone along multiple ancestral lines.
This pedigree is simplified for clarity. In this case Helen Davis and Susan Barnes are double second cousins, because they share the same two sets of great-grandparents. This is not pedigree collapse as both Helen and Susan have the right number of great-grandparents.
Pioneer descendants often find double, even triple, cousins in their pedigree. The effect on the DNA is that two matches will share more cM than expected. For example, in a real case, two double second-cousin descendants of Pioneers who settled in rural Idaho share 461cM of DNA; the average for a second cousin match is 229cM. According to the shared cM project, 461cM has an 87% chance that they are half first cousins (share one grandparent), or half 1C1R (one test taker is a generation younger), or a great-great-aunt/uncle.
It is important to note that the relationship estimates the testing companies use do not take double-cousins into account. In this case, Ancestry’s Thrulines and new Cluster tool each identified one set of shared great-grandparents and ignored the other set. The same is true with MyHeritage’s Autocluster tool – it will pick just one cluster to group the matches with and does not account for double cousins. Without knowing they are double cousins, that could mislead a researcher and lead to wrong conclusions. The high amount of shared DNA was the clue that they were likely at least double cousins and sparked documentary research to find the common ancestors.
As with pedigree collapse, the easiest way to research when this occurs is to ignore double cousins. However, if they cannot be ignored, there are some methods. The most accurate way is to analyze the individual segments inherited by each match, as mentioned for pedigree collapse. There are also a few “quick” methods. One rule of thumb is to assume a half or full generation further back than the amount of DNA indicates for double-cousin matches. A full step back from first cousins leads to second cousins and that can be used to approximate how far back in the tree these two test takers share ancestors. Another approach is to add the expected amount of DNA for each relationship, then divide by the number of matches, but this assumes the test takers’ pedigrees are already known. Both of those quick methods can lead to low accuracy and can lead to misinterpretation, and in the end the best approach is to build the matches’ pedigrees to identify all shared ancestors.
Polygamy
One cannot talk about early LDS Pioneers without discussing polygamy. While it is true that a majority of Church members did not practice polygamy, it is also true that it had far reaching effects. The Church of Jesus Christ of Latter-day Saints published an essay on polygamy that stated about half of members living in Utah Territory in 1857 experienced polygamy, either as a spouse or a child.[4] That percentage declined over time as more people moved to Utah, and by 1870 scholars estimate about 25 to 30 percent of Utah residents experienced polygamy.
The effects of polygamy on DNA analysis vary significantly depending on family construction. Most polygamist men had only two or three wives, and those women usually were not related to each other. Using DNA in that case is very straightforward, as descendants share half-relationships. The grandchildren of the male polygamist will be either full or half-first cousins, depending upon which wife was their grandmother.
Some polygamist men married women who were sisters. In that case, the children of those marriages will appear to be full siblings in the DNA results, and their descendants will appear to be full cousins. All of the children of those unions share the same four grandparents. The two wives who are sisters do have different DNA, and an ambitious advanced project would be to map the segments to each mother. If a descendant were unsure which sister is the mother of their ancestor, then the segment mapping approach may be useful. It is most helpful if one of the sisters had children with another spouse, because that can help identify which DNA segments she has passed down and distinguish her. Usually, that type of time-consuming deep study is not necessary to answer genealogical questions, and it is typically best to rely upon documentary evidence to understand which children belong to which wife.
The type of polygamy many people think of when they hear the word is that practiced by Brigham Young and other early Church leaders who had many, many wives. Early Church Apostle Parley P. Pratt had 12 wives and 30 children, 266 grandchildren, and is believed to have from 30,000 to 50,000 living descendants. The great challenge with using the DNA for a descendant in this situation is the volume of matches. One descendant of Parley P Pratt has over 500 DNA matches who descend from him. It is difficult to work with so many matches if the goal is to identify those who come from a specific wife. Furthermore, often the genealogical question is to find ancestors beyond the polygamist. In that case, it is hard to find matches who descend from a generation or two back, because they are buried in the hundreds of polygamist matches. There are no easy tricks for this, as it just takes dedicated research among the matches and building their pedigrees.
Conclusion
The complex family relationships of early LDS Pioneers, along with the fact that they tended to live in small communities with few choices for marriage partners, means that descendants can face some difficulties when using DNA to solve questions. Fortunately, it is not impossible, and being aware of the ways that DNA is affected can help researchers avoid simplistic and wrong conclusions.
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Karen
Images:
| Images: 1. C.C.A. Christensen, Leaving Missouri. Source: Wikimedia Commons 2. Chart made with the tool found here: https://learnforeverlearn.com/ancestors/. 3. Chart made by the author 4. Ira Eldredge and his Three Wives, Nancy Black, Hannah Savage, and Marie Andersen. Circa 1864. Source: Wikimedia Commons 5. Parley P. Pratt Wikimedia Commons |
[1] They all test all 23 chromosomes, but Ancestry and MyHeritage do not make information available for the 23rd, which is the XY sex chromosome; they use the other 22 chromosomes for matching and analysis. As the name suggests, 23andMe presents all 23 chromosomes, as does FamilyTreeDNA. FamilyTreeDNA also offers Y-DNA and mt-DNA tests, which will not be discussed in this article.
[2] The Shared cM project was created by Blaine Bettinger, a genetic genealogist with a PhD in biology. The tool, along with links to the scientific detail, can be found here: https://dnapainter.com/tools/sharedcmv4.
[3] Chart made with the tool found here: https://learnforeverlearn.com/ancestors/.
[4] “Plural Marriage and Families in Early Utah,” The Church of Jesus Christ of Latter-day Saints, (https://www.churchofjesuschrist.org/study/manual/gospel-topics-essays/plural-marriage-and-families-in-early-utah?lang=eng).