*Validation of genealogical lineages using DNA

The genealogist builds structures based on documentary research but these structures do not always correspond to biological reality. They may perfectly reflect events revealed by Baptism, Marriage and Burial records (BMS) but they can still not really reflect what happened at the biological level. Non parental events (NPEs) regularly occur and BMS records cannot always attest of their occurrence. Adoption, silent assimilation, name change, illegitimate child, etc, and many other events, distort reality without the genealogist being aware of this by simple examination of the available documentation. It is here that genealogy using DNA can attend documentary genealogy through the validation or invalidation of some of the lineages that make up a genealogical structure that was originally built from BMS records.

In a genealogy, such as the one illustrated as a fan at Figure 1, each lineage is either a matrilineage or patrilineage for individuals located at the core of the structure. Two principles of DNA transmission can be applied by the genealogist to validate matrilineages and patrilineages. The first principle regards the transmission of mitochondrial DNA (mtDNA) which follows the uterine or matrilineal line. The mtDNA signature of a person is that of his or her ancestors in matrilineage. Recall that both men and women receive their mitochondrial signature from their biological mother.
The second principle concerns the transmission of the DNA of the Y chromosome (yDNA) in males. This transmission is from father to son integrally along the line of fathers or patrilineage.

The empirical implications of these laws are thus amenable to a test within a given genealogical structure. A woman or a man should show the same mtDNA signature as his or her mother, the mother should possess that of her mother and so on back in time until a most distantly known matrilineal ancestor or matriarch is reached. A man in a genealogical structure should show the same yDNA signature as his father, the father should have that of his father and so on until the most distantly known ancestor in patrilineage called the patriarch is reached.

Figure 1 shows a constant eight generations back to the the matriarch or the patriarch but in reality this number of generations will vary from one lineage to another within a given genealogical tree. This figure uses the Sosa-Anhentafe-Stradonitz numbering system is used. For instance, the cujus is #1, his or her father is #2 and #3 is his or her mother. The matriarch of #1, along his or her matrilineage, is m1. The matriarch of #2 is m2. The patriarch of #6 is p6. And so on.

The task of the genetic genealogist will thus be to systematically compare the DNA signatures possessed by individuals at or around the de-cujus or that of their immediate descendants to that of their most remotely known ancestors, matriarch or patriarch, situated at the periphery of the fan.


Figure 1. Fan illustrating the various lineages that can be validated through DNA testing. Gray-blue stands for men and pink for women. The ancestors in matrilineage and patrilineage are found at the periphery of the fan. Individual m1 is the ancestress in matrilineage of #1; p1 is the patrilineal ancestor of #1. The cujus is #1. Sosa numbering is used. For instance, when a perfect match is obtained between the mtDNA signature of #1 and that of his or her matriarch m1, lineage #1 to m1 becomes validated. Similarly, when there is a match between the yDNA signature of #1 and that of his patriarch p1, then the lineage #1 to p1 is considered valid. A woman does not possess yDNA. Thus if #1 is a women, her father #2, or her brother can serve as a substitute for her, providing the yDNA signature required to be compared with that of the patriarch of her line of men.

The signatures of persons at the core of the genealogical fan can be obtained by DNA testing them or by testing one of their descendant having the same remote ancestor in matrilineage or patrilineage depending upon the type of lineage tested. But the signatures of their matriarch and patriarch at the outer side have to be inferred through triangulation. Ideally for a given population of founders like that of French Canada and Acadians, a catalog of ancestral signatures would be available, each mtDNA or yDNA signature having been validated through triangulation based upon their contemporaneous alleged descendants. For instance at the French Heritage we are building such a catalog. But, in most cases, triangulation will have to be carried out in situ, that is using the signature of a person part of the studied genealogical structure (or a descendant) together with a least one descendant of the same patriarch or matriarch, but not participating to the studied family tree.


Figure 2. Triangulation of the signature of a Most Recent Common Ancestor (MRCA).

Triangulation of signatures for matriarchs and patriarchs proceeds as illustrated at Figure 2. A minimum of two signatures is required to triangulate on the ancestor. A first signature (A) may be that the person in the lineage to be tested. It could be #1 of Figure 1. The person that will provide the other signature (B) ought not to be part of the same lineage as (A), whilst having the same ancestor in matrilineage or patrilineage. On Figure 2, (A) and (B) share the same yDNA signature. Documentary research further shows that they descend from the same patriarch who is also their most recent common ancestor (MRCA). He is represented by the star on the figure. Note that they must descend from two distinct branches, sons or daughters of the MRCA. Given this double concordance (1) at the level of their yDNA or mtDNA signatures and (2) at the level of their respective documented ancestries which converge on their MRCA, the genealogist is justified to infer that (A) and (B) share the yDNA or mtDNA signature of their MRCA, that their signature is that of their patriarch (for yDNA) or matriarch (for mtDNA).

Naturally, if the signatures of (A) and (B) do not match, or that their respective ancestries do not converge on a common ancestor, the triangulation fails. Moreover, if (A) and (B) are not related within recent times, triangulation also fails and the signature of their presumed matriarch or patriarch cannot be inferred.
Validity is to what extent or probability the proposition « their signature is that of their MRCA » corresponds to reality. Triangulation does not guarantee in an absolute manner that the signature shared in common by (A) and (B) is that of the ancestor identified and documented in the family tree. However, it is most likely the ancestral signature when triangulation is carried out through two different sons, when yDNA is concerned, or two different daughters, when mtDNA is concerned. Validity can be further increased in the case of yDNA by converging on the MRCA through two different sons from two distinct marriages. Similarly for mtDNA, converging on two different daughters issued from two distinct marriages increases chances that the haplotype showed by the descendants be that of their ancestress. Coming from two different sons or daughters diminishes the chances that a NPE has occurred and coming from two different marriages of the same ancestors further decreases NPE as a confounding rival explanation. Picking a signature from a result table of a surname project at FTDNA on the basis of its most frequent occurrence shows no validity. It could be the signature of a very fecund raider. And calculating modal values is irrelevant to ascertain of the identity of the patriarch. Only triangulation carefully carried out can identify the potential patriarch or matriarch.


Figure 3. Validation of my own genealogy which is in progress. Six lineages have been validated so far and are shown in green. A seventh, that of Léon PROVOST, is shown in purple; it poses difficulty since the signature of the substitute does not match that of another alleged descendant having Martin PROVOST in patrilineage. The name of the ancestor is written in script font.

On Figure 3, m1 represents the signature of the King’s Daughter Jeanne FOURNIER from whom #1 alleged to descend based upon careful documentary research. Whatever the sexual gender of #1, his or her mtDNA signature should be that of m1. The signature of m1 was inferred through the in situ triangulation from the signature of #1 with a perfect Full Mitochondrial Sequence (FMS) match found at FTDNA whose matrilineage also converged upon King’s Daughter Jeanne FOURNIER.

Lineage #1 to m1 was thus declared valid in the genealogy of #1. Since #1 is a man, he should possess the yDNA signature of patriarch p1 of his patrilineage. The signature of p1 was known from independent triangulation and #1 perfectly matches that of p1, thus validating lineage #1 to p1. But suppose that #1 had been a woman. Women can test their patrilineage by asking their father or a brother who possess the Y chromosome they would have inherited if having been a male. The yDNA signature of #2, the father #1 (if female), or their sibling brother could be used in the comparison with that of the patriarch. Again, the concordance of this signature of #2 or that of the sibling with that of the patriarch in patrilineage could serve to validate lineage #1 to p1 in the genealogy of Figure 3.
Another lineage validation can be carried out using the father #2 and his own matriarch m2. If #2 can be tested, the comparison of his mtDNA signature with that of m2 would validate the lineage #2 to m2. In this peculiar case, the signature of m2 was inferred from in situ (in place) triangulation using #2 as a member of the comparison and another mtDNA FMS match found at FTDNA and whose ascendancy converged upon the same ancestress Marie FERRA. Now, suppose that #2 had passed away or did not want to participate, a sibling of #2, an uncle or an aunt of #1, could serve instead for this comparison.

This procedure is repeated for other lineages making up the most recent generations of the genealogy to be validated. When the corresponding member is deceased, a descendant can be used as a substitute. However, one must be aware that using substitutes increases the chances of NPE occurring, thus interrupting the the DNA chain attesting to the generation. Nonetheless, still finding a match would reveal the robustness of this link. Otherwise if it fails, the triangulation operation would have to be retried using another substitute.

Figure 3 shows the validation work in progress for my own genealogy. Lineages highlighted in green have been validated by a concordance between the signature of the person in my family tree and the matriarch in matrilineage or the patriarch in patrilineage obtained by triangulation in situ in most cases. Thus Figure 3 shows that the patrilineages of Jean DESLANDES-dit-CHAMPIGNY and Vincent BRO were also validated. Some other lineages were also tested but it becomes more and more difficult and risky to find direct descendants as one moves toward the periphery of the fan. The lineage highlighted in purple on Figure 3 poses me problem for the moment. My own documentation, as well as that of the descendant used as a substitute for testing have to be thoroughly checked.
While completing such a validation the genealogist gets reinforced when a lineage appears to be validated through DNA. It is always a satisfaction to see that our structure fits biological reality. On the other hand, when a lineage is not validated, it forces the genealogist to question the validity of his/her documentary work or sources, sometimes calling for a reorientation of research following the information given by DNA. For instance discovering that a lineage’s haplogroup is Amerindian could reorient the documentary research. It could also stimulate the elaboration of new explanations, leading to an enrichment of family history. On the whole, the structure which progressively gets shaped by knowledge from both documentary research and DNA verification gradually moves our genealogy towards the biological reality.

Completing and polishing a genealogy is also a social affair. The genealogist does not work alone. She or he is in contact with other researchers and the discoveries made in the context of genealogy validation through DNA can serve others and in turn can be used to complete a genealogical structure by incorporating information made available by others.

Firstly, triangulated mtDNA and yDNA signatures of ancestors should be cataloged and recorded in databases publicly available so that they become beacons for genealogical research and be available for the validation of lineages in other genealogies having these ancestors as well. As regards the founders of French Canada and Acadia, this cataloging task is in progress as part of the French Heritage DNA project (http://bit.ly/1bh9HmM). In addition, this information could eventually be incorporated into other databases such as the PRDH, which is the most complete databases related to founders of New France.

Secondly, lineages validated using DNA within a given genealogy could serve others to validate their own genealogies, provided the corresponding information becomes available in databases in a standardized and usable form. For instance whole validated patrilineages and matrilineages could become available as chains, or more simply as binary engendering information in the form of X begat Y, where begat would entail validated DNA transmission. Such binary engendering information once validated as part of lineages reaching the core of some genealogies could be used by other genealogists to validate lineages that are situated too far from their own core.

It is also conceivable that other forms of DNA, especially the autosomal and that of the X chromosome, will eventually serve to validate relationships in a genealogy.

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