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| Aquileo Parra's birthplace in Barichara, Colombia |
Mass has kilograms, sound has decibels, energy comes in joules, and DNA segments can be measured with the centiMorgan, named after the geneticist Thomas Hunt Morgan. The International Society of Genetic Genealogists (ISOGG) defines a centiMorgan as "a unit of recombinant frequency which is used to measure genetic distance."
I'm still trying to fully grasp the science, but I find it interesting that a centiMorgan deals more with areas of a chromosome impacted by genetic recombination, and is not a more generic term to number genes (like "base pairs"). Since these DNA tests care about inherited differences, we have to look at parts of the chromosomes that changed.
Like many in the United States, I first heard the term "centiMorgan" in relation to presidential candidate Elizabeth Warren, who in 2018 revealed that she had 25.6 cM of Native American DNA across five segments, including one segment that is 13.4 cM in length. I will not get into Elizabeth Warren's claims of Native American ethnicity, but here are genealogist Roberta Estes and geneticist Razib Khan on Warren's DNA test results.
The Shared cM Project puts these centiMorgan amounts in perspective. A parent and child share an average of 3,487 cM, a grandparent and grandchild share an average of 1,766 cM, and so on. Once I get my DNA matches, the shared cM values can determine possible relationships.
I found a Colombian version of Elizabeth Warren's claims of Indian ancestry, in the memoirs of Colombian President Aquileo Parra (1825-1900). As a child, Parra heard from his mother that his father's side was "pure Spanish," but his mother's great-grandfather Rueda married the daughter of a Guane Indian cacique, or chieftain. Parra's aunt also overheard the story and made a face of disgust.
I am related to both sides of Aquileo Parra's maternal family. His grandfather Manuel Fermín Gómez Wandurraga (1751-1816) is the brother of three of my direct ancestors, and his grandmother Ignacia Rueda Díaz (d. 1831) is the sister of at least two of my direct ancestors. I found the identity of Aquileo's great-great-grandfather Rueda — Cristóbal de Rueda Sarmiento (1686-1747) — who did not marry a Guane Indian woman, but a probable mestiza named Micaela Gómez Farelo. Cristóbal de Rueda Sarmiento was also a mestizo, so perhaps the family story of Indian ancestry got muddled over the generations.
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| Aquileo Parra (1825-1900) |
Funny enough, my grandfather Rueda claimed that Aquileo Parra was his great-grandfather, saying Parra fathered an illegitimate daughter with a school teacher but never knew of her. My grandfather was a serial liar but if he was correct that Aquileo Parra is my great-great-great-grandfather, then I inherited a possible average of 200 cM from the Colombian president. Perhaps DNA testing will turn up a 4th cousin who has Aquileo Parra as a common ancestor and our potential shared average of 35 cM.
Questions? Comments? Please email me at ruedafingerhut [at] gmail.com.
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