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placing trace ancestors in time
Thursday, October 20 2022
Since the genomic database update at 23&Me that suggested that 0.2% of my genes are Gujarati Patidar, I've been thinking about who that ancestor was and how he or she came to find him or herself injecting genes into the gene pool of northwestern Europe. I figured I could get a rough estimate of when that Gujarati ancestor (assuming there was only one, as is likely) lived by figuring out what power of two gives me 0.2%. The absolute value of that number is how many generations ago that ancestor lived. Doing this calculation in my head, I came up with the number eight, which I then multiplied by 25 (widely accepted as good approximation as the average age difference between generations) to get 200, which means this ancestor lived about 200 years ago. For some reason I was sloppy and subtracted this from 2000 to get 1800 as the year that ancestor was born. But this process was filled with numerous errors, including the fact that I was born in 1968, not 2000.
So this evening after work, I thought I'd put a little more effort into this calculation by making a table of the percentages of genes I got from different ancestors (organized by closeness of familial relation) with information such as when these ancestors were born. I then started with the oldest generation for which I have birthyears of all my ancestors (great-grandparents, in my case) and calculated approximate generation spans from there, working all the way back to the percentage of relation that the Gujarati had contributed to my genes. Initially, since generations in my ancestors had tended to be longer than average, I used 30 years for the first unknown step backwards into the past, though after that I used 25 years (since, as with most exceptional traits among replicating organisms, they usually quickly revert to the mean). Doing this, I came up with a birth year of about 1700 for the Gujarati, who would be my great-great-great-great-great-great-great grandparent. Using this same methodology, I also placed the birth of my Coptic Egyptian ancestor at about 1725, the birth of an Italian ancestor at about 1775, and the birth of an ancestor in Eastern Europe at about 1800. Since I have actual birthdates for great grandparents as early as 1839, that gets us pretty close to known individuals. My thinking for now is that the Gujarati and Coptic Egyptian genes came in through my great grandmother Carolne Abbott, since she is the biggest mystery in my family tree, is always described by members of my mother's family as being "from Canada," and the other 23&Me customers with near-Eastern genes seem to be from somewhere near her part of the family tree.
Here's the chart I came up with:
| genetic contribution percentage | who | year born | possible trace ancestor | relation | methodology |
| 100 | Gus Mueller | 1968 | | self | |
| 50 | Elizabeth DeMar | 1937 | | mother | |
| 50 | Robert Mueller | 1923 | | father | |
| 25 | Margaret Ilsley | 1896 | | maternal grandmother | |
| 25 | Clarence DeMar | 1888 | | maternal grandfather | |
| 25 | Katherine Deschler | 1890 | | paternal grandmother | |
| 25 | John Mueller | 1881 | | paternal grandfather | |
| 12.5 | Sarah Barlett Lobdell | 1872 | | maternal great-grandmother | |
| 12.5 | Charles Danforth Ilsley | 1865 | | maternal great-grandfather | |
| 12.5 | Caroline Abbott | 1869 | | maternal great-grandmother | |
| 12.5 | George Washington DeMar | 1856 | | maternal great-grandfather | |
| 12.5 | Lena Putz | 1854 | | paternal great-grandmother | |
| 12.5 | William Deschler | 1854 | | paternal great-grandfather | |
| 12.5 | Anna Maria Schneider | 1848 | | paternal great-grandmother | |
| 12.5 | Johannes Mueller | 1839 | | paternal great-grandfather | |
| 12.5 | | 1857 | | average birthyear of great-grandparents | |
| 6.25 | | ~1827 | | great-great grandparent | subtract 30 years because generations tend to be longer in my family |
| 3.125 | | ~1803 | Eastern European | great-great-great grandparent | subtract 25 years, reversion to mean of generation length |
| 1.5625 | | ~1777 | Italian | great-great-great-great grandparent | subtract 25 years |
| 0.78125 | | ~1753 | | great-great-great-great-great grandparent | subtract 25 years |
| 0.390625 | | ~1727 | Coptic Egyptian | great-great-great-great-great-great grandparent | subtract 25 years |
| 0.1953125 | | ~1703 | Gujarati | great-great-great-great-great-great-great grandparent | subtract 25 years |
This evening Gretchen made a big pot of potato-kale soup, to which I added bits of poblano pepper and oyster crackers, and it made for a great chilly-weather dinner. We watched another episode of Bad Vegan with increasingly alarm as obvious psycho conman Anthony Strangi led Sarma Melngailis down his rabbit hole of madness and manipulation. Watching all the wire transfers flip by, the ones Anthony managed to get Sarma to send him, reminded me of all those IOUs my mother wrote to Sara Kesterson, though that scam was an order of magnitude smaller.
For linking purposes this article's URL is:
http://asecular.com/blog.php?221020 feedback
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