Probably coincidental & random but I worked really hard on it & it turned up a potential heritage population that might solve a family mystery regarding two members uncompleted “deathbed confessions” so I’m super excited
(Both paternal Grandma & her sister said “
I have to tell you something about our family …” the night before they died & never had the chance to say what it was)
I’ve written about the theory behind it here before but not the actual math because I’d be embarrassed if I made a mistake (I am hyperlexic & I transpose numbers; have to double & triple check everything).
I just wanted to figure out how I was born with Rh negative (O -) blood type to Rh positive parents: It
is possible if you had a Rh negative grandparent on both your maternal & paternal side. But I didn’t. Sixteen first-cousins in my generation & I’m the only one who is Rh negative.
Most of the scientific research of the Rh factor started in the 1940’s. Positive is the dominant trait while negative is recessive & 85% of humans worldwide are positive.
During childbirth; when a Rh negative mother’s blood comes in contact with the Rh+ baby, her body would develop antibodies against Rh + blood. Until the late 1960’s, when a vaccine-like injection called Rhogam became available; the majority of Rh - women with Rh + partners would raise an “only child”. because subsequent Rh + siblings would likewise be exposed to mom’s blood during their birth & those antibodies would literally attack & kill that baby (called Hemolytic disease).
So; I experimented with an underwhelming formula using the family tree. Big drawback to this was that my mom was first gen American & the trail ran cold in the old country (Greece).
I had a whole three variables.
1. Was that ancestor an only child? If “no” that = 0%. “Yes” = 100%.
2.
Geographical incidence of Rh negative blood type in that ancestor’s native country (using an Rh factor incidence map). For example: Sub-Saharan & East Asian incidence in between 0%-4%. Mediterranean’s are 5%-9% & Nordic’s are 15-19%.
(
There are only 2 populations with a higher than 19% incidence of Rh - persons & those are the French Basque & Ashkenazi Jews. Neither of those groups were accounted for in our family.)
3. Ancestors chance of “giving me” my blood by probability of generation. For example; a parent would be assigned 50%. Grandparents got 25%, etc …
Then I couldn’t figure out what to do with the numbers
so I just found the mean of each individual’s 3 variables & ranked the ancestors.
For example: Mom: only child? No = 0%. Geographical country of origin; Greece = 4%. Generation probability = 50%.
Mom’s mean = 18.
Dad: only child? = 0% (no). Geographical = 19% (Ireland) Generation = 50%.
Dad’s mean = 23. Dad “wins”; on to paternal grandparents. And so on.
Generation 3’s “winner” was my paternal grandmother (one of the attempted deathbed confessors) with a score of 14.6 & that led me to her mother. Generation 4’s winner; the only “only child” found, born in 1883 with 2 subsequent siblings who died in early infancy.
Score = 43.8!
But she had 3 children that did not die within hours or days after birth; she was not my Rh negative donor, just a “carrier” of sorts. It had to be Generation 5’s winner: Her father; who fathered an only child & was also the only surviving child out of 3 siblings.
Problem: That’s generation 5. Mathematically speaking, there may be a small chance of my blood type coming from him but in the real world; dominant/recessive traits don’t work that way. And that probability gets cut in half anyway because I still need that allele from Mom’s side.
I needed a game changer; something so genetically strong it could trump 4 generations worth of dominant blood. So after all THAT it occurs to me to Google “surname + origin”.
And it comes up “Ashkenazi”.
Dad’s family has been in an uproar since this; especially my 86 yr old uncle who has published 1000+ pages of the family tree going back to the 1400’s; but never found it.
Since my formula was so simplistic, some of us are testing.
My DNA results are back & cross referenced via Gedmatch. I am 6.53% Ashkenazi.
Probably couldn’t duplicate these results in a million years with all the confounders (lack of maternal input, high infant mortality during some of those generations, etc) but I’m pretty elated at the moment!
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