Somali Founder Effect & Genetic Diversity

Thegoodshepherd

Thegoodshepherd

Galkacyo iyo Calula dhexdood
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It seems that the average Somali is more inbred than the product of a normal second cousin marriage, and FROH (measure of inbreeding) of 0.015 for children of second cousins and a higher higher 0.018 for the average Somali. This is apparently due to present day preference for consanguineous marriage among Somali because we have many long runs of homozygous DNA. Very shocking news to me because inbreeding lower intelligence by quite a lot. Children of first cousin marriages have iqs about 10 points lower than average. Our neighbors the Oromo and and Amhara have extremely low rates of inbreeding by world standards.

Somalis being a small ethnic group originally does not explain this outcome btw.
inbreeding 1.png
inbreeding 2.png


inbreeding 3.png


The 52.28 number is how many long runs of homozygosity (more than 1.5 Megabases) the average Somali has. Compare this figure to the Amhara and Oromo at 7.55 and 9.7.

The average Somalia has an FROH (measure of inbreeding) of 0.018 which is higher than children of second cousins, while the Amhara have levels 7x lower and the Oromo about 5.5x lower.

Almost half of all Somalis, 48.7%, are products of either first cousin marriage or second cousin marriage. Compare this to 0% of Oromo and Amhara!
This statistic blew my mind.

Source: https://sci-hub.tw/10.1007/s00439-019-02045-1
link.springer.com

Runs of homozygosity in sub-Saharan African populations provide insights into complex demographic histories - Human Genetics

The study of runs of homozygosity (ROH) can shed light on population demographic history and cultural practices. We present a fine-scale ROH analysis of 1679 individuals from 28 sub-Saharan African (SSA) populations along with 1384 individuals from 17 worldwide populations. Using high-density...
link.springer.com link.springer.com
 
Thegoodshepherd

Thegoodshepherd

Galkacyo iyo Calula dhexdood
VIP
My theory is that Somalis as an ethnic group, taken as a whole, have a sufficient effective population size. The problem in my opinion is that most Somali subclans occupy large areas of land which may make it hard to interact with people outside of your clan most of the time. So while the ethnic group as a whole has enough genetic diversity, the subclans are too small to provide the diversity needed to avoid inbreeding.
 
Sleepy Hollow

Sleepy Hollow

I wonder how the results of a study like this would turn out if done on other nomadic people, would they end up having similar levels?

Also on your hypothesis, doesn't it fall apart once we get to Hiiraan and below? The south is fairly diverse and even includes subclans who have been farmers for as long as they could remember existing so wouldn't those subclans have results that are divergent at a statistically significant scale compared to the rest?
 
Thegoodshepherd

Thegoodshepherd

Galkacyo iyo Calula dhexdood
VIP
Sleepy Hollow said:
I wonder how the results of a study like this would turn out if done on other nomadic people, would they end up having similar levels?

Also on your hypothesis, doesn't it fall apart once we get to Hiiraan and below? The south is fairly diverse and even includes subclans who have been farmers for as long as they could remember existing so wouldn't those subclans have results that are divergent at a statistically significant scale compared to the rest?
Click to expand...

The Somalis in this sample are all from Ethiopia.

Btw I don't consider D&M to be ethnic Somalis, especially the Digil. Tunni, Jiido, Dabarre, Garre etc... are in my opinion small ethnic groups.
 
Aurelian

Aurelian

Forza Somalia!
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Thegoodshepherd said:
It seems that the average Somali is more inbred than the product of a normal second cousin marriage, and FROH (measure of inbreeding) of 0.015 for children of second cousins and a higher higher 0.018 for the average Somali. This is apparently due to present day preference for consanguineous marriage among Somali because we have many long runs of homozygous DNA. Very shocking news to me because inbreeding lower intelligence by quite a lot. Children of first cousin marriages have iqs about 10 points lower than average. Our neighbors the Oromo and and Amhara have extremely low rates of inbreeding by world standards.

Somalis being a small ethnic group originally does not explain this outcome btw.
View attachment 125137View attachment 125138

View attachment 125146

The 52.28 number is how many long runs of homozygosity (more than 1.5 Megabases) the average Somali has. Compare this figure to the Amhara and Oromo at 7.55 and 9.7.

The average Somalia has an FROH (measure of inbreeding) of 0.018 which is higher than children of second cousins, while the Amhara have levels 7x lower and the Oromo about 5.5x lower.

Almost half of all Somalis, 48.7%, are products of either first cousin marriage or second cousin marriage. Compare this to 0% of Oromo and Amhara!
This statistic blew my mind.

Source: https://sci-hub.tw/10.1007/s00439-019-02045-1
link.springer.com

Runs of homozygosity in sub-Saharan African populations provide insights into complex demographic histories - Human Genetics

The study of runs of homozygosity (ROH) can shed light on population demographic history and cultural practices. We present a fine-scale ROH analysis of 1679 individuals from 28 sub-Saharan African (SSA) populations along with 1384 individuals from 17 worldwide populations. Using high-density...
link.springer.com link.springer.com
Click to expand...
But how normal second cousins have lower FROH rate, yet average Somali isn't 2nd cousin product.
 
Sleepy Hollow

Sleepy Hollow

Thegoodshepherd said:
The Somalis in this sample are all from Ethiopia.

Btw I don't consider D&M to be ethnic Somalis, especially the Digil. Tunni, Jiido, Dabarre, Garre etc... are in my opinion small ethnic groups.
Click to expand...
Your hypothesis makes a lot more sense now since it was Galbeed. Plus Somalis expanded very quickly into the region with a severe lack of infusion of new blood. Much of the Oromos driven out and women taken as conquest were assimilated Somalis themselves (with much of them lacking Oromo blood due to the ingenious Gada system that assimilates entire communities)

Your reasoning on D&M seems to be a bit of a cop out though. Have they had genetic results that differ to such an extent? I'm guessing some but not all of them to make such sweep generalizations, unless you very much attach being Somali to being a pastoralist.
 
Thegoodshepherd

Thegoodshepherd

Galkacyo iyo Calula dhexdood
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Ebuo said:
But how normal second cousins have lower FROH rate, yet average Somali isn't 2nd cousin product.
Click to expand...

The average Somali is genetically a product of second cousin marriage. If you keep marrying within your subclan, generation after generation, you will accrue enough homozygosity within that subclan such that any child from a marriage within that subclan is genetically inbred to a similar degree as the offspring of a second cousin marriage of unrelated people. Also keep in mind that first cousin marriage raises the FROH 4x more than a second cousin marriage. Many Somalis marry their first cousin.
 
reer

reer

VIP
Thegoodshepherd said:
The average Somali is genetically a product of second cousin marriage. If you keep marrying within your subclan, generation after generation, you will accrue enough homozygosity within that subclan such that any child from a marriage within that subclan is genetically inbred to a similar degree as the offspring of a second cousin marriage of unrelated people. Also keep in mind that first cousin marriage raises the FROH 4x more than a second cousin marriage. Many Somalis marry their first cousin.
Click to expand...
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