3 ms·

Paper claims an conservatively estimated prevalence of 1/3652 for extreme inbreeding which equates to about 18k people, assuming a UK population size of 66 mill

Paper claims an conservatively estimated prevalence of 1/3652 for extreme inbreeding which equates to about 18k people, assuming a UK population size of 66 million. Not great, but nothing world-ending.

iguy 7y ago
And defines this to mean double-first-cousins and closer (perhaps this is standard). Also, as far as I could skim, this is the prevalence today, rather than an estimate of long-run prevalence. They must surely have data on simple first cousins, but it didn't jump out at me.
- blueblimp 7y ago
  For traits, the effect on non-double first cousins can be linearly approximated, which (as far as I know) is a good approximation for inbreeding depression. For example, taking Fluid Intelligence Score (basically how smart you are), in Table 3, its extrapolated effect size is -3.43, so: First cousin (relationship coefficient 0.125, inbreeding coefficient 0.0625) would give -0.214 to FIS. To put that in context, for medication, that would be considered a small effect size. So inbreeding at that level is a bit like taking a stupid pill.
- wyattpeak 7y ago
  Simple first cousins have a coefficient of relationship of 0.125, which is below the threshold considered in the paper. Received wisdom is that a coefficient below 0.25 doesn't cause serious deleterious effect. I have no idea if that's well supported, but I imagine it's relevant to why it wasn't studied.
- deleted 7y ago
  [deleted]
- azernik 7y ago
  The motivating force for this definition is uncles/aunts and closer; it just so happens that double-first-cousins have the same genetic relatedness as double first cousins.
Retric 7y ago
It’s also not always about intentional inbreeding. Many people don’t know who their biological parents are. While not a significant issue with adoption, if a guy has multiple kids who don’t know their siblings in the same area. Then they are likely geographically close and of similar ages...
- dmckeon 7y ago
  “Johnny be Fair” https://mainlynorfolk.info/folk/songs/johnnybefair.html https://mainlynorfolk.info/folk/songs/johnnybefair.html

iguy 7y ago

And defines this to mean double-first-cousins and closer (perhaps this is standard). Also, as far as I could skim, this is the prevalence today, rather than an estimate of long-run prevalence. They must surely have data on simple first cousins, but it didn't jump out at me.

blueblimp 7y ago
For traits, the effect on non-double first cousins can be linearly approximated, which (as far as I know) is a good approximation for inbreeding depression. For example, taking Fluid Intelligence Score (basically how smart you are), in Table 3, its extrapolated effect size is -3.43, so: First cousin (relationship coefficient 0.125, inbreeding coefficient 0.0625) would give -0.214 to FIS. To put that in context, for medication, that would be considered a small effect size. So inbreeding at that level is a bit like taking a stupid pill.
wyattpeak 7y ago
Simple first cousins have a coefficient of relationship of 0.125, which is below the threshold considered in the paper. Received wisdom is that a coefficient below 0.25 doesn't cause serious deleterious effect. I have no idea if that's well supported, but I imagine it's relevant to why it wasn't studied.
deleted 7y ago
[deleted]
azernik 7y ago
The motivating force for this definition is uncles/aunts and closer; it just so happens that double-first-cousins have the same genetic relatedness as double first cousins.

Retric 7y ago

It’s also not always about intentional inbreeding. Many people don’t know who their biological parents are. While not a significant issue with adoption, if a guy has multiple kids who don’t know their siblings in the same area. Then they are likely geographically close and of similar ages...

dmckeon 7y ago
“Johnny be Fair” https://mainlynorfolk.info/folk/songs/johnnybefair.html https://mainlynorfolk.info/folk/songs/johnnybefair.html