unfortunately for the larger-than-normal percentage of children born with birth defects and genetic abnormalities, first cousin marriage is extremely common in pakistan:
another example of what happens when you have a relatively small population group that marries and reproduces only within their own community, repeatedly for 1000+ years, there's a large number of genetic disorders which disproportionately affect ashkenazi jews:
to the extent that ashkenazi are strongly encouraged by their family doctors to go for special genetic screening, as a routine part of family planning.
https://www.google.com/search?client=ubuntu&channel=fs&q=fir...
another example of what happens when you have a relatively small population group that marries and reproduces only within their own community, repeatedly for 1000+ years, there's a large number of genetic disorders which disproportionately affect ashkenazi jews:
https://www.google.com/search?client=ubuntu&channel=fs&q=ash...
to the extent that ashkenazi are strongly encouraged by their family doctors to go for special genetic screening, as a routine part of family planning.