I share your general concern, but would like to point out that this particular example couldn’t happen in human genetics for a variety of reasons (we are less c

I share your general concern, but would like to point out that this particular example couldn’t happen in human genetics for a variety of reasons (we are less consanguineous, practice assortative mating, get extensive medical care including fertility treatments). A bigger issue would be one particular implementation of genetic testing taking off in a group of humans who might otherwise be expected to produce offspring together. Perhaps - community of wealthy families all ordering the same IQ boosting agent may find that their grandchildren all share some unusual, genetically recessive ailment.