Quite a lot of mutations are so lethal that they abort embryonic development, yes. This is a severe problem with organisms drawn from a narrow gene pool, like humans and corn, and less so with others. It’s worth noting that, if we consider these mutations in the argument, we have to consider not only the children who are born and are weeded out, but all of the embryos conceived and lost as well.
Given how few conceptions actually make it to birth, and how many infants died young before the advent of modern medicine, humans didn’t lose two out of four, they lost more like two out of eight-to-twelve.
Quite a lot of mutations are so lethal that they abort embryonic development, yes. This is a severe problem with organisms drawn from a narrow gene pool, like humans and corn, and less so with others. It’s worth noting that, if we consider these mutations in the argument, we have to consider not only the children who are born and are weeded out, but all of the embryos conceived and lost as well.
Given how few conceptions actually make it to birth, and how many infants died young before the advent of modern medicine, humans didn’t lose two out of four, they lost more like two out of eight-to-twelve.