We can say exactly that if your parents have IQ of X points the kid will average complicated-formula IQ points.
Do we?
Pretty much. This falls out of the heritability research. One parent with IQ X, another with IQ Y, a known heritability of Z%, keep the environment constant, and some formulas later you have your probability distribution for the kid’s IQ.
Okay—in that case, I agree that if we already know the value of Z then why exactly it has that value isn’t relevant.
Do we?
Pretty much. This falls out of the heritability research. One parent with IQ X, another with IQ Y, a known heritability of Z%, keep the environment constant, and some formulas later you have your probability distribution for the kid’s IQ.
Okay—in that case, I agree that if we already know the value of Z then why exactly it has that value isn’t relevant.