Reversion to the mean happens because the phenotype is an imperfect proxy for the genotype, so if you select a person with phenotypic IQ of 130, maybe their genotypic IQ is only 124, and therefore their offspring with an IQ 100 person would only be IQ 112 in expectation.
However, this expectation applies to both the offspring’s genotypic and phenotypic IQ, so this is the only regression to the mean you’re going to see; it’s not going to regress further down the line.
Reversion to the mean happens because the phenotype is an imperfect proxy for the genotype, so if you select a person with phenotypic IQ of 130, maybe their genotypic IQ is only 124, and therefore their offspring with an IQ 100 person would only be IQ 112 in expectation.
However, this expectation applies to both the offspring’s genotypic and phenotypic IQ, so this is the only regression to the mean you’re going to see; it’s not going to regress further down the line.