> Isn't it true that children regress toward the norm?
There isn't perfect heritability of all traits because they are influenced by multiple genes. Two tall people likely have different genes that are making them tall, and there are likely interactions happening with other genes in their genome. When you get a child, they have some genes from each parent but they also get lot of novel interactions between the genes of tallness and the rest of their genome. This tends to reduce the heritability of traits that are modulated by complex interacting gene networks.
But it isn't a regression to some imaginary norm, it just means that that genes are not simply additive, they context dependent. But if you were to isolate 100 tall people from the population and had them breed for generations, and 100 short people and have them breed for generations, their offsprings likely will continue different in height still, they will never regress to the same "norm" because there are more tall genes or short genes in their respective populations.
There isn't perfect heritability of all traits because they are influenced by multiple genes. Two tall people likely have different genes that are making them tall, and there are likely interactions happening with other genes in their genome. When you get a child, they have some genes from each parent but they also get lot of novel interactions between the genes of tallness and the rest of their genome. This tends to reduce the heritability of traits that are modulated by complex interacting gene networks.
But it isn't a regression to some imaginary norm, it just means that that genes are not simply additive, they context dependent. But if you were to isolate 100 tall people from the population and had them breed for generations, and 100 short people and have them breed for generations, their offsprings likely will continue different in height still, they will never regress to the same "norm" because there are more tall genes or short genes in their respective populations.