Although raising one child may provide experience, it does not guarantee success with the next child.

From The Checklist Manifesto: How to Get Things Right by Atul Gawande

Complex problems are ones like raising a child. Once you learn how to send a rocket to the moon, you can repeat the process with other rockets and perfect it. One rocket is like another rocket. But not so with raising a child, the professors point out. Every child is unique. Although raising one child may provide experience, it does not guarantee success with the next child. Expertise is valuable but most certainly not sufficient. Indeed, the next child may require an entirely different approach from the previous one. And this brings up another feature of complex problems: their outcomes remain highly uncertain. Yet we all know that it is possible to raise a child well. It’s complex, that’s all.

Gawande is illustrating the difference between simple, complicated and complex problems or tasks.  Raising children is an example of a complex task.  Past experience helps but is not determinative because every child is different and all circumstances are necessarily different.

But I think there is a much larger point here.  In the US, we have fallen prey to the intellectually indefensible approach of treating all differences between groups (race, religion, sex, ethnicity, class, etc.) as inherent evidence of obvious discrimination.

This is of course nonsense.  There are many reasons for variance in performance between groups having nothing to do with discrimination.  Indeed, in many fields, there is solid data supporting that differences in outcomes are definitely because of differences in choices rather than because of differences in discriminatory activity.

Nonsense though it may be, differential impact remains relevant until it is eventually and finally discarded.

But Gawande is pointing out another major factor.  We know that genetics is certainly a strong contributor both in terms of capability (height, weight, IQ, muscle strength, etc.) as well as in terms of behaviors.  This is no declaration for biological determinism but merely the acknowledgement that the overwhelming majority of evidence is against the blank slatism and that humans inherit some capabilities and many behavioral dispositions.  All of these dispositions are later bounded and constrained by cultural attributes.

Different cultures have different degrees to which they promote and reward marriage, family formation, children, marriage sustenance, and generational involvement in child rearing.

One can expand Gawande's point and observe that cultural values and reward mechanisms have a large impact on outcomes.  Within reason, the more adults emotionally engaged in the rearing of a child, the better.  The worst case scenario is the single parent with a young child.

In contrast is the child with two parents and perhaps involvement from four grandparents.  There are six sources of knowledge and experience (as many as fourteen if one were to include great-grandparents).  The one child is unique but among the six adults possibly involved in his or her upbringing there is a far greater probability of matching adult experience and knowledge to the actual needs of the individual child.  The chances of an optimized upbringing are dramatically higher than in the case of the solitary single-parent household.

You play this out across a whole population and the probabilities of child success are huge in the second scenario and small in the first.

There would be substantial differential impact owing to cultural attributes towards life success without any bigotry or discrimination.  A fact unacknowledged currently.