We are not the cause of ourselves
For one case the authors were able to measure for DNA and still they found that parenting styles affected the development of the children (p.104).
As for the effects of day care, it seems what matters for the mother-child relationship is the quantity of time spent by the mother taking care of the child, not the quality (p.166). For the intellectual development of the child, however, quality time matters not the quantity. By age four and a half, however, the children who spent more time in day care were more disobedient and aggressive. At least on average, those problems persist through the teen years. The good news is that quality of family environment growing up still matters more than day care.
This is from Tyler Cowen's summary of The Origins of You: How Childhood Shapes Later Life (published later this year). It's consistent with his ongoing argument against genetic-determinism.
Of course, no one denies that there are some results from the way we act with each other. But the predominant trend of the research is that genetics matter much more than we think.
Note the phrasing, 'At least on average, those problems persist through the teen years.' So it's not measurably different in adult life? That's consistent with the geneticist view that you can give your kids a certain sort of childhood, but you can't hot house a tulip into an orchid. Influence wears off.
If we take these results seriously, will people start advocating for more stay-at-home mothers and less day care? I doubt it. Does that not reflect the fact that we do not inherently believe we can make that much difference to the long-term outcomes of our children?
My argument isn't with people who think we can affect the way our lives work out, it's with the people who don't know that genetics set the parameters for the outcomes we are able to affect. Nurture is real, we just don't know how real.
This is the usual re-hash of determinism vs free will. Of course some sort of free will is available to us, but nothing like as much as advocates suggest.
It's like betting on a horse. You might be betting on a trainer and a stables and all that. But first of all, you're betting on heredity, innate qualities and so on.
I look forward to reading the book and understanding more about the Dunedin study.
It still seems likely that genetic variation explains more about who we are and the range of outcomes we experience than anything else, but I look forward to updating my view.
Hopefully, the long-term lesson we take from all of this work will be this one:
"All people are not created equal," Moffitt says. "Some have real gifts and talents, and some have real problems right out of the starting block. Once we accept that, we can't dodge the responsibility for social action."
Watching people's lives unfold over decades, she adds, "obliges compassion."
The causes don't change this much either way.