Gene Expression

Via Dienekes, Differential parental investment in families with both adopted and genetic children:

Stepchildren are abused, neglected and murdered at higher rates than those who live with two genetically related parents. Daly and Wilson used kin selection theory to explain this finding and labeled the phenomenon “discriminative parental solicitude.” I examined discriminative parental solicitude in American households composed of both genetic and unrelated adopted children. In these families, kin selection predicts parents should favor their genetic children over adoptees. Rather than looking at cases of abuse, neglect, homicide and other antisocial behavior, I focused on the positive investments parents made in their children as well as the outcomes of each child. The results show that parents invested more in adopted children than in genetically related ones, especially in educational and personal areas. At the same time, adoptees experienced more negative outcomes. They were more likely to have been arrested, to have been on public assistance and to require treatment for drug, alcohol or mental health issues. They also completed fewer years of schooling and were more likely to divorce. In adoptive families, it appears that “the squeaky wheel gets the grease.” Parents invest more in adoptees not because they favor them, but because they are more likely than genetic children to need the help. I conclude that discriminative parental solicitude differs in adoptive and step households because adoptive families generally result from prolonged parenting effort, not mating effort like stepfamilies.

What’s going on?

In Western countries adoptive parents are screened. Many of them are of higher socioeconomic status, and they adopt children from the general population, with a likely skew toward lower socioeconomic status biological parents. The traits which determine your social status are a combination of environment and genes, the latter mediated through various personality dispositions and attributes. In fact there is plenty of data to show that shared parental environment has a marginal long term effect. This is not to say that there aren’t environmental inputs which matter, and which adoptive parents bring to the table, but their direct guiding is not the operative element. In The Nurture Assumption Judith Rich Harris puts forward the hypothesis that the unaccounted for environment are peer groups.

Does this mean that adoptive parents are in a futile race against genes? No. Genes express themselves in an environment, and that environment is to some extent within the power of a parent to control. That being said the biological parent confers upon the child more than simply superficial physical attributes, or deep aspects of physiology. Rather one’s character is partially heritable, and that character is a critical variable in long term life outcomes.

As for the title, it’s perhaps crassly reductive, and no doubt simplifies the experience of being a parent. At least for many people.

Comments

  1. #1 Mark
    April 9, 2009

    Thank you for posting this. The blank-slate presumption really does pervade the adoption community (I know of what I speak in this regard!) so that parents are left fumbling to explain why their adoptive children – obviously not all of them – turn out so differently from their biological children.

  2. #2 gcochran
    April 9, 2009

    “a likely skew toward lower socioeconomic status”

    Nowadays, the biological parents are also more likely than average to have mental illness, which is fairly heritable. In the past, when more parents died by disease or accident, adoptees came from a more typical population.

  3. #3 Thorfinn
    April 9, 2009

    This ties into the economic literature of how should parents invest in children of different abilities.

    A common theoretical finding is that parents should attempt to equalize the earnings of their kids by investing more in the less-able child (under various assumptions). Sometimes studies find the opposite result, but it’s interesting that the theoretical case actually holds up here.

    I don’t get why Harris divides “direct guiding” by parents separate from their choices of which neighborhood to live in, how many books to have, what peer group your kids associate with, etc. If you lump everything that parents do together, parents remain very important.

    I would be interested to see a similar study in, say, rural Kenya. I imagine that environmental factors would dominate there, and that genetic factors are increasingly important as more people attain a minimum standard of living.

  4. #4 as
    April 9, 2009

    Two adoption stories.

    (1) I read about Dan Savage, the gay sex columnist, and his partner adopting a kid. They went in for open adoption, so they know the mother.

    The biological mother isn’t a functional adult. I think she’s often homeless. I don’t think he knows who the father of the kid is.

    (2) A friend of a friend adopted a boy whose parents are in jail. The kid was trouble from day one. As a teenager, he ended up in jail.

    In both cases, the adoptive parents had complete knowledge about the kid’s background, and they adopted without any qualms. It’s very noble, but still! To have your kid end up in jail…

  5. #5 Brian Schmidt
    April 9, 2009

    I guess one question is how to control for parental investment during pregnancy in order to distinguish that from genetic effects. The environmental reasons that might lead a woman to give a child up for adoption could also affect pregnancy. Adoptee infants may not be blank slates, but what’s written includes their gestational environment, not just their genes.

  6. #6 Orion9
    April 9, 2009

    Thorfinn, Harris doesn’t separate direct guiding from the choice of neighborhood, number of books, etc., they’re all part of the shared environment, the shared environment that has little lasting effects… I don’t see how you are led to the conclusion that “parents remain very important”. The peer group that Harris proposes as important is part of the unique environment, and is not chosen by the parents.

    Good write-up Razib. The fact that parents invest more in adoptive children, but they still have worse outcomes in many areas is another big blow to the nurture assumption.

  7. #7 Thorfinn
    April 10, 2009

    Orion9, here’s what Harris says:

    Researchers studied two groups of African-American school-age boys. These children all came from the same kind of home: low-income, headed by single parents. But some homes were located in black, poverty-level neighborhoods, and others were in neighborhoods that were predominantly white and middle-class. The researchers found that the African-American boys living in poverty-level neighborhoods were highly aggressive, but that those living in middle-class neighborhoods were no more aggressive than their white,middle-class peers. In both cases, these children had adapted their behavior to the local norms.

    But parents choose where their kids live! So they implicitly choose with whom their children associate and so forth (or at least the set of choices). This is one reason why parents spend a lot of time choosing which school to send their kids to. Harris also adds:

    I agree that American behavioral geneticists might have underestimated the influence of “shared environment” (the environment that siblings raised in the same family have in common) – not because they’ve ignored means but because the adoptive homes these researchers looked at tended to come from a narrowed range: adoptive parents are generally middle- or upper-middle class.

  8. #8 Fia
    April 10, 2009

    Nice post, it is good to see that there are people that do take such things into account. I wonder whether the analyzes that are done ever use the approach that is used in behavioral ecology and cross-foster experiments. Using proper statistical tools to actually quantify genetic and environmental components. Because from what I’ve read now, the only thing that’s taken into account is the environmental component (the step parents), which of course skews the outcome.

  9. #9 Huxley
    April 10, 2009

    My father, who was a doctor who had some dealings with adoptions, claimed that it used to be that babies who were put up for adoption were from middle class girls who got caught with a unwanted pregnancy and were thus relatively normal, while these days the babies who are put up for adoption are from more dysfunctional situations with parents who are of lower intelligence or suffer from mental illness or drug addiction, and that this makes a difference in how the baby turns out.

  10. #10 Pen
    April 10, 2009

    I think it’s already established in other contexts that parents are not a particularly strong nurturing force – at least against the social environment as a whole.

    I believe research on the children of immigrants shows that they are generally inclined to reject their parents’ language and culture in favor of that of the wider environment – sometimes merely by neglecting it, but frequently by disparaging it. Parents don’t always take this lying down, but they seem powerless to do anything about it – short of moving to a society that reflects their language and culture, that is. And in this case, I suppose we can assume that there is no genetic predisposition towards a given language.

    In the case of behavioral norms, well, some aspects of society certainly facilitate and even reward negative behaviors, so I don’t see what chance children with predispositions might have, regardless of their parenting.

  11. #11 John Emerson
    April 10, 2009

    Suppose that children of functional, successful parents were adopted into disfunctional homes? Would nurture / lack of nurture make no difference then? There must be some natural experiments out there.

    Anecdatum: I know a woman who was adopted by a mother who became schizophrenic after, but does have a definite tendency to conspiracy-thinking of the militia / goldbug type. She had a rare birth surname and knew which city she was adopted from, and in that city’s phone book people with her surname tended to be professionals.

    Anecdatum 2: I also used to know a twin of American-Hindu descent whose parents divided the twins in the divorce. One was raised as a Hindu woman in an educated family (don’t know the province or the caste) and one was raised as an American.

    Perhaps too there were pairs of twins separated and raised on different continents among the many US-Korean adoptees.

    I haven’t read the anti-nurture book, but I’m suspicious of it for two reasons (in addition to my own ideological tendencies, natch.) First, it’s got an attention-getting title that hooks into a lot of issues for a lot of people, making me suspect pop psych and an aggressive editor with an eye toward merchandising, as though it were a diet or anti-diet book. Second, psychologists spend so much time systematically bracketing out “culture” and local particulars in order to find universals that I don’t trust them to identify local or cultural influences when they try to control for them.

    In the same way, parents don’t usually understand what good parenting is, and they often mechanically apply rules from other pop psych books with similar problems. In other words, a proof that rule-following application of the consensus doctrine on parenting doesn’t do much good doesn not prove that no parents are better than others and that better parents don’t get better results.

    What I’ve seen among parents is that many parents following psych-derived childraising doctines end up sending terribly mixed messages, or even lying, because the book they choose violates some of their own gut feelings about parenting, requiring them to fake it. Maybe the best parents have the best gut feelings and can, for example, mix acceptance, strictness, high expectations, and leniency about chickenshit stuff properly. (And beyond that, there isn’t only one good mix; there are a bunch of good mixes and a bunch of bad mixes. My understanding is that violent inconsistent discipline is the worst, though some kids come out OK even from that).

    This sounds Luddite and to a degree it is, but a lot of new science is getting away from laws and moving toward respecting historical particulars more. And in part I’m just saying that I doubt that Harris’s attempt to define “good parenting” was a successful one.

    On two variables I can see that her net is too coarse or maybe too fine. “Number of books in the home” might mean a book-reading family that talks about books, or a non-reading family that puts books on their shelves. “A good neighborhood” mostly just means median housing price and a few other objective variables, but it includes both thriving communities and communityless suburban hellholes.

  12. #12 John Emerson
    April 10, 2009

    CORRECTION: I know a woman who was adopted by a mother who became schizophrenic after *adopting her, and she’s a well-functioning person at a medium level of ability*, but does have a definite tendency to conspiracy-thinking of the militia / goldbug type.

    Computer ate a line.

  13. #13 Orion9
    April 10, 2009

    Ah, I see what you’re getting at Thorfinn. The narrow range of adoptive homes is indeed a problem for behavior genetic research. It’s hard to measure how “narrow” that range is though, because most of the things parents consider to have an influence on their children fall within a middle-class framework, like how much TV they watch, reading habits, church attendance, etc. There is quite a lot of variety even within the middle class. To me this suggests that even if the range of adoption was studies was expanded, the results for the shared environment would come out similar. Harris is talking about the effect of the shared peer group on African-American kids, but what happens to their levels of aggressiveness when the shared environment component shrinks towards adulthood? They may end up being quite similar to African-Americans raised in poor neighborhoods.

    I think we should stick to explaining the effect of the peer group as part of the unique environment that varies within families, not between them. It may well explain why siblings turn out to be so different from eachother. In contrast, the shared component of peer groups doesn’t look like a good candidate to explain adult personality differences, because the shared environment is nearly always found to be weak to begin with, and then fade towards adulthood.

    The unique environment may not be parents saving grace either though, because we don’t yet know how to separate it from environmental noise. Thomas Bouchard Jr. has that he believes the measured outcomes are essentially genes plus noise (e.g. random events, accidents), which leaves very little room for parental control. Sad, but perhaps true.

  14. #14 Isabel
    April 12, 2009

    This is interesting – I’ve often wondered if there are genetic signatures of class rank…anyone know of any specific research?

  15. #15 Big Bill
    April 12, 2009

    “What’s going on?” you ask.

    The adoptive parents both affirmatively and equally chose a particular child from a range of possible children and suffered through months if not years of qualification tests, home inspections, psychological exams, etc.

    The stepchildren, conversely, were not picked, they were baggage, typically unwanted, and (for the step-parent) a constant, ever-present embodiment of a previous lover.

    My wife made me get rid of two perfectly normal cats that I acquired with a previous girlfriend. After a respectable wait (six months) we then went out and jointly picked out a cat “for us”.

    I guess I don’t understand why this is so difficult to see.

  16. #16 toto
    April 13, 2009

    It’s hard to measure how “narrow” that range is though

    What’s the IQ range (mean+sd) of adoptive parents?

    Then compare it to that of the biological parents, and of the children themselves. That should give you an idea.

  17. #17 Orion9
    April 13, 2009

    Toto, thanks for the response, but I think the range of adoptive parent’s IQ will not necessarily be a good proxy of how much variation there is in the environmental component. Sure IQ is related to a lot of good parenting practices, but it probably doesn’t account for a lot of variation in the case where everyone is middle class or higher. A better measure would be to compare the percentage of extreme conditions in order to a get a handle on the range of different environments. For example, how many adoptive families live in neighborhoods with high crime rates, compared to families in general? Or how many have instances of abuse, neglect, etc. I believe some research has been done on this to show there is a restricted range in adoptive families. But the things is, sibling and twin studies show roughly the same behavior genetic outcomes, where range restriction is not as much a problem. As I said before, this leads me to believe that the shared environment component is simply not very important for most outcomes.

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