Wednesday, December 3, 2008

More on father absence

I used to believe in a direct causal link between father absence and early sexual maturity in girls. The reasoning was that a daughter’s sexual development is accelerated when her biological father is replaced by a strange male (such as a stepfather). At the time, I saw this finding as a way to counter the argument that sociobiology denies human plasticity. It also offered hope that we could remedy a large number of social problems by ensuring father presence. Now I can’t help wondering whether all of this distorted my sense of judgment … and that of others.

One of the best studies on this subject is by Surbey (1990), who used a large sample (1,247 daughters) and measured several possible confounding factors: family size, birth order, weight, height, Quetelet Index, and socio-economic status (SES). On none of these measures did the father-absent daughters (16% of the sample) significantly differ from the father-present daughters. Nonetheless, they matured 4-5 months earlier than those who lived with both parents continuously and 7 months earlier than those who had experienced only an absent mother.

That sounds convincing. Yet how well was SES really controlled? The subjects were apparently university students, so they would have shared the SES of their mothers. But what about the SES of their absent fathers? What do we know about them? Typically nothing. And does SES fully capture all of the factors that distinguish father-absent daughters from father-present ones? Could it be that these two groups differ somewhat in their physiological make-up and, perhaps, in their genetic background?

These doubts led Mendle et al. (2006) to control for genetic background by examining the daughters of twin mothers. It turned out that the daughters did not differ in age of menarche if one mother was still living with the biological father and the other was not. Moreover, when the mother’s age of menarche was controlled among unrelated daughters, age of menarche no longer differed between daughters living with stepfathers and those living with biological fathers.


The presence of a step-uncle was as strongly predictive of early menarche as presence of a stepfather. It does not seem necessary for a child to experience the direct environmental influence of a stepfather to exhibit an accelerated age of menarche—as long as she is genetically related to someone who does have a stepfather. In a pair of twin mothers of which only one raises her children with a stepfather, the offspring of both twins are equally likely to display early age of menarche. It therefore appears that some genetic or shared environmental confound accounts for the earlier association found in female children living with stepfathers.

Mendle et al. (2006) raised another point. The correlation between father-absence and early menarche may be an artefact of population substructure:


The wholly Caucasian population of our Australian sample may explain our failure to replicate the strong father-absence association observed in more ethnically diverse American samples. Given that African American and Latina girls experience menarche on average 6 months prior to Caucasians (Herman-Giddens et al., 1997), it may be that the previously established associations between early menarche and lack of a traditional two-parent family structure are affected by racial differences in family structure. Correlates of early menarche may additionally be complicated by effects of poverty or socioeconomic status. For example, Obeidallah, Brennan, Brooks-Gunn, Kindlon, and Earls (2000) obtained a difference in age of menarche between Caucasian and Latina girls, but this effect disappeared after controlling for socio-economic status.

Why didn’t other studies control for ethnicity? Apparently because the authors felt that SES controls were sufficient. This may be true for Hispanic Americans but it is not for African Americans. Even among Hispanics, there may still be substructure effects. It is known that Hispanic SES correlates with European ancestry, so controlling for SES would bias this population toward individuals who are more genetically similar to European Americans.

All of this makes me wonder about all of the data that supposedly prove the adverse effects of single motherhood. Undoubtedly, there are adverse effects. But there are probably many “pseudo-effects” that would persist even if the biological father could be forced to stay around.

For what it’s worth, I spent part of my pre-adult life in a father-absent family (my father died of a cerebral hemorrhage). Yes, there were adverse effects, poverty in particular. Nonetheless, I think I would have ended up being substantially the same kind of person even if my father had continued to live.

References

Mendle, J., Turkheimer, E., D’Onofrio, B.M., Lynch, S.K., Emery, R.E., Slutske, W.S., Martin, N.G. (2006). Family structure and age at menarche: a children-of-twins approach. Developmental Psychology, 42, 533-542.

Nettle, D. (2008). Why do some dads get more involved than others? Evidence from a large British cohort. Evolution and Human Behavior, 29, 416-423.

Surbey, M.K. (1990). Family composition, stress, and the timing of human menarche. In T.E. Ziegler & F.B. Bercovitch (eds.) Socioendocrinology of Primate Reproduction, pp. 11-32, New York: Wiley-Liss Inc.


8 comments:

Tod said...

Why has the age of puberty declined in recent decades? III "(Thanks to Jay Belsky, as usual, for pointing me to the latest scientific literature on this topic)"

Anonymous said...

Todd, in the reference you give, no mention is made of any ethnicity correction.
If there is no ethnicity correction, the study is politically correct (= more money and grants), but scientifically flawed.
Even if, as Peter said, I'd like to think that my presence with my daughter helps to keep her away from bad girl behavior. I might have been wrong after all, but who can we trust, scientists ?

You guys in the academic live in an ivory tower, or a glass castle, as you prefer. Not much work and lots of money IF you stay politically correct, that is.
I work in the american public school system and not in the worst area.
Believe me, in a public US school, it takes me 1 second to make an "ethnicity correction" to know if my day's gonna be about hell and yelling or about decent teaching. I could even say that my consumption of motrin is strongly related to that "ethnicity coorection".
So you guys better speak nicely to get your grants and pretend that an ethnic correction is unnecessary, yeah, we all know that.

RG

Tod said...

Satoshi Kanazawa is surprisingly free of political correctness.If the truth offends, it’s our job to offend He's aware of polygyny and mate quality considerations, and speculates on the implications of competition for females in polygynous societies. Possibly his own ethnicity works to give him more leeway, as when when he said this.
I was being a bit sarcastic with the quote, I think Peter Frost's post gives a far better explaination.

Tod said...

In remarking on a comment at a previous post Peter Frost said The European pattern of skin, hair, and eye color
"Imagine the following situation in ice-age Europe: one out of three women would never marry and have children; the other two would lose considerable reproductive time waiting to marry (or remarry, in the case of young widows). At Echoes of the Upper Paleolithic? ,
"Even in a small community, mating opportunities do come up, such as when a woman dies in childbirth".
Surely the expectation would not be that the European upper Paleolithic conditions would have brought about a later menarche.

What I am wondering is why
African American and Latina girls experience menarche on average 6 months prior to Caucasians (Herman-Giddens et al., 1997),
The earlier ice age Europeans became mature enough to be competitive against other females on the marriage market the better; however mature a female had to be to get married, earlier menarche means less time until that level of maturity is reached.

The longer their time on the market greater their chances of getting a scarce opportunity to marry. Therefor earlier menarche means a greater chance (over time) of getting married (all other things being equal). So the earlier the better.

Maybe there is a limit to how early but menarche significantly later than other populations seems to be an anomaly to me. (J. Philippe Rushton would have a ready answer I'm sure)

Peter Frost said...

I'm sure Philippe Rushton has an answer. He would say that children in non-tropical environments required a longer period of development and parental training in order to acquire the life skills they needed for survival and reproduction.

I don't really know myself. The later age of menarche in European populations may be a relatively recent evolutionary development that occurred in postglacial times, perhaps even during historic times. That sounds weird, but it wouldn't take very long to bring that kind of evolution about. And different cultural systems have had different attitudes to timing of reproduction and age of marriage.

Tod said...

Might the selection against early menarche be related to younger mothers not having accumulated enough of the special fat stores necessary for giving birth and breastfeeding a child and consequently having less viable children.

Alternativly the youngest mothers may have been too irresponsible to properly care for a baby in -25 degrees.

Anonymous said...

21 000 years old figurines found in siberia

http://www.cnn.com/2008/TECH/science/12/03/stoneage.art/index.html?iref=mpstoryview
they have the same look as the previous Venuses, kind of need of a liposuccion with some, I think, prognathism in this case. Definitively an african look.

About fatherhood, I continue to think that male hunters choose their mate to have the sort of kids they want, especially the male kids. I believe the neotenic traits were being selected but my intuition tells me that's it's not enough. There must be something else that gave a reason for a dad hunter to choose neotenic traits and it has to be some advantagous behavioral features. And maybe the late menarch and fair traits in females are just a side effect of the traits that were looking for in males.

I'm not a spychologist but the differences of behavior in a classroom between african american kids and white kids are striking. One of it is the ability to focus to perform a task that seem initially un-reachable, while african american kids will try to avoid the task if they think they can't do it. Even if african american kids have an obvious physical strength advantage over white kids, I am convinced that in a hunting or fight situation, they would not challenge an adversary that look bigger and stronger while the white kids could be persuaded to do it depite their relative weakness. Call that fearlessness or a higher threshold for fear but this kind of behavior would be extremely valued by hunters and maybe that trait passed along with other neotenic physical traits.

I have observed this fearlessness behavior, this kind of detachment from scarry situations, in people from nobility that are very abubdant in the military forces. The military is the natural niche for them. They abhore working, and they enjoy war, litteraly. One of my uncle has a so high treshold for fear that it is scarry. He fears nothing and shows no stress whatever the situation.
He is not specially smart beside that, but I can't help to think that this trait is genetic, he couldn't fake it or learn it. And maybe it's just a coincidence but in the famnily, he's the one with the most nordic look.

RG

Anonymous said...

For exemple I've seen my uncle going to pet a seemingly agressive big dog, hold in chains, that everybody was scared of. I'm sure my uncle never pet that dog before(it was not his) but he was just not scared. Despite the growling and the display of rage, he went straight to the dog and amazingly, the dog seing no fear in my uncle's eyes, accepted the petting and calm down. Another time my uncle went to pet a one ton bull just like it was a puppy. He is the kind of man who could surely tame a lion.
So here is the idea: a long time ago, maybe this fearlessness feature was passed amoong neotenic traits and was usefull to tame wolfs and wild horses.

RG