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May 29, 2004
I mentioned that there is new evidence for the occasional inheritance of paternal mitochondrial DNA (mtDNA).
I have now seen the original research report. by Y Kraytsberg et al, in Science, vol 304, 14 May 2004, p. 981.
The results look pretty robust. Unlike earlier claims of paternal inheritance, which rested on statistical studies of populations, this one is based on sequence data from an individual with an inherited muscle disorder. Comparing mtDNA from the patient, his father and mother, shows not only paternal inheritance but recombination of mtDNA from both parents. Unless the authors have made a remarkable blunder, there seems to be at least one case of paternal mtDNA inheritance and (slightly more doubtful) recombination of the mitochondrial genome.
How important this is for studies of ancestry remains to be seen. One might think that if it were a common phenomenon there would have been clearer evidence before now.
May 28, 2004
Was Cos right?
Most folks have probably now heard of the brouhaha Bill Cosby has started via his remarks at the NAACP's shindig celebrating the golden anniversary of the Brown vs. Board of Education decision.
For those who have not, here is the gist of his comments summed up in one quote:
Ladies and gentlemen, the lower economic people are not holding up their end in this deal. These people are not parenting. They are buying things for kids – $500 sneakers for what? And won't spend $200 for "Hooked on Phonics."
My question is, was Cos right? Are the parents to blame or praise for their children's outcomes?
I postulate the answer is both yes and no.
Yes, in that biological parents give their children part of their DNA, which, ipso facto, means that they are "responsible" for their children's behavior. But a mom and dad cannot select what nucleotide sequences they give their children, so it is basically a pseudo-random crap shoot what predispositions the children will inherit. Unless a mom/dad specifically picks a reproduction partner based on the probabilities of what the partner will pass on to the offspring (which, I would say, is not a conscious action in most parents), the parents really do not volitionally act here. But this is not what most people would think of when talking of parents and their children's behaviors.
What most people think of when "parental effects" is the topic of discussion is the home environment the parents provide, including the child behaviors the parents reinforce and punish. But are these parental effects really that strong? Well, it depends on the behavior, but for the most part the answer is no. Judith Rich Harris has a theory, Group Socialization Theory, which postulates that, sans a few isolated constructs, it is a child's genes and peers that are the two major influencers of his/her life outcomes. The late David C. Rowe did a lot of work here before his untimely death, a lot of which supported Harris' view.
Personally, I think the literature supports a view that parents exert a lot of influence, but not in the conventional shared-environment (c^2) way. Rather, in addition to genetics, they influence their children by the environments they allow their children to find themselves, not necessarily the environments the parents themselves create. In other words, parents who pay for Smitty to go to science camp are placing him among a set of peers and role models that positively view math, science, and academics in general; so they are making it much more probable for Smitty to have a positive view of science, and make a career out of it. It is not that the parents are overtly cheerleading for Smitty to be a Chemist (as that is likely to have little long-lasting impact), but they are placing him in an environment where the norm is for chemistry to be highly valued.*
So, Cos is partially correct in that parents do play a part in their children's outcomes, but it is not as simple as saying parental behavior has a bijective relationship (much less a definitive cause-and-effect relationship) with child behavior. Rather, it is a more complicated relationship. Still, for what it is worth, I do have to say that I commend him for at least not giving lip service to some tiresome bromide about how society, TV, or some -ism is the plight of all wayward utes.
*Of course I realize that the ability to pay for science camp and/or the knowledge that such things exist, takes a level of intellect, etc., which, in and of itself, has an influence on Smitty's life outcomes.
May 27, 2004
There appears now to be good evidence that paternal mitochondrial DNA can occasionally be inherited. (See here.)
That's right: paternal mitochondria, from Dad's little wrigglers.
Sperms do contain mitochondria, but until now the usual doctrine (dogma?) has been that the egg always keeps them out, or kills them off if they manage to get in. (Though some, including the late John Maynard Smith, thought there was evidence to the contrary.)
It now seems that 'always' should be 'nearly always', and an occasional paternal mitochondrion gets through the egg's defences. This could have implications for evolutionary 'family trees' and divergence times. Estimates have hitherto been based on the assumption that all mitochondrial DNA comes down the maternal line.
How important this is presumably depends on how rare is the occurrence. If it's only one in a million, it may just be a minor curiosity, with no serious implications for evolution.
May 24, 2004
HIV & Iran
BioMednet Central has an interesting article about the attitudes and knowledge of Iranian students about AIDS.
Reflections on the "God Module"
When I was an undergraduate in college I stumbled upon an article on the "God Module." It was a very exciting moment for me because I was one of those individuals that just never "got" religion on an instinctive level. Tertullian's quip "I believe because it is absurd" struck me as one of the most peculiar (and absurd!) assertions one could make. The "God Module" seemed to offer an easy and concise answer: it was a matter of biology, destinity and nature. Of course, I accepted that environmental inputs were important, though I had always felt more thoroughgoing Skinnerian conceptions of religion and other complex behaviors "missed" something.
For the public, the idea of the "God Module" was easy to digest, and for the non-religious public, it became something that was part of the intellectual zeitgeist. A unitary cause explained why we were so different, why we dissented from the gods of our era, whatever era that might be. Though the scientists who offered the research initially were tentative in their findings, the public was quite easily swept up into inferring grand implications from a thin hypothesis so long as it tantalized their predilection for the One True Answer. Over the past few years I have become more skeptical of the "God Module," though I think that it is one important vector or principle component that contributes to the cluster of behaviors that indicate "religiosity."
First, I think it is important to compare the idea of the "God Module" to something that we are on more solid ground for, the "Language Module". Though one might decompose this construct into "lexical" and "grammatical" subcomponents, it clearly exists from the evidence of aphasiacs, and its biological reality seems confirmed by the crystallization of language acquisition capacity in one's adolescence.
But note that there are sharp differences between "language" and "religion," though both seem to be human cultural universals.
If there was a principle component that was the "God Module," I suspect religion would be much more like language. That is, it would not display such a large variation between individuals, a variation that one might even conceive of as a normal distribution (that is, most individuals are moderately religious, with minorities at either extremes). Rather, religion might be more like a polygenic trait, multiple components may intersect in an "additive" effect. A normal distribution is much more easily explained by multiple components contributing to religion, as very few individuals would have all components "off" or "on."
What could these "components" be? Well, I suspect they are the components of the modular mind, that is, religion emerges out of interactions between cognitive domains. For instance, the fear of death might be the result of our temporal sense, our ability to conceive of and visualize a supernatural agent emerges out of our visuo-spatial and general intelligence, our need to articulate and communicate is expressed through our language facility, while the rituals that solidify group bonds are expressions of social intelligence. I am of course greatly simplifying, but I think you understand what I am getting at.
This does not mean that the research into the "God Module" need stop (that is, neurotheology), I suspect it is an important component of "religiosity," and in some individuals, might be the dominant aspect. These might be mystics, prophets and assorted religious revolutionaries, who are the drivers of religious change in the social context. Therefore, understanding the "God Module" might allow us to understand why and how religious change occurs through the force of personality of a few individuals. But, to truly understand religious expression in times of stasis, we need to take a more broad view.
Of course, this applies in the universal context, it does little to explain the differences between religion. It is here that I think a deep understanding of social and historical forces is important. Various societies are buffeted and constrained in dissimilar fasions. For example, rational choice might be a good way to explain religious dynamics in the United States because the downsides of conversion are rather low as there is little social stigma attached to switching denominations. In contrast, social stigma is important in preventing conversions in Muslim countries, so a "rational choice" theory seems harder to model social dynamics.
Perhaps one might imagine all humans as a superspet. A large subset of this are the "religious." Within this subset, one could imagine other sets that define those impacted by rational choice considerations or those who are socially constrained, and the intersection between the sets where individuals must consider individual and group costs and benefits.
Ultimately religion is complex. Biology, psychology, sociology and history all play roles. Scholars will attempt to form paradigms from their own disciplinary angle, but it is important that they also admit that they are engaging in a first aproximation only, examining one component or scrutinizing one particular subset. Those who purport to have at their finger-tips the One True Theory seem only possessed of the hubris of gods.
Addendum: Let me elaborate on the importance of using a multi-component perspective: surveys of the Far East regularly show that individuals in that region tend to express a low belief in a personal God. But does that mean that they lead a ritual life less rich than say those of the Muslim Middle East? I suspect not. I do think one can make assertion that some populations are "less religious" than others, but it is almost certainly because there are differences in the expression of various modules or cognitive domains.
Out of here....
Just a personal note, I'm off to Bangladesh for family business for two weeks starting tomorrow, so I won't blog or be checking email after today. So if I'm ignoring your email, it's because I'm not reading it....
P.S. I've set the front page to 14 days instead of 7, if you are curious why things aren't going into the archives.
May 23, 2004
Pop vs. Soda
Interesting re-work of the Pop vs. Soda map.
Privileges of a child
I have heard this tripe before from Muslims in exactly these words more than once, so it must be written or promulgated somewhere prominent (to be sure, the anti-ERA movement in the 1970s also tried to push this message). For some women, an infantile position in society with no responsibilities as wards of men might be an optimal solution. Needless to say, this sort of mind-set isn't ideal for faciltating for the maintenance of a republic.
Cognitive perceptions of race
Here is a 3 year old article titled Perceptions of Race (PDF) by Cosmides, Tooby and Kurzban. A few caveats:
1) The authors do not seem to try very hard to eliminate normative judgements from their argument, which makes one a bit cautious about the reasons that they come to their conclusions (that is, is there a synthesis between ought and the logical & empirical?).
2) Tooby & co. have historically been more than happy to "triangulate" on the racial issue so as to inoculate themselves from charges of being politically incorrect (there is a mild recapitulation of the "race does not exist" mantra within the body of the article).
In any case, I am mildly convinced by the paper, because as the authors note, for most of humankind's history, other "races" were not part of our everyday experience. Therefore, it seems unlikely that specialized responses to other races were needed, or could have been selected for.
The authors reject the position that:
1) Racial perception is an outgrowth of the interaction between our visual and correlation-detection systems.
And are not convinced that (but do not dismiss out of hand):
2) Racial perception emerges from our conception of "kinds" (that is, categories of animals that are imbued with a specific essence, etc.).
Instead they put forward the hypothesis that racial perception emerges out of mental processes designed to detect coalitions and alliances. They offer some empirical evidence to support this position. One interesting anecdote to me that indicates that perception of race and coalitions are connected: I have had fair-skinned pale-eyed Arab American friends be judged as "non-white" in the presence of Italian or Greek Americans who were of a darker hue. I believe that Arabs, and in particular Muslims, are perceived to be in a different coalition, so when they are on the boundaries of American racial categories, they are put on the "other side," even if empirically there are "whites" who exhibit a range of phenotypes more at variance from "All American," in the cases I am thinking of, within eye-shot of the pale non-white in question.
The black khans
It is also found among many West Africans. This site asserts that it is common among East Indians.
A few points.
1) ~0.5% of the men in the world carry what is likely the Genghiside Y lineage (see here). This is the direct male line, that is, father to son, father to son, father son, and so forth. Asma Gull Hasan claims descent through the matrilineal line, so she wouldn't carry the marker (she doesn't have a Y chromsome and neither does her mother), but that doesn't mean she couldn't be descended from a daughter of a male who carried the marker, at some point in the past 1,000 years. Of course, that implies that it's not something to brag about, since many people through Eurasia could make as similar claim.
2) Limited data sets can skew perception. The term "Mongolian Blue Spot" is a misnomer if you look at the prevelance of the trait among Africans and other dark-skinned populations. This site asserts that the spot is more common among "dark skinned babies," though I suspect this impression comes from the fact that the writer is probably American, and most children with the Mongolian Blue Spot in the United States are probably black or Hispanic. In a similar fashion, a Masai warrior might assume that lactose tolerance is a Masai trait and that northern Europeans must have Masai ancestry since they have no problem consuming raw milk (or the reverse, and I believe recent research has implied that there were multiple mutations that allowed for metabolization of lactose in adults, implying no common ancestry).
3) Speaking of limited data sets, since Asma seems to imply she is a virgin, she probably shouldn't be talking a lot about the human body, since her exposure is probably limited to her own kin.
4) So that I'm an equal opportunity sneerer, KXB correctly notes that many Muslim South Asians tend to play up a tenuous exogenous origin when ~90% of their ancestry is "native" (I would have given a higher percentile figure, but I saw some recent data which suggested a higher frequency of West Asian lines among Muslims as compared to Hindus than what I expected. Also, note it was the Mughals who popularized many of the color terms in circulation in South Asia, as they, the "white Muslims," were keen on distinguishing themselves from the native "black Muslims"). But, many Hindus, especially high caste ones, tend to want to emphasize the fact that they are "Caucasians," just like Europeans, and there used to the bizarre practice of upper caste Hindus going to southern Sweden to see the land of their "Aryan ancestors." To see that this is a human universal, when Ambedkar, the "Dalit Saint," was asked if his people were descended from the indigenous pre-Aryan people of Maharashtra, he could only respond, "that is a hypothesis," as if this was a wild suggestion without any basis in fact (I also read that the Dalits of Uttar Pradesh were uncomfortable aligning with those of South India because they felt that they were somewhat superior on the Chain of Being). The winners are always our ancestors.