About a month ago I posted quite a bit about Neandertal introgression into modern humans. That is, the uptake of Neandertal alleles are a few specific adaptively salient loci even while ancestry remains predominantly African. Now John Hawks and Gregory Cochran have a new paper out, Dynamics of Adaptive Introgression from Archaic to Modern Humans, which synthesizes the first of the new results. The paper is open access, but I’ll throw out the money shot:
We suggest that adaptive introgression of alleles from archaic humans may be one of the central mechanisms leading to the “human revolution.” The behavioral characteristics
of modern humans, including the employment of symbolic culture and sophisticated technologies, followed the attainment of modern human anatomical features by a considerable delay (Klein and Edgar 2002). The notion that a single small population of incipient modern humans had the perfect genetic combination for ultimate success seems quite improbable. Instead, the long coevolution of modern anatomy and behavior in contact with archaic humans, even as those archaic populations appeared to diminish, provided a rich source of adaptations for the expanding modern population. With current genomic techniques, we are beginning to find these archaic genes. We expect that they will prove central to the story of modern human origins.
What Hawks and Cochran propose is that introgression of adaptive alleles into the Out-of-Africa substratum is the key to humanity as we understand it.
Here is a summary of findings by a paper which suggests that the vast majority of genetic counselors tend to err on the side of protecting a mother’s privacy if her husband is not the father of her child. Here is an important point though:
It is much more likely that bringing up the possibility prior to testing will put the woman in the very position we are trying to protect her from. … If, as I have suggested, the counselor plans to attempt to keep paternity but not personal genetic information from the man, it is probably better not the discuss the issue ahead of time.
The problem is pretty obvious, for autosomal recessive diseases like Cystic Fibrosis both parents need to be a carrier. There have been instances when “fathers” found out they weren’t carriers, and that is how they discovered that their child was not their biological offspring (this is not a non-trivial consideration when medical expenses can result in a great deal of debt and the biological father is absolved of any financial responsibility). But there is another angle which is important: a man who is ignorant of the ramifications of autosomal recessive diseases and the ease of paternity checking status is likely to be dull in the first place. Additionally, cross-cultural data tends to show that high socioeconomic status males are much more confident of the fidelity of their partners, and have reason to be, paternity misassignment for these males is as low as 1%.1 On the other hand, lower socioeconomic males tend to be cuckolded far more often. In the future relatively cheap and ubiquitous genetic screens will make one’s autosomal recessive status something that most individuals will be aware of, at least abstractly, but the less intelligent males are probably the ones who won’t do the punnett square.
Wondering how dull some low SES males can be? Watch the video below the fold….
Check out the ScienceBlogs group portrait. They caught me chillin’ with my buddy PZ. I wonder if the designer who worked on this ran out of brown pixel, cuz Selva & I look mighty pink! Chris Mooney out front looks a bit uncomfortable. And straight up, WTF are Evil Monkey & Mike Dunford doing???
Ali is talking about Andrew Sullivan using his “30 years War:Sunni vs. Shia, etc., in Iraq” analogy. All the talk is cool, but there’s a serious problem with the analogy: no one knows anything about the 30 Years War! You heard me right. For an anology to work like so: X ⇒ Y, you need to know a about X to map inferences onto Y, for the nature of Y is unfamiliar and X is familiar. The idea is that the 30 Years War will convey information to those not in the know about the current conflicts in the Middle East which emerge from sectarianism. But again, the problem is that hardly anyone knows enough about the 30 Years War to really map anything novel from it to the current events. Though straight up, who is our Wallenstein, because that was a hardcore thug!
P-eter comments on the Pakistani family which can’t feel pain. I remember in a genetics course once seeing the professor chart out a pedigree and calculate inbreeding coefficients and the expectation of the unmasking of deleterious alleles given certain matings. Now and then we would laugh nervously since of course real matings between individuals so closely related would be creepy and unethical…but Pakistan with its culture of cousin-loving down the generations1 makes the science possible in real life! Let a thousand deleterious recessives bloom across the landscape!
1 – Remember that inbreeding is particular problematic in a society where cousin-marriage is normative because the coefficient increases as you sum across recent common ancestors, and in such society cousins are likely to be related by many different paths.
Bryan Caplan reviews a survey which suggests that women are more religious cross-culturally than men. If you’ve been involved in the Freethought movement this won’t surprise you. Here’s an important point:
Once people admit that this gender gap exists, the most popular explanation is that women are “socialized” to be more religious. Stark and Miller put this theory to the test. If the socialization hypothesis is true, they reason, then the gender gap should be larger in more traditional societies where socialization pressure is more intense. Make sense to me.
Survey says: Dead wrong. In fact, the gender gap is smallest in the most traditional societies, and largest in the least traditional societies! In societies that approve of single motherhood, with a high abortion rate, low fertility, and high female labor force participation, the religiosity gap between women and men is especially large.
How to interpet this? Since I focus on genetics I think it is easy to conceptualize this as a norm of reaction, different environments result in different outcomes starting with the same biological material. In a traditional society it seems plausible that social constraints are strong. One can analogize this to the differential reaction of individuals to variation in resources (some individuals may respond more negatively toward deprivation, others more positively toward resource abundance). Genotypes which might react the same in environment x may respond very differently in environment y. My previous post on innate atheism is also applicable insofar as one ca view religiosity as threshold trait, and particular environments may simply result in saturation of religiousness (e.g., Saudi Arabia).
So what are the roots of male vs. female difference? I know the general paradigm used by researchers who presented the original results, they’re economically oriented rational choice types. I think a problem with this paradigm is that they too often view these issues rationally, as if minds are not bounded and biased by arational incoherences and illusions. These researchers operate from intuitions derived a priori instead of availing themselves of the psychological literature which draws upon empirical research which outlines how people really think. Caplan says something which I find interesting:
Men and women have different cognitive orientations – a difference that is in large part genetic. As the Myers-Briggs personality test powerfully confirms, men are more Thinking, and women are more Feeling. (Or if you prefer the Five Factor Model, men are less Agreeable).
On a deep level, then, men are more inclined to want some hard proof that religious claims are true, while women are more willing to take religious teachings on faith because they sound nice. Burn me at the stake if you must, but it’s true.
I think there is a serious problem here: Caplan seems to assume that religious beliefs emerge out of some social matrix and that women “take on faith” their truths. The cross-cultural similarities of cognitive representations of the divine point to another possibility: that religiosity emerges from natural human psychology, and in particular gods are simply agents which humans intuitively sense “must be there” because of their agency detection biases. So to male fvs. emale differences, why? I believe women have, on average, greater social intelligence and are likely to see more agency in the universe around us because of this. Men are not as religious less because of their innate skepticism, but because a greater proportion lack a powerful intuition of divine agency in the universe around us. There are other factors, but I suspect his is a large component. One might test this by studying males and females who are matched on the autism spectrum, I predict that most of the intersex difference in religiosity will disappear.
The virginity thread generated a lot of response. The virgin lot of the nerd, ah, so cliche. And yet now I’m having a really weird moment, I’m at the local wine bar and a very attractive hostess1 is recommending books in the science fiction genre to another (far less attractive) hostess. So far I’ve heard Ender’s Game, Hyperion and Snow Crash tossed off as appropriate for a “newbie.” Is this the Twlight Zone??? Am I a freak to think this is freaky? I haven’t had a sip of wine, so it isn’t the alcohol.
Update: She’s reading American Gods I notice (taking a break).
Update II: Smokin’ ScienceBlogger Shelley comments. For the record, the key issue for me was the intersection of science fiction && female physical hotitude.
Update III: On second thought, I think the Princess Bride era Robin Wright Penn is probably a better description of the “Hot Girl.” And another tidbit for those wanting to make this about science & women, I am to understand that this individual (I am a regular) is a history major.
1 – Think Reese Witherspoon’s more attractive brown-haired cousin.
Now, look at this quote:
…Geographic origin stories told by DNA can clash with long-held beliefs, threatening a world view some indigenous leaders see as vital to preserving their culture.
They argue that genetic ancestry information could also jeopardize land rights and other benefits that are based on the notion that their people have lived in a place since the beginning of time.
First, does this sound familiar? Science clashing with long-head beliefs? Second, why the hell are land rights and benefits contingent upon mythologies which can be empirically debunked?
The story of lactose tolerance evolving multiple times has blown up a bit, thanks to Nick Wade at The New York Times. Some people are making analogies to light skin evolving via different genetic architectures (remember, skin color is a polygenic trait, albeit dispersed over ~4 loci of large effect). But there is a difference, light skin color emerges via loss of functionality or expression on the loci which result in pigment production. There are many ways to lose function, but it generally is considered more difficult to gain function. And yet this is what lactose tolerance is. Or is it? Remember, infants and toddlers can digest lactose fine, the issue is that tolerance persists in some populations. In other words, whatever pathways shift so that metabolic shunts are closed which drive lactose breakdown, all you need to do is short circuit this abolishment of gene expression on the LCT locus. The data implies that in Europeans a cis-acting element continues to induce transcription from LCT in adults, but other data implies that African groups may have stumbled upon a strategy utilizing the epistatic interaction across loci via a trans-acting factor to retain function on this locus. Fundamentally this isn’t as if various human groups have evolved ways to breakdown something evolutionarily rare such as cellulose, rather, it is simply utilizing the standing genetic variation to tweak a mundane physiological process which is found across young mammals.
A SNP in the gene encoding lactase (LCT) (C/T-13910) is associated with the ability to digest milk as adults (lactase persistence) in Europeans, but the genetic basis of lactase persistence in Africans was previously unknown. We conducted a genotype-phenotype association study in 470 Tanzanians, Kenyans and Sudanese and identified three SNPs (G/C-14010, T/G-13915 and C/G-13907) that are associated with lactase persistence and that have derived alleles that significantly enhance transcription from the LCT promoter in vitro. These SNPs originated on different haplotype backgrounds from the European C/T-13910 SNP and from each other.
Mike Dunford points me to an organization that supports families who’ve lost loved ones in the Iraq War. From Mike:
As I mentioned recently, a number of soldiers in Iraq will be running the Honolulu Marathon this weekend. The course goes around a base several times, mostly over dirt roads. In part, running the Honolulu Marathon lets folks maintain a connection with home, but that’s not the only reason that they are running. They’re also running to support TAPS – an organization that provides support to the families of people who die while on active duty in the armed forces.
You can see the casualty counts yourself, nothing to sniff at.
Data from Sexual Experiences of Adolescents with Low Cognitive Abilities in the U.S.
What’s the reason for these results? I think one of the simple ones (though not the only one) might be a form of positive assortative mating: like with like. If you assume that affinity is proportional to cognitive similarity than the sample of individuals for someone who has an IQ of 100 vs. 130 or 70 is far higher for any given range. For example, nearly 2/3 of individuals on the frequency distribution lay within 1 standar deviation of someone with an IQ of 100. In contrast, only around 1/7 of the population is within 1 standard deviation of someone at 130 or 70.