Tuesday, February 17, 2009

Bicameral Mind--Interview With Gregory Cohran

2Blowhards: Julian Jaynes -- thoughts? Reactions? And what about that "bicameral mind" idea?

Gregory Cochran: I read Jaynes' book years ago and thought at the time that he was deeply, entertainingly crazy. Nowadays, it seems likely that people have changed enough over recorded history to generate noticeable personality differences. That doesn't mean I buy his bicameral mind model: just the idea that people now may have significantly different minds from people then.

2B: One visitor thinks that "the best way to test Jaynes' ideas would be to study some of the uncontacted tribes in the Amazon and New Guinea and see if they are still of 'bicameral' mind." Has anyone bothered to do this?

GC: If someone really believed in bicameralism -- some non-Nebraskan -- sure. I wouldn't myself.

2B: From another reader: "[You say that people will cling to the Blank Slate myth as long as it pleases them to.] The Catholic Church reluctantly stopped believing in the geocentric model of the universe long before there were important practical applications. They had an enormous investment in the geocentric model, but the empirical evidence was too strong. Are you saying that the scientific evidence against the 'Blank Slate myth' will never be strong enough, or that the motivation to cling to the myth is stronger than that for the geocentric model, or perhaps that heresies are suppressed more efficiently nowadays?"

GC: I think people -- some people -- care a lot more about this than anyone ever cared about geocentrism. There are also practical political aspects.

2B: From another reader: "Depiction of trickster gods in West Africa seems a bit positive, at worst morally neutral. In Northern Europe, Loki was a clear-cut villain. Could that contrast come from selection-induced personality differences?"

GC: And yet Bugs Bunny is our hero. I think this line of analysis is about as sound and solid as Citibank.

2B: "I have heard that the wide varieties of thalassemia are the result of reproductive isolation. If populations mixed in Italy, the best ones would be common, and the rest rare. Maybe that was from Cavalli-Sforza? But maybe malarias varied regionally, leading to regional adaptation: there is no best resistance?"

GC: There are lots of places where several hemoglobin mutations (defenses against malaria) co-exist. Modeling suggests that in some cases some variants will eventually be replaced by others, but that process can take a long time -- in some cases far longer than falciparum malaria has existed. Falciparum malaria in Italy (at least in central and northern Italy) is less than 2000 years old: there probably hasn't been time enough for the dust to settle.

2B: "An androgen receptor allele associated with male pattern baldness shows signs of strong selection in some populations. Does the difference have cognitive effects, personality affects, does it increase paternal investment, reduce intergenerational mate competition, socially-mediated personality differences? I have an uh, personal interest in this one."

GC: I have no idea. There are some interesting regional variations in the average activity of the androgen receptor, but the variant linked to baldness is different. I hadn't heard that it looks selected: do you have a reference?

2B: "You say: 'brains have shrunk about 10% over the last 30,000 years, and almost certainly changed in other ways as well.' So, why is that? Is it that we have less need for more generalized brains? Or have genes that lead to more efficient brains predominated? Can we compare brain size between hunters and gatherers (such as are left) or slash and burn types with those who live in complex societies?"

GC: Nobody knows why the human brain has shrunk. It might be increased temperature. There is some indication that the cerebellum has become relatively bigger over this period: this might be a clue. Larger populations would tend to create more mutations, and some might have led to more efficient brains: certainly any change that preserved or improved function while shrinking the brain would be highly favored. As for brain size, Eskimos have larger-than-average brains (and score higher on IQ tests than other hunter-gatherers) while Australian aborigines, Pygmies, and Bushmen have smaller-than-average brains.

2B: "So it turns out that no one has really taken a hard look at interfertility among human population groups. I can't say I'm surprised. What about interbreeding success between dogs? Are there differences? Lions can breed with tigers, but Ligers are infertile, right? So much for the interspecies question. Where intra-species breeding success is at issue, I would assume -- perhaps mistakenly -- that the question would hinge on graduated differences rather than something like on/off. This is why I wonder if there is good data regarding relatively distant dog breeds, which aren't so different from human races."

GC: Female ligers are often fertile, in accordance with Haldane's rule.

As far as I know, all human mixes ever tried have been successful, but I don't think there has been much checking of the rate of miscarriages, measurement of average fertility, etc. There might be a problem or two.

There might also be hybrid vigor. Sometimes the offspring of two particular strains of a plant or animal species are sturdier, healthier, etc than their parents: two populations that have this property with respect to each other are said to "nick." For all we know, there are ethnic groups that have never had members intermarry but would produce really formidable offspring if they ever did.

Of course, the real point of that comment was to suggest an experimental program with, say, 100 ethnic groups, that involved systematically testing interfertility (i.e. making babies) in all 10,000 possible combinations: a vast mating matrix. I would say that we know the results of only one row of that matrix; the Irish and everybody else.

2B: "Of course the elephant in the bedroom is the huge gap between average black and average white IQ. Whites had to grapple with and survive ice age conditions. Blacks didn't. That's the the thinking as to why the gap exists." In other words, is the denial of the idea that substantial differences between population groups exist finally down to people wanting to avoid the black/white IQ difference?

GC: Nobody knows the historical/prehistorical causes of the gap. As for the motivation being a desire to avoid discussing or admitting black/white differences: partly, but there are other drivers, I think.

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Posted by Ajay :: 5:18 PM :: 0 comments

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