Above is the Ngram result for paradigm shift, a ubiquitous descriptive concept which can be quite slippery when applied to contemporary science. For example, every few years there is always a new “revolution” which is going to overturn “Darwinism.” Be it punctuated equilibrium, symbiogenesis, or epigenetics. But over time revolutionary fervor abates, and the orthodoxy remains standing, albeit with modifications and alterations, making it all the more robust.
I thought of this when I saw Andrea Cantor’s comment below in relation to twin studies:
Twin studies underestimate heritability only if you subscribe to the crude notion that the effect of genes is additive, i.e., keeping “environments” the same, the more similar two people are genetically the more alike they will be. This ignores everything we now know about the way genes work.
Genes are not self-activating: they do not turn themselves on and produce traits. Genes do not, in fact, produce anything. Genes are turned on and off by the epigenome in response to environmental inputs. If you are inclined to doubt this, then consider: If all the cells in our body are supposed to contain identical DNA, how do you account for the existence of different tissues and cells types (answer: the epigenome). Twins have been shown to have significantly different epigenomes in the womb. Does this show that twin studies underestimate heritability? Of course not. It shows, rather, that these studies are out of touch with advances in molecular genetics.
You are all committed to a crude, 19th century conception of the relationship between genotype and phenotype. Twin studies are based upon a scientific paradigm that has remained unchanged since the time of Galton. Problem is, recent advances in molecular genetics are bringing about a paradigm shift in the science of genetics.
Twin studies make it seem all so easy: All you need is a large data set that has zygosity status and statistical software and any undergraduate can unravel the biomolecular basis of human behavior.
Would that it were so easy.
I’m still scratching my head over the rather atrocious Brian Palmer piece in Slate, Double Inanity: Twin studies are pretty much useless. It’s of a quality which would make it appropriate for WorldNetDaily. Here are the responses of Jason Collins, Daniel MacArthur, and Alex Tabarrok. The comments at Slate were rather scathing too. I observed over at Genomes Unzipped that many of the assertions in the piece were in the “not even wrong/what does that even mean?” class. Palmer is apparently a freelancer at Slate, and they’re doing a bunch of stories on twins this week. I wonder if they just sent him the assignment with instructions on the slant, and he took it a little too far. Even if it was a polemic it was a shoddy and embarrassing one. My main concern is that many people perceive Slate to be an organ which publishes “smart” and well researched pieces, and they’ll take Palmer’s screed at face value.
The scientific problems with the article are legion. But still: how does something like this get published in a relatively high-end publication? Brian Palmer has editors presumably. If the copy was an undergraduate paper the prose would be relatively polished, but the overall structure of the argument and the naked guilt by association are marks of hurried sloppiness. The attempt to smear twin studies by association with Francis Galton was pathetic and childish. What next, turn against the concept of statistical correlation because Galton introduced it? There has to be more to this story than what we know. Or perhaps the people at Slate just don’t know anything about science.
A few friends have pinged me on this piece in Slate, Double Inanity: Twin studies are pretty much useless. The headline is bold, but the piece is just a sloppy mishmash. It’s really something amenable for a major “fisking,” but I generally don’t like doing that sort of thing, because it doesn’t seem a optimal allocation of time (though I have to note that the author seems to be implicitly using a colloquial form of the concept of heritability, which I think is going to confuse an already naive audience). A lot of the article is taken up with criticisms of political scientist John Alford’s behavior genetic findings on the heritability of ideology. I’ve had personal communication with other researchers in this area who actually are broadly critical of Alford’s methodology, but they’re still strongly invested in using genomics and behavior genetics to explore this issue. In other words, rejecting Alford’s conclusions does not entail that you just reject twin studies, as such.