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Higher order thinking [Pharyngula]
The one thing you must read today is David Dobb’s Die, Selfish Gene, Die. It’s good to see genetic accommodation getting more attention, but I’m already seeing pushback from people who don’t quite get the concept, and think it’s some kind of Lamarckian heresy.
It’s maybe a bit much to ask that the gene-centric view of evolution die; it’s still useful. By comparison, for instance, it’s a bit like Mendel and modern genetics (I’ll avoid the overworked comparison of Newton and Einstein.) You need to understand simple Mendelian genetics — it gives you a foundation in the logic of inheritance, and teaches you a few basic rules. But once you start looking at real patterns of inheritance of most traits, you discover that it doesn’t work. Very few traits work as Mendel described, and one serious concern is that we tend to select for genes to study that behave in comprehensible ways.
And every geneticist knows this. Mendel was shown to have got some things wrong within a decade of his rediscovery: Mendel’s Law of Independent Assortment, for instance, simply does not hold for linked genes, and further, linkage turns out to hold important evolutionary implications. But I still teach about independent assortment in my genetics course. Why? Because you need to understand how to interpret deviations from the simple rules; it’s an “a-ha!” moment when you comprehend how Morgan and Sturtevant saw the significance of departures from Mendel’s laws.
Most of genetics seems to be about laying a foundation, and then breaking it to take a step beyond. Teaching it is a kind of torture, where you keep pushing the students to master some basic idea, and then once they’ve got it, you test them by showing them all the exceptions, and then announcing, “But hey! Here’s this cool explanation that tells you what you know is wrong, but there’s some really great and powerful ideas beyond that.”
That’s what’s fun about genetics: compounding a series of revelations until the students’ brains break, usually right around the end of the term. Over the years I’ve learned, too. Undergraduate genetics students usually collapse in defeat once I introduce epistatic interactions — the idea that the phenotype produced by an allele at one locus is dependent on the alleles present at other loci — but it’s always great to see the few students who fully grasp the idea and see how powerful it is (future developmental biologists identified!).
And that’s how I see the gene-centric view: absolutely essential. You must understand Mendel, and Fisher, and Wright, and Hamilton, and Williams, and once you’ve mastered that toolkit, you can start looking at the real world and seeing all the cases where it’s deficient, and develop new tools that let you see deeper. The new idea that Dobb’s describes, and that is actually fairly popular with many developmental biologists, is that phenotype comes first: that organisms are fairly plastic in response to the environment in ways that can’t be simplified to pure genetic determinism, and that the genes lag behind, acting to consolidate and make more robust adaptive responses.
I’ve written about genetic assimilation/accommodation before, and have given one lovely example of phenotypic change occurring faster than the generation of new mutants can explain. It’s always baffled me about the response to those ideas: most people resist, and try to reduce them to good old familiar genes. It’s a bit like watching students wrestle with epistatic modulation of gene expression when all they understand is Mendel, and rather than try to grasp a different way of looking at the problem, they instead invent clouds of simple Mendelian factors that bring in multi-step discrete variations. They can make the evidence fit the theory — just add more epicycles!
I’m seeing the same responses to Dobbs’ article — it’s still all just genes at the bottom of it, ain’t it? Oh, sure, but the interesting parts are the interactions, not the subunits. We need to take the next step and build tools to study networks of genes, rather than reducing everything to the genes themselves.
Source: http://scienceblogs.com/pharyngula/2013/12/03/higher-order-thinking/
