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Sure thing! I'll start with a disclaimer: this chapter was Fred Nijhout's baby. He has been thinking about these things for several years, and the models synthesize ideas from his larger body of work. https://twitter.com/drlynnchiu/status/1361733894962348036
Fred believes very strongly in the explanatory power of a systems approach. The goal of this project was to bring a more holistic perspective to bear on our familiar toy models of genetic assimilation and phenotypic plasticity.
For instance, when we talk about norms of reaction, we often depict them as tidy stepwise relationships between environments and phenotypes. They have a slope of 1, and two genotypes may be drawn as intersecting lines, depicting their different responses to common environments.
But Fred's work in developmental biology and insect physiology has shown him very few straight lines and many, many sigmoidal curves. So, a starting point for our chapter was this question: what happens to our toy model when we start playing with the shape of the lines?
From that place, Fred makes the really cool and creative move of turning two norms of reaction (depicting two sigmoidal curves, not straight lines) into a three-dimensional space. The sigmoidal curves intersect to form the ridges of a systems-level phenotypic landscape.
A goal of this paper is to offer a new heuristic--a new way of visualizing and talking about familiar concepts in developmental biology. It's a project largely about idealization, about abstraction, and that's where a philosopher can get their hands dirty.
The chapter developed through lots of discussion. Lots of frantic doodles on whiteboards. Fred even used a 3-D printer to make a tangible phenotypic landscape. We'd sit around it and point at ridges and valleys and talk about how these concepts literally mapped onto the object.
To that end, a philosopher can act as a kind of conceptual bookkeeper in these collaborations, ensuring that the paper doesn't unintentionally elide different usages of a concept. Thinking about why reaction norms evolve was a case where this kind of bookkeeping proved useful.
(For instance, the distinction between a loss of plasticity as the result of genetic assimilation versus a loss of plasticity as the result of selection *against plasticity* sans assimilation is an important one, and is often papered over in the literature.)
Being a philosopher in the biology is a lot of fun when you're working with scientists who appreciate the philosophy inherent to the biology. Fred is an exemplar of such a scientist. Gunter is another, of course, and his paper (helmed by @KzMckenna) is not to be missed.
