A bit about explanatory models

In online settings, the most common explanatory model for talking about horse color is the base-plus-modifier concept. There are others that are also useful.



Five years ago I wrote a post that would come to be the most controversial to appear on the blog. At the time, reaction to “Bay is not a modifier” caught me by surprise. I wrote the post because I was convinced that the idea that bay was a modified form of black – an alternate way to explain the role of Agouti that had started to appear – was not helpful.


The existing framework of base colors and modifiers is an explanatory model. I have used variations of it in presentations for years, starting with my first one in 2001. To my everlasting shame, yes, that is Comic Sans you see on the slides below. The font was a bad decision, but the explanatory model proved to be a very effective approach for audiences who are visual learners, which is what most artists are.



It was just supposed to be a way to talk about the science, but it had come to be “the science” in the eyes of some people. It is not unusual to outgrow the usefulness of an explanatory model in science- think of the iconic image of the atom, which no longer precisely fits what is known about particles. What I learned from my experience with that post was that there were strong feelings about the existing model. Transitioning to a different explanatory model was likely to generate a pretty negative reaction.


That has been on my mind as I prepared to launch this site. I know that my own thinking has evolved so that I view pigmentation as a biological process, rather than the more artistic conception of layers of color (and alterations to those). In the years that Equine Tapestry has been dormant, the growing complexity of almost every aspect of horse color has pushed me more completely into that way of thinking. I am still most comfortable assessing variations in phenotype; I have never stopped being an artist. However, I do feel that the genetic mechanisms involved make more sense when seen as part of a process, rather than as discrete traits. It is how the subject is discussed in current literature.


One of my professors explained this understanding of genes in a really helpful way. Imagine you have taken apart a radio and removed a transistor. After the radio is reassembled using the remaining parts, it emits a constant, ear-splitting screech. You would not look at this situation and conclude that you had just removed the radio’s screech-suppressor; you would assume that you had mucked up the inner workings of the radio enough that it no longer worked properly. Genes can be seen in much the same way. What appears to be a gene for a given trait – in our case, color or pattern – is in fact a change to some biological process. The rapidly expanding list of coat color variations in horses are much easier to understand from the standpoint of changes to the inner workings of the pigmentation process.


That said, I know that changing explanatory models can be disorienting, especially if the model has been mistaken for the science itself. I am also not saying that, as a model, talking about basic colors and modifiers is wrong. Even when an explanatory model becomes an oversimplification (that is what usually happens to them), they don’t necessarily stop being useful. The simplified model of the atom, for instance, is still used in some settings to introduce the concept of atomic structure. For what I want to do here on Equine Tapestry, there will be times I need an explanatory model suited to some of the more complex parts of horse color. By explaining that now, I hope that it will be seen for what it is: just a different way to talk about horse color.


But I promise not all the posts will send us off into the genetic weeds. Equine Tapestry also exists so I have an excuse to share some of the thousands of pictures of cool-colored horses that I have taken over the years – and ask you to let me share some of yours! That will be the focus of the rest of this week’s posts, as I try to squeeze in as much as I can before the start of the Spring semester.