The main piece of sad news this week is that I am just simply overwhelmed, and I am going to have to take a hiatus from writing. I will try to post occasionally, but look for once or twice a month rather than weekly. The reason is that I signed a book contract. I need to get writing on that, but before I do I have a chapter to complete, and I need to keep my research going – we are off to collect Flies in Southern Brazil next week. In some sense, it is good that I am slowing down. The logical progression of the blog would start to lead me into unpublished territory. The phenotypic approach has a lot to say about the evolution of sex, and the origin of life, for example. I think it makes sense to keep these a bit under my hat until they can get out in a citable peer reviewed format. The reason it is perhaps not so good is that there are a lot of ideas tearing at me that really do belong in the blog. Some subjects I should write about: It dawned on me that there is a difference between the contextual traits of contextual analysis on the one hand and indirect genetic effects on the other; I am once again confronted with philosophers of science talking about “group selection 1” and “group selection 2”, which are terms that I think confuse the issue and interfere with a nuanced understanding of multilevel selection. These are just issues that came up in the last week. Thus, I am not ready to abandon the blog yet, but I do think I need to slow down.
The book contract mentioned above is to write a book on exactly the topic of the blog, and as a result hopefully put it in a more permanent and citable form. The target date for a draft is a year from January, so it will be occupying a lot of my time for the next year.
So to rather randomly choose one of these topics. Lets talk about group selection 1 and group selection 2. This concept was introduced by Heisler and Damuth (1987, Am Nat 130:582), and recently popularized by Okasha (2006) (http://www.amazon.com/Evolution-Levels-Selection-Samir-Okasha/dp/0199556717/). The basic idea is that when you have individuals, or particles, you can do a multilevel analysis of selection on particles and selection on the collective, or you can just do an analysis of collective. Group selection 1 is an analysis in which fitness is measured at the particle level, and contextual effects of higher levels of organization are included. In other words, group selection 1 is what we think of when we think of group and individual selection acting simultaneously. In contrast, in group selection 2 we ignore the particles and focus on the collective. Thus, we might look at the fitness of bacterial colonies even though we know full well that these colonies are made up of individual cells.
This concept has gotten good traction in the philosophy world, and I will agree that it raises an important point. That is, it makes clear that results change depending on your point of reference. In the past there has been a lot of useless ink wasted when people were arguing about things like whether species selection was just the summed effects of individual selection, when in fact, they might be the same thing. That is, from a group selection 1 perspective in which the individual organisms are included in the analysis, it could indeed be that species selection is just the cumulative effects of selection on individuals. Even if this is true, however, if we take a group selection 2 perspective then indeed it is species selection, since we are only looking at the collective, or species.
So, this all sounds very positive, so what’s the problem? The problem is that every system is always group selection 1 and group selection 2 at the same time. Cells are made up of subcellular components, organisms are made of cells, groups are made of organisms. The levels need not be strictly hierarchical. For example, I “belong” to a number of different groups: My family, my department, the Evolution society, the blogosphere. These groups are in no sense hierarchical, and yet the do overlap to some extent. The group selection 1/2 perspective implies that there are really only two such levels, and basically enforces a false dichotomy. Question: are you working on particles or collectives? Answer: Yes.
So, rather than be destructionist I would like to offer a much better alternative. Let us clearly identify the level at which we assign fitness. This is Okasha’s particle, and my individual. Let me repeat that: The level at which we assign fitness is the individual. Then, rather than having the ambiguities of what exactly the levels are when we talk about group selection 1 and 2, we can instead clearly say that in this study the individual is the cell, whereas in that study the individual is the organism. The conclusions will, of course be different, but we don’t have to argue about them. We will know why they are different. They are different because they have different perspectives, they assign fitness at different levels.
Again, I apologize for taking a hiatus on my blogging. Hopefully I will be able to put up posts at a lower rate, and still keep this blog alive. One reason I will not be blogging next week is that we are going fly collecting. This will be an adventure, so don’t feel sorry for me!
We will be driving south into wine country to sample Tephritid flies. There are a number of interesting species complexes here. Hopefully we will be able collect some of interesting species.