Self selection, other selection

Biologists like to classify selective events. Natural selection, artificial selection, sexual selection, kin selection, group selection and observation selection are all examples of selective categories. This post is about two more categories - self selection, and other selection. These are classification categories which mainly apply to individual decisions.

• Self selection involves decisions that affect the actor's own fitness. Positive self selection increases fitness, while negative self selection decreases it. Deciding to raise offspring is usually positive self selection. Deciding which of your shoelaces to tie first would not be self-selection - while it is a decision, it has negligible impact on fitness.

• Other selection involves decisions that affect the fitness of others. Mate selection is a well-known example of positive other selection. Selection of a rival for combat is a well-known example of negative other selection. However there are other examples of other selection which are not associated with sexual selection. Choosing a trade partner can increase others fitness of others. So can choosing who to groom, who to go hunting with or who to share food with. Nepotism counts as other selection, although it is also a type of kin selection.

Self selection and other selection are not intended to be mutually exclusive categories. Sexual species feature more other selection, as do more social species. I mentioned individual decisions above, but "individual" can be interpreted broadly to include all kinds of loosely defined groups that can be assigned fitnesses. Companies and families would be examples.

The terms can also be applied at the level of the gene. That's an interesting level because there, other selection is not "polluted" by cases of kin selection. However, it if often polluted by cases of linkage instead - genes can affect the fitness of other genes via linkage. The other selection is most useful when these "polluted" areas are not involved. I said that these forms of selection "mainly apply to individual decisions". What does it mean for a gene to "make a decision". It means it affects some behavioural outcome, relative to its alleles.

I've looked into the history of these terms a little. A common use of "self selection" is via self-selection bias. That usage doesn't seem very closely related because it makes no mention of fitness.