Original Publication: 03/05/2012
Edited for grammar/syntax: 07/24/2019
In this article, the researchers hypothesize that up until this date, all progress on kin selection theory has largely been abstract in nature and not provided any concrete evidence for the theory. They argue that, in order for kin selection theory to be fulfilled in an empirical system, several stringent conditions must be met.
First, all interactions that are measured must be “additive and pairwise”; that is, they must only affect the pair of individuals involved in the interaction. This means that synergistic effects, such as the simultaneous cooperation of more than two individuals, are unable to be measured or incorporated into any mathematical model of kin selection.
Second, they argue that kin selection theory can only be applied to a very limited subset of population structures due to the requirement of global updating of interactions wherein global updating is the idea that any two individuals are competing uniformly for reproduction regardless of their geographic proximity to each other.
Third, they argue that if these two requirements are met, and they can only be met in some limited, artificial world, then when these requirements are met that the organismal interactions within that aforementioned world are also acting according to the conditions of natural selection theory, and that kin selection theory does not provide any additional biological information.
Finally, the authors also argue that the apparent simplicity of kin selection theory compared to that of natural selection theory is an illusion. Since the primary component of kin selection theory is the calculation of inclusive fitness, and the calculation of inclusive fitness requires the state of “all individuals whose fitness is affected by an action, not only those whose payoff is changed.” to be known, then in effect kin selection theory is requiring the same information to be known as natural selection theory – the state of all individuals affected rather than only those whose payoff (fitness) is increased.
In order to overcome the limitations imposed by kin selection theory, the authors propose a general, multi-level model of natural selection theory using only the general principals of population genetics. This model is used to explain how eusociality might evolve in five distinct evolutionary stages.
First, an organism must reach a state where there are clear groups within a population. Groups typically form around resources, nest sites, when parents and offspring stay together, or when flocks go to known breeding grounds.
Second, these groups begin to accumulate traits, otherwise known as pre-adaptations, that will increase the overall cohesion and cooperation of these groups. One such pre-adaptation is when a parent places large numbers of paralyzed prey around her eggs so that when the eggs hatch they will have a food source readily available, and then she moves on to create another nest. The next step towards eusociality would be for the parent to stay near the nest and guard the eggs until they are hatched. However, at this stage, the offspring will still leave the nest, and so will the parent - there is still dispersion.
Third, the evolution of clearly eusocial alleles, that is, traits that enforce the primary traits of eusociality occurs. The key traits here are for individuals to stay in the nest instead of dispersing, and then other cooperative pre-adaptations can come into play.
The fourth stage is probably what can be called the optimization stage in which these eusocial alleles can be selected upon to reinforce the nest/colony structure.
The fifth is the final phase, and selection now operates on the colonies instead of the individual organisms, and the evolution of more derived traits such as castes (workers/soldiers), fungal farming, aphid farming, and other highly cooperative activities.
Here the authors have outlined the framework through which future studies can be conducted, most likely, which will be a combination of behavioral ecology and phylogenetics.
My criticisms of this paper can only be restricted to the authors’ use of the words “primitive” and “advanced,” which are common misnomers in evolutionary biology. A better term should be less derived or more derived, in reference to the ancestral state. For instance, the caste system of most ants is more derived compared to the loose grouping structure of some wasps (I am guessing!).
Nowak, M.A., Tarnita, C.E. and Wilson, E.O., 2010. The evolution of eusociality. Nature, 466(7310), p.1057. doi: https://doi.org/10.1038/nature09205