Thinking on group selection
4 de April 2017
Darwin introduced the idea that selection might not only affect individuals but also other levels. This was a logical extension of his theory.
Genocentric Neo-Darwinism excluded group selection and found with Hamilton a model that helped to understand social insects on the basis of genetic relationships (kin selection). Subsequently, the topic of selection at group and other levels (holobiont, community, ecosystem) has been recosidered.
A recently published paper (Falgueras-Cano J., Carretero-Díaz J.M., Moya A. (2017). Weighed fitness theory: an approach to symbiotic communities. Env. Microb. Reports 9 (1): 44-46) proposes an interesting model based in Hamilton’s model for kinship selection and Wilson and Wilson’s model for group selection. The model presumes that individual fitness has two components, one that contributes to the fitness of the individual itself and another that contributes to the fitness of the group, and also that there is a selection pressure at the individual level and another that acts the group level.
Briefly, when the selective pressure is higher at the level of the individuals, they respond with a selfish behavior, whereas when the pressure is higher at the group level altruism is favored. Each altruist increases the fitness of the other members of the group and its own fitness is increased by the altruism of the other group members. But if the pressure on the individual is greater than on the group the selfish individual will be benefited by the other’s altruism. The model helps to understand cooperation without introducing kin relations and is a solid advance for the theory of multi-level selection. The authors also address the issue of symbiosis. In an environment that remains unchanged, the adaptations become more rigid and the symbiosis is fixed.
In animal societies, including ours, there are more complex situations. In humans, the behavior is not fixed as in a colony of eusocial insects. As in many other animal societies, selfish and altruistic behaviors coexist. Individuals compete for resources, but there is also competition between groups and, the more cohesive the group, the better it competes. Cohesion depends on the links between individuals —family relationships and affections, common origins (birth, education, neighborhood, etc.), race, language or dialect, religious or political beliefs, employment relationships, sports, hobbies, network communication, etc.—. Among pairs of individuals, links can be positive or negative.
When the network of links between the individuals of a group is considered, the cohesion of the group will increase with the proportion of positive links. Social groups, whether functioning on a democratic or dictatorial basis (they may be sects or mafias), build cohesive structures throughout their history (traditions, legal codes, language, beliefs, punishment of “unsupportive” individuals with social exclusion or even with the physical elimination of “traitors”…) in order to increase cohesion. Institutions such as the school, church, or army are also employed.
These cohesion structures are emerging phenomena. They are not in genes or individuals, but are transmitted culturally between generations. Individuals may feel as being more or less integrated in the “culture” of the group and their behavior can range from estrangement and “betrayal” to sacrifice in their defense. Individuals, driven by their personal interests, try to introduce mechanisms of forced cohesion into groups (trying to present their interests as collective). At the other extreme, some societies have relied on the abolition of individual interests and rights.
Large societies always contain distinct groups. Migration leads to the formation of societies in which very diverse groups of individuals coexist, each with its own cohesive structures. The survival of the characteristics of a group in these conditions depends on their position in relation to other coexisting groups, historical accidents or the strength of cohesion structures. This explains why the greater strength of Rome’s cohesion structures allowed the cultural assimilation of barbarians who had wined the war or that Jews or Gypsies had maintained their identity in many different countries over the centuries.
It is always dangerous to transfer models from one science to another and Falgueras-Cano et al. do not do it. However, his model is suggestive. In a human society, individuals compete for resources with their properties (health, social status, training, initiative, greediness, lack of scruples, etc.) and their success is measured by the position they reach within the hierarchical social network (money, power, prestige, children); we can not reduce all this to genetic selection, but there is a competitive pressure acting on the individual level. A society dominated by individual greed would lead to the tragedy of the commons (I keep it because, if not, another will do), where individualism leads to the exhaustion of the resource.
At the group level, fitness includes the degree of cohesion, which sociologists have tried to measure from several sets of indicators. It is not unthinkable that models can be build from sets of indicators synthesized in an index of individual capacities, one of social cohesion, one of pressure on individuals (largely determined by economic conditions) and one of pressure on groups (linked to relations “alliance-conflict” with the constellation of groups that surround them and to the accessibility of resources).
The interest of a model of this type would be to understand the processes of change in social cohesion and its consequences, a subject today of maximum interest. We are already witnessing the first stupid attempts to strengthen cohesion by putting barriers to population movements, expelling immigrants or eliminating individuals on the basis of ethnic or religious reasons, and exalting nationalisms of all kinds. A better solution would be to strengthen cohesion structures based on new parameters, solidarity and tolerance rather than “purity” (ethnic, religious or whatever), and to regulate greed at moderate levels, controlling the current trend towards the increase of the inequality that would lead to the collapse of the system.
In human nature there are as much trends to individualism as empathic responses to the problems of others. We must learn from Nature not only the struggle to survive against the others, but also cooperation, mutualism, and symbiosis. Kropotkin has explained this, and now it is more urgent than ever. But without falling into the dangerous idealism of ignoring that the individualism, equally natural in us, is a source of initiative and creativity. On these topics, I recommend the book by Frans de Waal The Age of Empathy. Nature lessons for a kinder society, 2009