Group Level Natural Selection

There has been much academic debate between evolutionary biologists, such as John Maynard Smith, W. D. Hamilton, George C. Williams, and Richard Dawkins, who advocate individual level selection plus rare cases of kin selection, and others, such as David Sloan Wilson, Elliott Sober and E.O. Wilson, who advocate multi-level selection. However, a consensus is beginning to emerge that a process of natural selection occurs at each biological level, i.e.: the genome, cell, organism, family, group, species, and ecosystem. Due to emergent properties, i.e., properties held by systems which are not held by their component parts, the process of natural selection at each level can differ. However, the process at each level tends to be undermined by stronger selection processes at lower levels.

E.O. Wilson described multi-level selection using the analogy of Russian dolls. The various biological levels can be likened to nested containers for competing genes. To varying degrees, the genes rely on each container for their survival and propagation. Thus, higher level selection can be a significant factor in some species and has probably played a part in human evolution.

Selection at cell level does occur within an organism. For example, recent research has shown that, in certain circumstances, cancer cells can evolve from healthy cells under pressure from the organism’s immune system. However, this form of evolution is normally a dead end. The cells act together to form the organism which is a container that they rely on for their continued existence. There may be billions of cells acting together over thousands of cell generations. However, evolution has shaped their genome to behave altruistically and, ultimately, the vast majority die out with the organism. Typically, only two or three carry the organism’s genes forward through reproduction. Thus, natural selection operates at the level of the organism rather than at the level of the cell.

Group selection forms part of the theory of multi-level selection. It is a natural selection process whereby traits evolve due to the fitness of a group of organisms, who are not necessarily kin, to their environment. The theory of group level natural selection proposes that groups which co-operate are more likely to be successful than those which do not. An individual will see it as beneficial to its own survival and ability to reproduce if it supports the group through co-operation. The concept has a long history. Darwin wrote on how groups can, but do not necessarily, evolve into adaptive units. This view was generally accepted until the mid-1960s. It was then criticised in favour of the view that evolution was based solely on the fitness of the individual. However, with advances in the science of multi-level selection, it is now returning to acceptability.

Both kin selection and group selection have, in a complex and inter-related way, had a part to play in governing human evolution. Kin selection has had a stronger influence on us than group selection. We will, for example, tend to favour a brother over an unrelated colleague. However, it is not the only factor which has determined our social behaviour. Charles Goodnight, in comparing the two, concludes that kin selection and multi-level selection should be considered complementary approaches which, when used together, give a clearer picture of our evolution than either can alone.

Together, kin and group selection explain some of the moral dilemmas that we face and how we handle them. There is often a conflict between the immediate interest of the individual, those of the individual’s kin, and the interests of the individual and its kin via the group. These interests, all of which are inherited, manifest themselves both in the form of competition between members of a group, and in the form of competition between groups. The individual must balance individual level competition and group level co-operation in a way which optimises their survival and the propagation of their genes. The way that we do so is explained by Freud’s model of the human psyche, i.e., the id, which is concerned with immediate personal interest, the super-ego which is concerned with group interest, and the ego which moderates between the two. However, because group selection is relatively recent, the super-ego is probably an inherited pre-disposition whose detailed contents are acquired through social learning. Freud’s model is relatively universal in human beings and is probably an innate consequence of multi-level selection, therefore.

Politics provides another example which demonstrates the existence of multi-level selection in humanity. The ideology of right-wing parties is one of individualism whilst that of left-wing parties is one of collectivism. Thus, we have the same dilemma in our political institutions both at a national level and at international level. Multi-level selection pervades humanity, therefore, from our individual psyche to our highest institutions.

In my next post I will give further examples of the influence of kin and group level natural selection on humanity.