e. Group Level Natural Selection

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.

d. Kin Level Natural Selection Uncategorized

Kin Level Natural Selection

An early precursor to kin selection was the theory of inclusive fitness. This was proposed by J.B.S. Haldane in 1932 but developed and named by William Donald Hamilton in 1964. Hamilton’s theory is the basis of Richard Dawkins famous book, “The Selfish Gene” and argues that it is the survival and reproduction of genes, rather than organisms, that is the principal driver behind evolution. As a result, an organism can display altruism if this leads to a greater propagation of the genes it holds than would be the case if it acted solely out of personal self-interest. This relies on the individual organism being able to identify those genes in others. There are two main ways of doing so. Firstly, by knowing its kin or related family members and, secondly, by recognising external characteristics displayed by others with the relevant gene. However, there are several difficulties with the latter, for example whether the gene does in fact express itself in the form of recognisable traits and whether the organism can see those traits. Because such traits are often only skin deep, there is the potential for imposters to display them to benefit from altruistic behaviour.

The more specific theory of kin selection developed from Hamilton’s work. This theory states that an organism can behave in a way which maximises the propagation of its genes by behaving in an altruistic manner towards close relatives likely to hold the same genes.

Individuals in a species have approximately 99% of their genes in common. The remaining 1% constitutes their variable genome which accounts for physical variation within the species. The fitness of the 99% is well established and, thus, only genes in the variable genome, including any mutations, compete to propagate themselves. 50% of the variable genome is inherited from each parent. On average, therefore, an individual will share 50% with each parent, child, and sibling and, on average, 25% with each grandparent, uncle, aunt, nephew, niece, or grandchild. The theory of kin selection proposes, therefore, that it is advantageous in terms of the propagation of the variable genome to favour the survival and reproduction of three siblings over that of the self. Thus, genetically driven behaviour which facilitates this will propagate within the species.

Kin selection behaviour relies on the ability of an individual to recognise its kin. Nurture kinship, i.e., having raised, been raised by, or having been raised with another nuclear family member, is clearly an important factor, and can be observed in other species. However, the recognition of more remotely related kin, e.g., aunts, uncles, and other members of the extended family, requires considerable cognitive skill and, so, is probably limited to the more intelligent species.

As individuals become more remotely related, it only becomes possible to recognise kinship through physical appearance and, in the case of humans, cues such as language, dress, beliefs, etc. Thus, kin selection suggests that an individual is more likely to behave altruistically towards others of similar appearance and culture because these factors also suggest a similar variable genome.

Intuitively, kin selection operates within humanity. There is also a great deal of objective evidence for its presence. For example, research has shown that non-reciprocal help is far more likely to occur in kin relationships than non-kin relationships. It has also been shown that, when wills are written, there is a close correlation between kinship and the proportion of wealth passed on.

A small number of species can be described as eusocial. These species co-operatively rear their young across multiple generations. They also divide labour through the surrender, by some members, of all or part of their personal reproductive success to increase the reproductive success of others. In this way they benefit the overall reproductive success of the group. Eusociality arose late in the history of life and is extremely rare. Only nineteen species are known to display this characteristic: two species of mole rat, some species of brine shrimp, insects such as wasps, bees, and ants and, of course, mankind. In eusocial species, group level natural selection takes place due to competition between groups. In the case of the eusocial insects, the group is the nest or hive. Individual workers will lose their lives in the interest of the hive as a whole. It can be argued that this form of behaviour in insects is entirely altruistic and an inherited form of kin selection. However, in the case of humanity, this argument does not hold true because human groups display both kin altruism and non-kin co-operation.

However, there remain doubts whether individual and kin selection fully explain natural selection and human social behaviour since natural selection may also occur at higher biological levels. This will be explored further in subsequent posts.