Group selection

, such as the lekking of blackcock, spoke of "the good of the species". Blackcocks at the Lek watercolour and bodycolour by Archibald Thorburn, 1901.|alt=image of lekking blackcock, an instance of social behaviour Group selection is a proposed mechanism of evolution in which natural selection acts at the level of the group, instead of at the level of the individual or gene. Early authors such as V. C. Wynne-Edwards and Konrad Lorenz argued that the behaviour of animals could affect their survival and reproduction as groups, speaking for instance of actions for the good of the species. In the 1930s, Ronald Fisher and J. B. S. Haldane proposed the concept of kin selection, a form of biological altruism from the gene-centered view of evolution, arguing that animals should sacrifice for their relatives, and thereby implying that they should not sacrifice for non-relatives. From the mid-1960s, evolutionary biologists such as John Maynard Smith, W. D. Hamilton, George C. Williams, and Richard Dawkins argued that natural selection acts primarily at the level of the gene. They argued on the basis of mathematical models that individuals would not altruistically sacrifice fitness for the sake of a group unless it would ultimately increase the likelihood of an individual passing on their genes.…

, such as the lekking of blackcock, spoke of "the good of the species". Blackcocks at the Lek watercolour and bodycolour by Archibald Thorburn, 1901.|alt=image of lekking blackcock, an instance of social behaviour Group selection is a proposed mechanism of evolution in which natural selection acts at the level of the group, instead of at the level of the individual or gene. Early authors such as V. C. Wynne-Edwards and Konrad Lorenz argued that the behaviour of animals could affect their survival and reproduction as groups, speaking for instance of actions for the good of the species. In the 1930s, Ronald Fisher and J. B. S. Haldane proposed the concept of kin selection, a form of biological altruism from the gene-centered view of evolution, arguing that animals should sacrifice for their relatives, and thereby implying that they should not sacrifice for non-relatives. From the mid-1960s, evolutionary biologists such as John Maynard Smith, W. D. Hamilton, George C. Williams, and Richard Dawkins argued that natural selection acts primarily at the level of the gene. They argued on the basis of mathematical models that individuals would not altruistically sacrifice fitness for the sake of a group unless it would ultimately increase the likelihood of an individual passing on their genes. A consensus emerged that group selection did not occur, including in special situations such as the haplodiploid social insects like honeybees, where kin selection explains the behaviour of non-reproductives equally well, since the only way for them to reproduce their genes is via kin. In 1994 David Sloan Wilson and Elliott Sober argued for multi-level selection, including group selection, on the grounds that groups, like individuals, could compete. In 2010 three authors including E. O. Wilson, known for his work on social insects especially ants, again revisited the arguments for group selection. They argued that group selection can occur when competition between two or more groups, some containing altruistic individuals who act cooperatively together, is more important for survival than competition between individuals within each group. A large group of ethologists conceded that while inclusive fitness may be debatable, it was still a useful theory in practice. However, the vast majority of behavioural biologists have not been convinced by renewed attempts to revisit group selection as a plausible mechanism of evolution. ==Background== Charles Darwin developed the theory of evolution in his book, Origin of Species. Darwin also made the first suggestion of group selection in The Descent of Man that the evolution of groups could affect the survival of individuals. He wrote, "If one man in a tribe... invented a new snare or weapon, the tribe would increase in number, spread, and supplant other tribes. In a tribe thus rendered more numerous there would always be a rather better chance of the birth of other superior and inventive members." Once Darwinism had been accepted in the modern synthesis of the mid-twentieth century, animal behaviour was glibly explained with unsubstantiated hypotheses about survival value, which was largely taken for granted. The naturalist Konrad Lorenz had argued loosely in books like On Aggression (1966) that animal behaviour patterns were "for the good of the species", without actually studying survival value in the field. The evolutionary biologist Richard Dawkins wrote that Lorenz was a good of the species' man", so accustomed to group selection thinking that he did not realize his views "contravened orthodox Darwinian theory". The ethologist Niko Tinbergen praised Lorenz for his interest in the survival value of behaviour, and naturalists enjoyed Lorenz's writings for the same reason. In 1962, group selection was used as a popular explanation for adaptation by the zoologist V. C. Wynne-Edwards. In 1976, Dawkins wrote a well-known book on the importance of evolution at the level of the gene or the individual, The Selfish Gene. From the mid-1960s, evolutionary biologists argued that natural selection acted primarily at the level of the individual. In 1964, John Maynard Smith, C. M. Perrins (1964), and George C. Williams in his 1966 book Adaptation and Natural Selection cast serious doubt on group selection as a major mechanism of evolution; Williams's 1971 book Group Selection assembled writings from many authors on the same theme. It was in the 1960s generally agreed that group selection also applied for eusocial insects such as honeybees. ==Kin selection and inclusive fitness theory== and Elliott Sober's 1994 Multilevel Selection Model, illustrated by a nested set of Russian matryoshka dolls. Wilson himself compared his model to such a set. |alt=David Sloan Wilson compared multilevel selection to a nested set of Russian dolls D. S. Wilson compared the layers of competition and evolution to nested sets of Russian matryoshka dolls. The lowest level is the genes, next come the cells, then the organism level and finally the groups. The different levels function cohesively to maximize fitness, or reproductive success. The theory asserts that selection for the group level, involving competition between groups, must outweigh the individual level, involving individuals competing within a group, for a group-benefiting trait to spread. Multilevel selection theory focuses on the phenotype because it looks at the levels that selection directly acts upon. For humans, social norms can be argued to reduce individual level variation and competition, thus shifting selection to the group level. The assumption is that variation between different groups is larger than variation within groups. Competition and selection can operate at all levels regardless of scale. D. S. Wilson wrote, "At all scales, there must be mechanisms that coordinate the right kinds of action and prevent disruptive forms of self-serving behavior at lower levels of social organization." E. O. Wilson summarized, "In a group, selfish individuals beat altruistic individuals. But, groups of altruistic individuals beat groups of selfish individuals." D. S. Wilson argues that while kin selection works well for the behaviour of many animals, human behaviour is difficult to explain using kin selection alone. In particular, he claims it does not explain the rapid rise of human civilization, and that other factors must be considered. He and others have continued to develop group selection models. He ties the multilevel selection theory regarding humans to another theory, gene–culture coevolution, by acknowledging that culture seems to characterize a group-level mechanism for human groups to adapt to environmental changes. D. S. Wilson and Sober's work revived interest in multilevel selection. In a 2005 article, E. O. Wilson argued that kin selection could no longer be thought of as underlying the evolution of extreme sociality, for two reasons. First, he suggested, the argument that haplodiploid inheritance (as in the Hymenoptera) creates a strong selection pressure towards nonreproductive castes is mathematically flawed. Second, eusociality no longer seems to be confined to the hymenopterans; increasing numbers of highly social taxa have been found in the years since E. O. Wilson's foundational text Sociobiology: A New Synthesis was published in 1975¹. These including a variety of insect species, as well as two rodent species (the naked mole-rat and the Damaraland mole rat). E. O. Wilson suggests that the equation for Hamilton's rule: rb > c (where b represents the benefit to the recipient of altruism, c the cost to the altruist, and r their degree of relatedness) should be replaced by the more general equation rb k + b e > c in which b k is the benefit to kin (b in the original equation) and b e is the benefit accruing to the group as a whole. He then argues that, in the present state of the evidence in relation to social insects, it appears that b e >rb k , so that altruism needs to be explained in terms of selection at the colony level rather than at the kin level. However, kin selection and group selection are not distinct processes, and the effects of multi-level selection are already accounted for in Hamilton's rule, rb>c, provided that an expanded definition of r, not requiring Hamilton's original assumption of direct genealogical relatedness, is used, as proposed by E. O. Wilson himself. ==Applications== ===Implications in population biology=== Altruism and group relationships can impact many aspects of population dynamics, such as intraspecific competition and interspecific interactions. In 1871, Darwin argued that group selection occurs when the benefits of cooperation or altruism between subpopulations are greater than the individual benefits of egotism within a subpopulation. This supports the idea of multilevel selection, but kinship also plays an integral role because many subpopulations are composed of closely related individuals. An example of this can be found in lions, which are simultaneously cooperative and territorial. Within a pride, males protect the pride from outside males, and females, who are commonly sisters, communally raise cubs and hunt. However, this cooperation seems to be density dependent. When resources are limited, group selection favours prides that work together to hunt. When prey is abundant, cooperation is no longer beneficial enough to outweigh the disadvantages of altruism, and hunting is no longer cooperative. Interactions between different species, including predator-prey relationships, can be affected by multilevel selection. Individuals of certain monkey species howl to warn the group of the approach of a predator. The evolution of this trait benefits the group by providing protection, but could be disadvantageous to the individual if the howling draws the predator's attention to them. By affecting these interspecific interactions, multilevel and kinship selection can change the population dynamics of an ecosystem. Multilevel selection attempts to explain the evolution of altruism in terms of quantitative genetics. Increased frequency or fixation of altruistic alleles can be accomplished through kin selection, in which individuals behave altruistically to promote the fitness of genetically similar individuals such as their siblings. This can lead to inbreeding depression, which typically lowers the overall fitness of a population. However, if altruism were to be selected for through an emphasis on benefit to the group as opposed to relatedness and benefit to kin, both the altruistic trait and genetic diversity could be preserved. Relatedness should still remain a key consideration in studies of multilevel selection. Experimentally imposed multilevel selection on Japanese quail was some ten times more effective on closely related kin groups than on randomized groups of individuals. ===Gene-culture coevolution in humans=== , leading to complex cultural artefacts like the gopuram of the Sri Mariammam temple, Singapore.|alt=Gene-culture coevolution allows humans to develop complex artefacts like elaborately decorated temples Gene-culture coevolution (also called dual inheritance theory) is a modern hypothesis (applicable mostly to humans) that combines evolutionary biology and modern sociobiology to indicate group selection. It is believed that this approach of combining genetic influence with cultural influence over several generations is not present in the other hypotheses such as reciprocal altruism and kin selection, making gene-culture evolution one of the strongest realistic hypotheses for group selection. Fehr provides evidence of group selection taking place in humans presently with experimentation through logic games such as prisoner's dilemma, the type of thinking that humans have developed many generations ago. Gene-culture coevolution allows humans to develop highly distinct adaptations to the local pressures and environments more quickly than with genetic evolution alone. Robert Boyd and Peter J. Richerson, two strong proponents of cultural evolution, postulate that the act of social learning, or learning in a group as done in group selection, allows human populations to accrue information over many generations. This leads to cultural evolution of behaviours and technology alongside genetic evolution. Boyd and Richerson believe that the ability to collaborate evolved during the Middle Pleistocene, a million years ago, in response to a rapidly changing climate. In 2003, the ethologist Herbert Gintis examined cultural evolution statistically, offering evidence that societies that promote pro-social norms have higher survival rates than societies that do not. Gintis wrote that genetic and cultural evolution can work together. Genes transfer information in DNA, and cultures transfer information encoded in brains, artifacts, or documents. Language, tools, lethal weapons, fire, cooking, etc., have a long-term effect on genetics. For example, cooking led to a reduction of size of the human gut, since less digestion is needed for cooked food. Language led to a change in the human larynx and an increase in brain size. Projectile weapons led to changes in human hands and shoulders, such that humans are much better at throwing objects than the closest human relative, the chimpanzee. In 2015, William Yaworsky and colleagues surveyed the opinions of anthropologists on group selection, finding that these varied with the gender and politics of the social scientists concerned. In 2019, Howard Rachlin and colleagues proposed group selection of behavioural patterns, such as learned altruism, during ontogeny parallel to group selection during phylogeny. ==External links== Lloyd, Elisabeth, "Units and Levels of Selection." The Stanford Encyclopedia of Philosophy, (Fall 2005 Edition), Edward N. Zalta (ed.) The Controversy of the Group Selection Theory – a review from the "Science Creative Quarterly" (a blog) Binghamton: D.S. Wilson

Text derived from https://en.wikipedia.org/w/index.php?oldid=1376327239 under CC BY-SA 4.0; modifications have been made.