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Group selection is a proposed mechanism of
evolution Evolution is change in the heritable characteristics of biological populations over successive generations. These characteristics are the expressions of genes, which are passed on from parent to offspring during reproduction. Variation ...
in which
natural selection Natural selection is the differential survival and reproduction of individuals due to differences in phenotype. It is a key mechanism of evolution, the change in the heritable traits characteristic of a population over generations. Cha ...
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 Konrad Zacharias Lorenz (; 7 November 1903 – 27 February 1989) was an Austrian zoologist, ethologist, and ornithologist. He shared the 1973 Nobel Prize in Physiology or Medicine with Nikolaas Tinbergen and Karl von Frisch. He is often regarde ...
argued that the behavior of animals could affect their survival and reproduction as groups, speaking for instance of actions for the good of the species. In the 1930s,
R.A. Fisher Sir Ronald Aylmer Fisher (17 February 1890 – 29 July 1962) was a British polymath who was active as a mathematician, statistician, biologist, geneticist, and academic. For his work in statistics, he has been described as "a genius who ...
and J.B.S. Haldane proposed the concept of
kin selection Kin selection is the evolutionary strategy that favours the reproductive success of an organism's relatives, even when at a cost to the organism's own survival and reproduction. Kin altruism can look like altruistic behaviour whose evolution i ...
, a form of altruism from the
gene-centered view of evolution With gene defined as "not just one single physical bit of DNA utall replicas of a particular bit of DNA distributed throughout the world", the gene-centered view of evolution, gene's eye view, gene selection theory, or selfish gene theory hol ...
, 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 Evolutionary biology is the subfield of biology that studies the evolutionary processes (natural selection, common descent, speciation) that produced the diversity of life on Earth. It is also defined as the study of the history of life f ...
such as
John Maynard Smith John Maynard Smith (6 January 1920 – 19 April 2004) was a British theoretical and mathematical evolutionary biologist and geneticist. Originally an aeronautical engineer during the Second World War, he took a second degree in genetics un ...
,
W. D. Hamilton William Donald Hamilton (1 August 1936 – 7 March 2000) was a British evolutionary biologist, recognised as one of the most significant evolutionary theorists of the 20th century. Hamilton became known for his theoretical work expounding a ...
, George C. Williams, and Richard Dawkins argued that
natural selection Natural selection is the differential survival and reproduction of individuals due to differences in phenotype. It is a key mechanism of evolution, the change in the heritable traits characteristic of a population over generations. Cha ...
acted 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 Haplodiploidy is a sex-determination system in which males develop from unfertilized eggs and are haploid, and females develop from fertilized eggs and are diploid. Haplodiploidy is sometimes called arrhenotoky. Haplodiploidy determines the sex ...
social insects like honeybees (in the Hymenoptera), 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 David Sloan Wilson (born 1949) is an American evolutionary biologist and a Distinguished Professor Emeritus of Biological Sciences and Anthropology at Binghamton University. He is a son of author Sloan Wilson, and co-founder of the Evolution ...
and
Elliott Sober Elliott R. Sober (born 6 June 1948) is Hans Reichenbach Professor and William F. Vilas Research Professor in the Department of Philosophy at University of Wisconsin–Madison. Sober is noted for his work in philosophy of biology and general phil ...
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 Edward Osborne Wilson (June 10, 1929 – December 26, 2021) was an American biologist, naturalist, entomologist and writer. According to David Attenborough, Wilson was the world's leading expert in his specialty of myrmecology, the study of an ...
, known for his work on social insects especially
ant Ants are eusocial insects of the family Formicidae and, along with the related wasps and bees, belong to the order Hymenoptera. Ants evolved from vespoid wasp ancestors in the Cretaceous period. More than 13,800 of an estimated total of ...
s, 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, provoking a strong rebuttal from a large group of ethologists.


Early developments

Charles Darwin Charles Robert Darwin ( ; 12 February 1809 – 19 April 1882) was an English naturalist, geologist, and biologist, widely known for his contributions to evolutionary biology. His proposition that all species of life have descended ...
developed the
theory of evolution Evolution is change in the heritable characteristics of biological populations over successive generations. These characteristics are the expressions of genes, which are passed on from parent to offspring during reproduction. Variatio ...
in his book, ''
Origin of Species ''On the Origin of Species'' (or, more completely, ''On the Origin of Species by Means of Natural Selection, or the Preservation of Favoured Races in the Struggle for Life''),The book's full original title was ''On the Origin of Species by Me ...
''. Darwin also made the first suggestion of group selection in ''
The Descent of Man ''The Descent of Man, and Selection in Relation to Sex'' is a book by English naturalist Charles Darwin, first published in 1871, which applies evolutionary theory to human evolution, and details his theory of sexual selection, a form of biol ...
'' 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 Modern synthesis or modern evolutionary synthesis refers to several perspectives on evolutionary biology, namely: * Modern synthesis (20th century), the term coined by Julian Huxley in 1942 to denote the synthesis between Mendelian genetics and s ...
of the mid-twentieth century, animal behavior was glibly explained with unsubstantiated hypotheses about survival value, which was largely taken for granted. The naturalist
Konrad Lorenz Konrad Zacharias Lorenz (; 7 November 1903 – 27 February 1989) was an Austrian zoologist, ethologist, and ornithologist. He shared the 1973 Nobel Prize in Physiology or Medicine with Nikolaas Tinbergen and Karl von Frisch. He is often regarde ...
had argued loosely in books like ''
On Aggression ''On Aggression'' (german: Das sogenannte Böse. Zur Naturgeschichte der Aggression, "So-called Evil: on the natural history of aggression") is a 1963 book by the ethologist Konrad Lorenz; it was translated into English in 1966. As he writes in th ...
'' (1966) that animal behavior patterns were "for the good of the species", without actually studying survival value in the field. Richard Dawkins noted 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 Ethology is the scientific study of animal behaviour, usually with a focus on behaviour under natural conditions, and viewing behaviour as an evolutionarily adaptive trait. Behaviourism as a term also describes the scientific and objectiv ...
Niko Tinbergen Nikolaas "Niko" Tinbergen (; ; 15 April 1907 – 21 December 1988) was a Dutch biologist and ornithologist who shared the 1973 Nobel Prize in Physiology or Medicine with Karl von Frisch and Konrad Lorenz for their discoveries concerning the or ...
praised Lorenz for his interest in the survival value of behavior, 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, Richard Dawkins wrote a well-known book on the importance of evolution at the level of the
gene In biology, the word gene (from , ; "... Wilhelm Johannsen coined the word gene to describe the Mendelian units of heredity..." meaning ''generation'' or ''birth'' or ''gender'') can have several different meanings. The Mendelian gene is a b ...
or the individual, ''
The Selfish Gene ''The Selfish Gene'' is a 1976 book on evolution by the ethologist Richard Dawkins, in which the author builds upon the principal theory of George C. Williams's '' Adaptation and Natural Selection'' (1966). Dawkins uses the term "selfish gen ...
''. From the mid 1960s,
evolutionary biologists Evolutionary biology is the subfield of biology that studies the evolutionary processes (natural selection, common descent, speciation) that produced the diversity of life on Earth. It is also defined as the study of the history of life f ...
argued that
natural selection Natural selection is the differential survival and reproduction of individuals due to differences in phenotype. It is a key mechanism of evolution, the change in the heritable traits characteristic of a population over generations. Cha ...
acted primarily at the level of the individual. In 1964,
John Maynard Smith John Maynard Smith (6 January 1920 – 19 April 2004) was a British theoretical and mathematical evolutionary biologist and geneticist. Originally an aeronautical engineer during the Second World War, he took a second degree in genetics un ...
, C. M. Perrins (1964), and George C. Williams in his 1966 book ''
Adaptation and Natural Selection ''Adaptation and Natural Selection: A Critique of Some Current Evolutionary Thought'' is a 1966 book by the American evolutionary biologist George C. Williams. Williams, in what is now considered a classic by evolutionary biologists, outlines a ...
'' cast serious doubt on group selection as a major mechanism of evolution; Williams's 1971 book ''
Group Selection 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 behavi ...
'' assembled writings from many authors on the same theme. It was at that time generally agreed that this was the case even for
eusocial Eusociality (from Greek εὖ ''eu'' "good" and social), the highest level of organization of sociality, is defined by the following characteristics: cooperative brood care (including care of offspring from other individuals), overlapping gen ...
insects such as
honeybee A honey bee (also spelled honeybee) is a eusocial flying insect within the genus ''Apis'' of the bee clade, all native to Afro-Eurasia. After bees spread naturally throughout Africa and Eurasia, humans became responsible for the current cosm ...
s, which encourages
kin selection Kin selection is the evolutionary strategy that favours the reproductive success of an organism's relatives, even when at a cost to the organism's own survival and reproduction. Kin altruism can look like altruistic behaviour whose evolution i ...
, since workers are closely related.


Kin selection and inclusive fitness theory

Experiments from the late 1970s suggested that selection involving groups was possible. Early group selection models assumed that genes acted independently, for example a gene that coded for cooperation or altruism. Genetically based reproduction of individuals implies that, in group formation, the altruistic genes would need a way to act for the benefit of members in the group to enhance the fitness of many individuals with the same gene. But it is expected from this model that individuals of the same species would compete against each other for the same resources. This would put cooperating individuals at a disadvantage, making genes for cooperation likely to be eliminated. Group selection on the level of the species is flawed because it is difficult to see how selective pressures would be applied to competing/non-cooperating individuals.
Kin selection Kin selection is the evolutionary strategy that favours the reproductive success of an organism's relatives, even when at a cost to the organism's own survival and reproduction. Kin altruism can look like altruistic behaviour whose evolution i ...
between related individuals is accepted as an explanation of altruistic behavior.
R.A. Fisher Sir Ronald Aylmer Fisher (17 February 1890 – 29 July 1962) was a British polymath who was active as a mathematician, statistician, biologist, geneticist, and academic. For his work in statistics, he has been described as "a genius who ...
in 1930 and J.B.S. Haldane in 1932 set out the mathematics of kin selection, with Haldane famously joking that he would willingly die for two brothers or eight cousins. (see also: Haldane's Wikiquote entry) In this model, genetically related individuals cooperate because survival advantages to one individual also benefit kin who share some fraction of the same genes, giving a mechanism for favoring genetic selection.
Inclusive fitness In evolutionary biology, inclusive fitness is one of two metrics of evolutionary success as defined by W. D. Hamilton in 1964: * Personal fitness is the number of offspring that an individual begets (regardless of who rescues/rears/supports them ...
theory, first proposed by
W. D. Hamilton William Donald Hamilton (1 August 1936 – 7 March 2000) was a British evolutionary biologist, recognised as one of the most significant evolutionary theorists of the 20th century. Hamilton became known for his theoretical work expounding a ...
in the early 1960s, gives a selection criterion for evolution of social traits when social behavior is costly to an individual organism's survival and reproduction. The criterion is that the reproductive benefit to relatives who carry the social trait, multiplied by their relatedness (the probability that they share the altruistic trait) exceeds the cost to the individual. Inclusive fitness theory is a general treatment of the statistical probabilities of social traits accruing to any other organisms likely to propagate a copy of the same social trait. Kin selection theory treats the narrower but simpler case of the benefits to close genetic relatives (or what biologists call 'kin') who may also carry and propagate the trait. A significant group of biologists support inclusive fitness as the explanation for social behavior in a wide range of species, as supported by experimental data. An article was published in ''
Nature Nature, in the broadest sense, is the physical world or universe. "Nature" can refer to the phenomena of the physical world, and also to life in general. The study of nature is a large, if not the only, part of science. Although humans are ...
'' with over a hundred coauthors. One of the questions about kin selection is the requirement that individuals must know if other individuals are related to them, or
kin recognition Kin recognition, also called kin detection, is an organism's ability to distinguish between close genetic kin and non-kin. In evolutionary biology and psychology, such an ability is presumed to have evolved for inbreeding avoidance, though animals d ...
. Any altruistic act has to preserve similar genes. One argument given by Hamilton is that many individuals operate in "viscous" conditions, so that they live in physical proximity to relatives. Under these conditions, they can act altruistically to any other individual, and it is likely that the other individual will be related. This population structure builds a continuum between individual selection, kin selection, kin group selection and group selection without a clear boundary for each level. However, early theoretical models by D.S. Wilson et al. and Taylor showed that pure population viscosity cannot lead to cooperation and altruism. This is because any benefit generated by kin cooperation is exactly cancelled out by kin competition; additional offspring from cooperation are eliminated by local competition. Mitteldorf and D. S. Wilson later showed that if the population is allowed to fluctuate, then local populations can temporarily store the benefit of local cooperation and promote the evolution of cooperation and altruism. By assuming individual differences in adaptations, Yang further showed that the benefit of local altruism can be stored in the form of offspring quality and thus promote the evolution of altruism even if the population does not fluctuate. This is because local competition among more individuals resulting from local altruism increases the average local fitness of the individuals that survive. Another explanation for the recognition of genes for altruism is that a single trait, group reciprocal kindness, is capable of explaining the vast majority of altruism that is generally accepted as "good" by modern societies. The phenotype of altruism relies on recognition of the altruistic behavior by itself. The trait of kindness will be recognized by sufficiently intelligent and undeceived organisms in other individuals with the same trait. Moreover, the existence of such a trait predicts a tendency for kindness to unrelated organisms that are apparently kind, even if the organisms are of another species. The gene need not be exactly the same, so long as the effect or phenotype is similar. Multiple versions of the gene—or even meme—would have virtually the same effect. This explanation was given by Richard Dawkins as an analogy of a man with a green beard. Green-bearded men are imagined as tending to cooperate with each other simply by seeing a green beard, where the green beard trait is incidentally linked to the reciprocal kindness trait.


Multilevel selection theory

Kin selection or inclusive fitness is accepted as an explanation for cooperative behavior in many species, but the scientist
David Sloan Wilson David Sloan Wilson (born 1949) is an American evolutionary biologist and a Distinguished Professor Emeritus of Biological Sciences and Anthropology at Binghamton University. He is a son of author Sloan Wilson, and co-founder of the Evolution ...
argues that human behavior is difficult to explain with only this approach. In particular, he claims it does not seem to explain the rapid rise of human civilization. Wilson has argued that other factors must also be considered in evolution. Wilson and others have continued to develop group selection models. Early group selection models were flawed because they assumed that genes acted independently; but genetically based interactions among individuals are ubiquitous in group formation because genes must cooperate for the benefit of association in groups to enhance the fitness of group members. Additionally, group selection on the level of the species is flawed because it is difficult to see how selective pressures would be applied; selection in social species of groups against other groups, rather than the species entire, seems to be the level at which selective pressures are plausible. On the other hand, kin selection is accepted as an explanation of altruistic behavior. Some biologists argue that kin selection and multilevel selection are both needed to "obtain a complete understanding of the evolution of a social behavior system". In 1994 David Sloan Wilson and
Elliott Sober Elliott R. Sober (born 6 June 1948) is Hans Reichenbach Professor and William F. Vilas Research Professor in the Department of Philosophy at University of Wisconsin–Madison. Sober is noted for his work in philosophy of biology and general phil ...
argued that the case against group selection had been overstated. They considered whether groups can have functional organization in the same way as individuals, and consequently whether groups can be "vehicles" for
selection Selection may refer to: Science * Selection (biology), also called natural selection, selection in evolution ** Sex selection, in genetics ** Mate selection, in mating ** Sexual selection in humans, in human sexuality ** Human mating strateg ...
. They do not posit evolution on the level of the species, but selective pressures that winnow out small groups within a species, e.g. groups of social insects or primates. Groups that cooperate better might survive and reproduce more than those that did not. Resurrected in this way, Wilson & Sober's new group selection is called multilevel selection theory. In 2010,
Martin Nowak Martin Andreas Nowak (born April 7, 1965) is an Austrian-born professor of mathematical biology, at Harvard University since 2003. He is one of the leading researchers in the field that studies the role of cooperation in evolution. Nowak has hel ...
, C. E. Tarnita and
E. O. Wilson Edward Osborne Wilson (June 10, 1929 – December 26, 2021) was an American biologist, naturalist, entomologist and writer. According to David Attenborough, Wilson was the world's leading expert in his specialty of myrmecology, the study of an ...
argued for multi-level selection, including group selection, to correct what they saw as deficits in the explanatory power of inclusive fitness. A response from 137 other evolutionary biologists argued "that their arguments are based upon a misunderstanding of evolutionary theory and a misrepresentation of the empirical literature". Wilson compared the layers of competition and evolution to nested sets of Russian
matryoshka doll Matryoshka dolls ( ; rus, матрёшка, p=mɐˈtrʲɵʂkə, a=Ru-матрёшка.ogg), also known as stacking dolls, nesting dolls, Russian tea dolls, or Russian dolls, are a set of wooden dolls of decreasing size placed one inside ano ...
s. The lowest level is the
gene In biology, the word gene (from , ; "... Wilhelm Johannsen coined the word gene to describe the Mendelian units of heredity..." meaning ''generation'' or ''birth'' or ''gender'') can have several different meanings. The Mendelian gene is a b ...
s, next come the cells, then the
organism In biology, an organism () is any living system that functions as an individual entity. All organisms are composed of cells (cell theory). Organisms are classified by taxonomy into groups such as multicellular animals, plants, and ...
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. 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." Wilson ties the multilevel selection theory regarding humans to another theory,
gene-culture coevolution Dual inheritance theory (DIT), also known as gene–culture coevolution or biocultural evolution, was developed in the 1960s through early 1980s to explain how human behavior is a product of two different and interacting evolutionary processes: ge ...
, by acknowledging that culture seems to characterize a group-level mechanism for human groups to adapt to environmental changes. MLS theory can be used to evaluate the balance between group selection and individual selection in specific cases. An experiment by William Muir compared egg productivity in hens, showing that a hyper-aggressive strain had been produced through individual selection, leading to many fatal attacks after only six generations; by implication, it could be argued that group selection must have been acting to prevent this in real life. Group selection has most often been postulated in humans and, notably,
eusocial Eusociality (from Greek εὖ ''eu'' "good" and social), the highest level of organization of sociality, is defined by the following characteristics: cooperative brood care (including care of offspring from other individuals), overlapping gen ...
Hymenoptera that make cooperation a driving force of their adaptations over time and have a unique system of inheritance involving
haplodiploidy Haplodiploidy is a sex-determination system in which males develop from unfertilized eggs and are haploid, and females develop from fertilized eggs and are diploid. Haplodiploidy is sometimes called arrhenotoky. Haplodiploidy determines the sex ...
that allows the colony to function as an individual while only the queen reproduces. 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 Haplodiploidy is a sex-determination system in which males develop from unfertilized eggs and are haploid, and females develop from fertilized eggs and are diploid. Haplodiploidy is sometimes called arrhenotoky. Haplodiploidy determines the sex ...
inheritance (as in the Hymenoptera) creates a strong selection pressure towards nonreproductive castes is mathematically flawed. Second,
eusociality Eusociality (from Greek εὖ ''eu'' "good" and social), the highest level of organization of sociality, is defined by the following characteristics: cooperative brood care (including care of offspring from other individuals), overlapping generat ...
no longer seems to be confined to the hymenopterans; increasing numbers of highly social taxa have been found in the years since Wilson's foundational text '' Sociobiology: A New Synthesis'' was published in 1975. These including a variety of insect species, as well as two rodent species (the
naked mole-rat The naked mole-rat (''Heterocephalus glaber''), also known as the sand puppy, is a burrowing rodent native to the Horn of Africa and parts of Kenya, notably in Somali regions. It is closely related to the blesmols and is the only species in the ...
and the Damaraland mole rat). Wilson suggests 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 :::rbk + be > c in which bk is the benefit to kin (b in the original equation) and be 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 be>rbk, 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. Spatial populations of predators and prey show restraint of reproduction at equilibrium, both individually and through social communication, as originally proposed by Wynne-Edwards. While these spatial populations do not have well-defined groups for group selection, the local spatial interactions of organisms in transient groups are sufficient to lead to a kind of multi-level selection. There is however as yet no evidence that these processes operate in the situations where Wynne-Edwards posited them. Rauch et al.'s analysis of host-
parasite Parasitism is a close relationship between species, where one organism, the parasite, lives on or inside another organism, the host, causing it some harm, and is adapted structurally to this way of life. The entomologist E. O. Wilson has ...
evolution is broadly hostile to group selection. Specifically, the parasites do not individually moderate their transmission; rather, more transmissible variants – which have a short-term but unsustainable advantage – arise, increase, and go extinct.


Applications


Differing evolutionarily stable strategies

The problem with group selection is that for a whole group to get a single trait, it must spread through the whole group first by regular evolution. But, as J. L. Mackie suggested, when there are many different groups, each with a different
evolutionarily stable strategy An evolutionarily stable strategy (ESS) is a strategy (or set of strategies) that is ''impermeable'' when adopted by a population in adaptation to a specific environment, that is to say it cannot be displaced by an alternative strategy (or set o ...
, there is selection between the different strategies, since some are worse than others. For example, a group where altruism was universal would indeed outcompete a group where every creature acted in its own interest, so group selection might seem feasible; but a mixed group of altruists and non-altruists would be vulnerable to cheating by non-altruists within the group, so group selection would collapse.


Implications in population biology

Social behaviors such as altruism and group relationships can impact many aspects of population dynamics, such as
intraspecific competition Intraspecific competition is an interaction in population ecology, whereby members of the same species compete for limited resources. This leads to a reduction in fitness for both individuals, but the more fit individual survives and is able to r ...
and
interspecific Biological specificity is the tendency of a characteristic such as a behavior or a biochemical variation to occur in a particular species. Biochemist Linus Pauling stated that "Biological specificity is the set of characteristics of living organi ...
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 favors 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 can also be affected by multilevel selection. Predator-prey relationships can also be affected. 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 altruistic behavior in terms of
quantitative genetics Quantitative genetics deals with phenotypes that vary continuously (such as height or mass)—as opposed to discretely identifiable phenotypes and gene-products (such as eye-colour, or the presence of a particular biochemical). Both branches u ...
. Increased frequency or fixation of altruistic
allele An allele (, ; ; modern formation from Greek ἄλλος ''állos'', "other") is a variation of the same sequence of nucleotides at the same place on a long DNA molecule, as described in leading textbooks on genetics and evolution. ::"The chro ...
s can be accomplished through kin selection, in which individuals engage in altruistic behavior to promote the fitness of genetically similar individuals such as siblings. However, this can lead to
inbreeding depression Inbreeding depression is the reduced biological fitness which has the potential to result from inbreeding (the breeding of related individuals). Biological fitness refers to an organism's ability to survive and perpetuate its genetic material. ...
, 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. However, relatedness should still remain a key consideration in studies of multilevel selection. Experimentally imposed multilevel selection on Japanese quail was more effective by an order of magnitude on closely related kin groups than on randomized groups of individuals.


Gene-culture coevolution in humans

Gene-culture coevolution Dual inheritance theory (DIT), also known as gene–culture coevolution or biocultural evolution, was developed in the 1960s through early 1980s to explain how human behavior is a product of two different and interacting evolutionary processes: ge ...
(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 behaviors and technology alongside genetic evolution. Boyd and Richerson believe that the ability to collaborate evolved during the Middle
Pleistocene The Pleistocene ( , often referred to as the ''Ice age'') is the geological epoch that lasted from about 2,580,000 to 11,700 years ago, spanning the Earth's most recent period of repeated glaciations. Before a change was finally confirmed in ...
, a million years ago, in response to a rapidly changing climate. In 2003, the behavioral scientist
Herbert Gintis Herbert Gintis (February 11, 1940 – January 5, 2023) was an American economist, behavioral scientist, and educator known for his theoretical contributions to sociobiology, especially altruism, cooperation, epistemic game theory, gene-culture co ...
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.


Criticism

The vast majority of behavioural biologists have not been convinced by renewed attempts to revisit group selection as a plausible mechanism of evolution. The use of the
Price equation In the theory of evolution and natural selection, the Price equation (also known as Price's equation or Price's theorem) describes how a trait or allele changes in frequency over time. The equation uses a covariance between a trait and fitness, ...
to support group selection was challenged by van Veelen in 2012, arguing that it is based on invalid mathematical assumptions. Advocates of the
gene-centered view of evolution With gene defined as "not just one single physical bit of DNA utall replicas of a particular bit of DNA distributed throughout the world", the gene-centered view of evolution, gene's eye view, gene selection theory, or selfish gene theory hol ...
such as Dawkins and Daniel Dennett remain unconvinced about group selection.See the chapter ''
God's utility function ''River Out of Eden: A Darwinian View of Life'' is a 1995 popular science book by Richard Dawkins. The book is about Darwinian evolution and summarizes the topics covered in his earlier books, '' The Selfish Gene'', '' The Extended Phenotype'' ...
'' in
Dawkins suggests that group selection fails to make an appropriate distinction between replicators and vehicles. The evolutionary biologist
Jerry Coyne Jerry may refer to: Animals * Jerry (Grand National winner), racehorse, winner of the 1840 Grand National * Jerry (St Leger winner), racehorse, winner of 1824 St Leger Stakes Arts, entertainment, and media * ''Jerry'' (film), a 2006 Indian fi ...
summarizes the arguments in ''
The New York Review of Books ''The New York Review of Books'' (or ''NYREV'' or ''NYRB'') is a semi-monthly magazine with articles on literature, culture, economics, science and current affairs. Published in New York City, it is inspired by the idea that the discussion of i ...
'' in non-technical terms as follows: The psychologist
Steven Pinker Steven Arthur Pinker (born September 18, 1954) is a Canadian-American cognitive psychologist, psycholinguist, popular science author, and public intellectual. He is an advocate of evolutionary psychology and the computational theory of mind. ...
states that "group selection has no useful role to play in psychology or social science", since in these domains it "is not a precise implementation of the theory of natural selection, as it is, say, in genetic algorithms or
artificial life Artificial life (often abbreviated ALife or A-Life) is a field of study wherein researchers examine systems related to natural life, its processes, and its evolution, through the use of simulations with computer models, robotics, and biochemistry ...
simulations. Instead n psychologyit is a loose metaphor, more like the struggle among kinds of tires or telephones."


References


Further reading

* * * * * * * * *


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 A blog (a truncation of "weblog") is a discussion or informational website published on the World Wide Web consisting of discrete, often informal diary-style text entries (posts). Posts are typically displayed in reverse chronological order s ...
)
Binghamton: D.S. Wilson
{{DEFAULTSORT:Group Selection Selection Population genetics Extended evolutionary synthesis