Instruct: Given a question, retrieve relevant passages that answer the question.
Query: Who identified inclusive fitness theory?
In evolutionary biology, inclusive fitness is one of two metrics of evolutionary success as defined by W. D. Hamilton in 1964:
Inclusive fitness theory was developed in order to better understand collateral altruism, but this does not mean that it is limited to collateral altruism. It applies just as well to parental care. Which perspective one chooses does not affect the animals but just one's understanding.
Ultimately these analyses were considered unsuccessful, and were specifically criticized by other sociobiologists on a number of grounds. One problem was said to be that interpreting inclusive fitness theory to imply that individuals have evolved the characteristic of pursuing strategies to maximize their own 'inclusive fitness' is erroneous; the theory should instead be interpreted to describe selection pressures on genes:
Kin selection causes changes in gene frequency across generations, driven by interactions between related individuals. This dynamic forms the conceptual basis of the theory of social evolution. Some cases of evolution by natural selection can only be understood by considering how biological relatives influence each other's fitness. Under natural selection, a gene encoding a trait that enhances the fitness of each individual carrying it should increase in frequency within the population; and conversely, a gene that lowers the individual fitness of its carriers should be eliminated. However, a hypothetical gene that prompts behaviour which enhances the fitness of relatives but lowers that of the individual displaying the behaviour, may nonetheless increase in frequency, because relatives often carry the same gene. According to this principle, the enhanced fitness of relatives can at times more than compensate for the fitness loss incurred by the individuals displaying the behaviour, making kin selection possible. This is a special case of a more general model, "inclusive fitness". This analysis has been challenged, Wilson writing that "the foundations of the general theory of inclusive fitness based on the theory of kin selection have crumbled" and that he now relies instead on the theory of eusociality and "gene-culture co-evolution" for the underlying mechanics of sociobiology.
These two alternative suggestions had important effects on how field biologists understood the theory and what they looked for in the behavior of organisms. Within a few years biologists were looking for evidence that 'kin recognition' mechanisms might occur in organisms, assuming this was a necessary prediction of inclusive fitness theory, leading to a sub-field of 'kin recognition' research.
Inclusive fitness theory takes the form of an ultimate explanation, specifically a criterion (br>c), for the evolution of social behaviors, not a proximate mechanism governing the expression of social behaviors. What forms of social behavior might meet this criterion are cannot be "a priori" specified by the theory, nor can it shed light on whether the life history of a species provides opportunities for social interactions to occur. Thus, strictly speaking, the interpretation that organisms ‘have evolved to’ direct social behavior towards genetic relatives is not implied by the theory (see also inclusive fitness).
This disagreement is central because of the way the association between blood ties/genetic relationships and altruism are conceptualized by many biologists. It is frequently understood by biologists that inclusive fitness theory makes predictions about "how behaviour is mediated" in both humans and other animals. For example, a recent experiment conducted on humans by the evolutionary psychologist Robin Dunbar and colleagues was, as they understood it, designed "to test the prediction that altruistic behaviour is mediated by Hamilton's rule" (inclusive fitness theory) and more specifically that "If participants follow Hamilton's rule, investment (time for which the [altruistic] position was held) should increase with the recipient's relatedness to the participant. In effect, we tested whether investment flows differentially down channels of relatedness." From their results, they concluded that ""human altruistic behaviour is mediated by Hamilton's rule ... humans behave in such a way as to maximize inclusive fitness: they are more willing to benefit closer relatives than more distantly related individuals."" (Madsen et al. 2007). This position continues to be rejected by social anthropologists as being incompatible with the large amount of ethnographic data on kinship and altruism that their discipline has collected over many decades, that demonstrates that in many human cultures, kinship relationships (accompanied by altruism) do not necessarily map closely onto genetic relationships.
Darwinian anthropology was critiqued by Symonds for its agnosticism as to the psychological mechanisms governing how social behavior is actually expressed in the human species, and its reliance on interpreting inclusive fitness theory to simply imply that "humans have evolved to be inclusive fitness maximizers". This section will review some of the relevant background discussion in inclusive fitness theory to clarify why this position was considered untenable.
Early writings on inclusive fitness theory (including Hamilton 1964) used K in place of B/C. Thus Hamilton's rule was expressed as
In a review of 132 of the top health and fitness apps in the Apple app store, in 2014, using gamification as a method to modify behavior, the authors concluded that "Despite the inclusion of at least some components of gamification, the mean scores of integration of gamification components were still below 50 percent. This was also true for the inclusion of game elements and the use of health behavior theory constructs, thus showing a lack of following any clear industry standard of effective gaming, gamification, or behavioral theory in health and fitness apps."
In addition to the above examples, a wide variety of evidence from mammal species supports the finding that shared context and familiarity mediate social bonding, rather than genetic relatedness "per se". Cross-fostering studies (placing unrelated young in a shared developmental environment) strongly demonstrate that unrelated individuals bond and cooperate just as would normal littermates. The evidence therefore demonstrates that bonding and cooperation are mediated by proximity, shared context and familiarity, not via active recognition of genetic relatedness. This is problematic for those biologists who wish to claim that inclusive fitness theory predicts that social cooperation is "mediated" via genetic relatedness, rather than understanding the theory simply to state that social traits can "evolve" under conditions where there is "statistical" association of genetically related organisms. The former position sees the expression of cooperative behaviour as more or less deterministically caused by genetic relatedness, where the latter position does not. The distinction between cooperation mediated by shared context, and cooperation mediated by genetic relatedness "per se", has significant implications for whether inclusive fitness theory can be seen as compatible with the anthropological evidence on human social patterns or not. The "shared context" perspective is largely compatible, the "genetic relatedness" perspective is not (see below).
Such misunderstandings of inclusive fitness' implications for the study of altruism, even amongst professional biologists utilizing the theory, are widespread, prompting prominent theorists to regularly attempt to highlight and clarify the mistakes.[9] Here is one recent example of attempted clarification from West et al. (2010):
In 1964, William D. Hamilton proposed inclusive fitness theory, emphasizing a "gene's-eye" view of evolution. Hamilton noted that individuals can increase the replication of their genes into the next generation by helping close relatives with whom they share genes survive and reproduce. According to "Hamilton's rule", a self-sacrificing behavior can evolve if it helps close relatives so much that it more than compensates for the individual animal's sacrifice. Inclusive fitness theory resolved the issue of how "altruism" evolved. Other theories also help explain the evolution of altruistic behavior, including evolutionary game theory, tit-for-tat reciprocity, and generalized reciprocity. These theories not only help explain the development of altruistic behavior but also account for hostility toward cheaters (individuals that take advantage of others' altruism).
According to inclusive fitness theory, organisms can gain fitness not just through increasing their own reproductive output, but also via increasing the reproductive output of other individuals that share their genes, especially their close relatives. Individuals are selected to help their relatives when the cost of helping is less than the benefit gained by their relative multiplied by the fraction of genes that they share, i.e. when "Cost < relatedness * Benefit". Under inclusive fitness theory, the necessary conditions for eusociality to evolve are more easily fulfilled by haplodiploid species because of their unusual relatedness structure.
Inclusive fitness theory, first proposed by W. D. Hamilton 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. This behavior could emerge under conditions such that the statistical likelihood that benefits accrue to the survival and reproduction of other organisms whom also carry the social trait. 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" with over a hundred coauthors.
The inclusive fitness theory provides a good overview of possible solutions to the fundamental problem of cooperation. The theory is based on the hypothesis that cooperation helps in transmitting underlying genes to future generations either through increasing the reproductive successes of the individual (direct fitness) or of other individuals who carry the same genes (indirect fitness). Direct benefits can result from simple by-product of cooperation or enforcement mechanisms, while indirect benefits can result from cooperation with genetically similar individuals.
Inclusive fitness theory (and the related kin selection theory) are general theories in evolutionary biology that propose a method to understand the evolution of social behaviours in organisms. While various ideas related to these theories have been influential in the study of the social behaviour of non-human organisms, their application to human behaviour has been debated.
Inclusive fitness theory, proposed by William D. Hamilton, emphasized a "gene's-eye" view of evolution. Hamilton noted that what evolution ultimately selects are genes, not groups or species. From this perspective, individuals can increase the replication of their genes into the next generation not only directly via reproduction, by also indirectly helping close relatives with whom they share genes survive and reproduce. General evolutionary theory, in its modern form, "is" essentially inclusive fitness theory.
Inclusive fitness in humans is the application of inclusive fitness theory to human social behaviour, relationships and cooperation.
In a 2010 paper by Martin Nowak, Corina Tarnita and E. O. Wilson, it was suggested that standard natural selection theory is superior to inclusive fitness theory, stating that the interactions between cost and benefit cannot be explained only in terms of relatedness. This, Nowak said, makes Hamilton's rule at worst superfluous and at best ad hoc.[22] Gardner in turn was critical of the paper, describing it as "a really terrible article", and along with other co-authors has written a reply, submitted to Nature.[23]
In 2010 a paper by Nowak, EO Wilson, and Corina Tarnita, in "Nature", argued that standard natural selection theory represents a simpler and superior approach to kin selection theory in the evolution of eusociality. This work has led to many comments including strong criticism from proponents of inclusive fitness theory. Nowak maintains that the findings of the paper are conclusive and that the field of social evolution should move beyond the limitations imposed by inclusive fitness theory.
Inclusive fitness theory, first proposed by Bill Hamilton in the early 1960s, proposes a selective criterion for the potential evolution of social traits in organisms, where social behavior that is costly to an individual organism's survival and reproduction could nevertheless emerge under certain conditions. The key condition relates to the statistical likelihood that significant benefits of a social trait or behavior accrue to (the survival and reproduction of) other organisms whom also carry the social trait. 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 more straightforward case of the benefits accruing to close genetic relatives (or what biologists call 'kin') who may also carry and propagate the trait. Under conditions where the social trait sufficiently correlates (or more properly, "regresses") with other likely bearers, a net overall increase in reproduction of the social trait in future generations can result.
Whilst the above understanding of inclusive fitness theory as necessarily making predictions about how human kinship and altruism is mediated is common amongst evolutionary psychologists, other biologists and anthropologists have argued that it is at best a limited (and at worst a mistaken) understanding of inclusive fitness theory. These scientists argue that the theory is better understood as simply describing an "evolutionary" criterion for the emergence of altruistic behaviour, which is explicitly statistical in character, not as predictive of "proximate" or "mediating" mechanisms of altruistic behaviour, which may not necessarily be determined by genetic relatedness (or blood ties) "per se". These alternative non-deterministic and non-reductionist understandings of inclusive fitness theory and human behavior have been argued to be compatible with anthropologists' decades of data on human kinship, and compatible with anthropologists' perspectives on human kinship. This position (e.g. nurture kinship) has been largely accepted by social anthropologists, whilst the former position (still held by evolutionary psychologists, see above) remains rejected by social anthropologists.
A common source of confusion around inclusive fitness theory is that Hamilton's early analysis included some inaccuracies, that, "although corrected by him in later publications", are often not fully understood by other researchers who attempt to apply inclusive fitness to understanding organisms' behaviour. For example, Hamilton had initially suggested that the statistical correlation in his formulation could be understood by a correlation coefficient of genetic relatedness, but quickly accepted George Price's correction that a general regression coefficient was the more relevant metric, and together they published corrections in 1970. A related confusion is the connection between inclusive fitness and multi-level selection, which are often incorrectly assumed to be mutually exclusive theories. The regression coefficient helps to clarify this connection:
When coalitions are composed of relatives, the contradictory nature of male reproductive alliances is easily resolved through inclusive fitness theory. The theory of inclusive fitness, proposed by Hamilton (1964) states that individuals can enhance their own reproductive fitness by securing the reproductive success of their relatives 10. For kin selection to increase the reproductive fitness of the altruist, according to Hamilton (1964) as cited in Nowak (2006) the coefficient of relatedness, between the donor and recipient of the altruistic act, must be greater than the cost-to-benefit ratio of the altruist act (r < c/b). In other words, the reproductive benefit gained by the recipient of the altruistic act times the coefficient of relatedness must be greater than the reproductive cost of the individual performing the altruistic act (rb > c). Therefore, in alliances composed of closely related individuals, where there is a large coefficient of relatedness, it is widely believed that inclusive fitness has been the principal driving force for the evolution of male reproductive cooperation.