Evaluating inclusive fitness.
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ABSTRACT:
SUBMITTER: Woodford P
PROVIDER: S-EPMC6599781 | biostudies-literature | 2019 Jun
REPOSITORIES: biostudies-literature
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Project description:Until recently, inclusive fitness has been widely accepted as a general method to explain the evolution of social behavior. Affirming and expanding earlier criticism, we demonstrate that inclusive fitness is instead a limited concept, which exists only for a small subset of evolutionary processes. Inclusive fitness assumes that personal fitness is the sum of additive components caused by individual actions. This assumption does not hold for the majority of evolutionary processes or scenarios. To sidestep this limitation, inclusive fitness theorists have proposed a method using linear regression. On the basis of this method, it is claimed that inclusive fitness theory (i) predicts the direction of allele frequency changes, (ii) reveals the reasons for these changes, (iii) is as general as natural selection, and (iv) provides a universal design principle for evolution. In this paper we evaluate these claims, and show that all of them are unfounded. If the objective is to analyze whether mutations that modify social behavior are favored or opposed by natural selection, then no aspect of inclusive fitness theory is needed.
| S-EPMC3864293 | biostudies-literature
Project description:Cooperation among kin is common across the natural world and can be explained in terms of inclusive fitness theory, which holds that individuals can derive indirect fitness benefits from aiding genetically related individuals. However, human kinship includes not only genetic kin but also kin by marriage: our affines (in-laws) and spouses. Can cooperation between these genetically unrelated kin be reconciled with inclusive fitness theory? Here, we argue that although affinal kin and spouses do not necessarily share genetic ancestry, they may have shared genetic interests in future reproduction and, as such, can derive indirect fitness benefits though cooperating. We use standard inclusive fitness theory to derive a coefficient of shared reproductive interest (s) that predicts altruistic investment both in genetic kin and in spouses and affines. Specifically, a behaviour that reduces the fitness of the actor by c and increases the fitness of the recipient by b will be favoured by natural selection when sb > c We suggest that the coefficient of shared reproductive interest may provide a valuable tool for understanding not only the evolution of human kinship but also cooperation and conflict across the natural world more generally.
| S-EPMC6227869 | biostudies-literature
Project description:This paper attempts to reconcile critics and defenders of inclusive fitness by constructing a synthesis that does justice to the insights of both. I argue that criticisms of the regression-based version of Hamilton's rule, although they undermine its use for predictive purposes, do not undermine its use as an organizing framework for social evolution research. I argue that the assumptions underlying the concept of inclusive fitness, conceived as a causal property of an individual organism, are unlikely to be exactly true in real populations, but they are approximately true given a specific type of weak selection that Hamilton took, on independent grounds, to be responsible for the cumulative assembly of complex adaptation. Finally, I reflect on the uses and limitations of 'design thinking' in social evolution research.
| S-EPMC5541557 | biostudies-other
Project description:The influence of inclusive fitness interests on the evolution of human institutions remains unclear. Religious celibacy constitutes an especially puzzling institution, often deemed maladaptive. Here, we present sociodemographic data from an agropastoralist Buddhist population in western China, where parents sometimes sent a son to the monastery. We find that men with a monk brother father more children, and grandparents with a monk son have more grandchildren, suggesting that the practice is adaptive. We develop a model of celibacy to elucidate the inclusive fitness costs and benefits associated with this behaviour. We show that a minority of sons being celibate can be favoured if this increases their brothers' reproductive success, but only if the decision is under parental, rather than individual, control. These conditions apply to monks in our study site. Inclusive fitness considerations appear to play a key role in shaping parental preferences to adopt this cultural practice.
| S-EPMC9233928 | biostudies-literature
Project description:A recent model shows that altruism can evolve with limited migration and variable group sizes, and the authors claim that kin selection cannot provide a sufficient explanation of their results. It is demonstrated, using a recent reformulation of Hamilton's original arguments, that the model falls squarely within the scope of inclusive fitness theory, which furthermore shows how to calculate inclusive fitness and the relevant relatedness. A distinction is drawn between inclusive fitness, which is a method of analysing social behaviour; and kin selection, a process that operates through genetic similarity brought about by common ancestry, but not by assortation by genotype or by direct assessment of genetic similarity. The recent model is analysed, and it turns out that kin selection provides a sufficient explanation to considerable quantitative accuracy, contrary to the authors' claims. A parallel analysis is possible and would be illuminating for all models of social behaviour in which individuals' effects on each other's offspring numbers combine additively.
| S-EPMC2197210 | biostudies-literature
Project description:BackgroundRepresentation of people with disabilities in fitness centres is lacking, despite initiatives to promote inclusion mainly in the UK and USA. Success creating these inclusive spaces is mixed and few were crafted taking into account attitudes and biases of non-disabled co-members. Inclusive fitness centres have not gained much attention in Denmark, and the campaign 'Fitness for All - fitness for people with physical disabilities' was initiated. The aim of this study was shaped by two key questions; 1) what is the ideal fitness space from the perception of non-disabled fitness users? and 2) how might their dis/ableist attitudes negate inclusion in three future pilot inclusive fitness centres across Denmark?MethodThree focus groups involving 5-7 (total n = 18) adult non-disabled participants were conducted. Aged ranged between 19 and 75 years, both men and women were involved, with fitness centre experiences ranging from 0 to 20+ years. Interviews were transcribed and analysed using Malterud's four-step method of systematic text condensation.ResultsOf most importance was a pleasant atmosphere which should make them feel welcome and comfortable. Good social relations within the space were also highly valued. Participants welcomed people with physical disabilities but predicted many challenges with an inclusive fitness centre and expressed unconscious ableist attitudes.ConclusionThe current study adds essential knowledge regarding how non-disabled people perceive the ideal inclusive fitness centre. A welcoming and inviting atmosphere is essential whereas social skills, ableism, ignorance, and preconceptions are important barriers that may hinder inclusion of participants with disabilities in inclusive fitness centres.
| S-EPMC8325230 | biostudies-literature
Project description:How can altruism evolve or be maintained in a selfish world? Hamilton's rule shows that the former process will occur when rb > c-the benefits to the recipients of an altruistic act b, weighted by the relatedness between the social partners r, exceed the costs to the altruists c-drives altruistic genotypes spreading against nonaltruistic ones. From this rule, we infer that altruistic genotypes will persist in a population by forming a stable heritable polymorphism with nonaltruistic genotypes if rb = c makes inclusive fitness of the two morphs equal. We test this prediction using the data of 12 years of study on a cooperatively breeding bird, the Tibetan ground tit Pseudopodoces humilis, where helping is performed by males only and kin-directed. Individual variation in ever acting as a helper was heritable (h2 = 0.47), and the resultant altruism polymorphism remained stable as indicated by low-level annual fluctuation of the percentage of helpers among all adult males (24-28%). Helpers' indirect fitness gains from increased lifetime reproductive success of related breeders statistically fully compensated for their lifetime direct fitness losses, suggesting that rb = c holds. While our work provides a fundamental support for Hamilton's idea, it highlights the equivalent inclusive fitness returns to altruists and nonaltruists mediated by rb = c as a theoretically and realistically important mechanism to maintain social polymorphism.
| S-EPMC5828573 | biostudies-literature
Project description:Hamilton's force of selection acting against age-specific mortality is constant and maximal prior to the age of first reproduction, before declining to zero at the age of last reproduction. The force of selection acting on age-specific reproduction declines monotonically from birth in a growing or stationary population. Central to these results is the assumption that individuals do not interact with one another. This assumption is violated in social organisms, where an individual's survival and/or reproduction may shape the inclusive fitness of other group members. Yet, it remains unclear how the forces of selection might be modified when inclusive fitness, rather than population growth rate, is considered the appropriate metric for fitness. Here, we derive such inclusive fitness forces of selection, and show that selection on age-specific survival is not always constant before maturity, and can remain above zero in post-reproductive age classes. We also show how the force of selection on age-specific reproduction does not always decline monotonically from birth, but instead depends on the balance of costs and benefits of increasing reproduction to both direct and indirect fitness. Our theoretical framework provides an opportunity to expand our understanding of senescence across social species.
| S-EPMC10480192 | biostudies-literature
Project description:How to define and use the concept of inclusive fitness is a contentious topic in evolutionary theory. Inclusive fitness can be used to calculate selection on a focal gene, but it is also applied to whole organisms. Individuals are then predicted to appear designed as if to maximize their inclusive fitness, provided that certain conditions are met (formally when interactions between individuals are 'additive'). Here we argue that applying the concept of inclusive fitness to organisms is justified under far broader conditions than previously shown, but only if it is appropriately defined. Specifically, we propose that organisms should maximize the sum of their offspring ( including any accrued due to the behaviour/phenotype of relatives), plus any effects on their relatives' offspring production, weighted by relatedness. By contrast, most theoreticians have argued that a focal individual's inclusive fitness should exclude any offspring accrued due to the behaviour of relatives. Our approach is based on the notion that long-term evolution follows the genome's 'majority interest' of building coherent bodies that are efficient 'vehicles' for gene propagation. A gene favoured by selection that reduces the propagation of unlinked genes at other loci (e.g. meiotic segregation distorters that lower sperm production) is eventually neutralized by counter-selection throughout the rest of the genome. Most phenotypes will therefore appear as if designed to maximize the propagation of any given gene in a focal individual and its relatives.
| S-EPMC6571478 | biostudies-literature
Project description:Although over 50 y have passed since W. D. Hamilton articulated kin selection and inclusive fitness as evolutionary explanations for altruistic behavior, quantifying inclusive fitness continues to be challenging. Here, using 30 y of data and two alternative methods, we outline an approach to measure lifetime inclusive fitness effects of cooperative polygamy (mate-sharing or cobreeding) in the cooperatively breeding acorn woodpecker Melanerpes formicivorus. For both sexes, the number of offspring (observed direct fitness) declined while the number of young parented by related cobreeders (observed indirect fitness effect) increased with cobreeding coalition size. Combining these two factors, the observed inclusive fitness effect of cobreeding was greater than breeding singly for males, while the pattern for females depended on whether fitness was age-weighted, as females breeding singly accrued greater fitness at younger ages than cobreeding females. Accounting for the fitness birds would have obtained by breeding singly, however, lifetime inclusive fitness effects declined with coalition size for males, but were greater for females breeding as duos compared to breeding singly, due largely to indirect fitness effects of kin. Our analyses provide a road map for, and demonstrate the importance of, quantifying indirect fitness as a powerful evolutionary force contributing to the costs and benefits of social behaviors.
| S-EPMC10175847 | biostudies-literature