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Predictions and Implications of Inclusive Fitness Theory
This idea has been the subject of much research and debate; the theory proposes that individuals can pass on their genes through their offspring and the reproductive success of genetically related individuals, such as siblings, cousins, or distant relatives. Also known as "kin selection theory", a concept in evolutionary biology, it explains how altruistic traits, such as cooperation and selflessness, can arise and persist in populations despite their apparent cost to the individual.
Prediction of Inclusive Fitness Theory
This views how altruistic behaviours are more likely to arise within populations with high relatednesses, such as family groups or small communities. Several studies have also supported this prediction. For instance, researchers discovered that people were more likely to assist in raising the offspring of their near relations in small, cohesive groups when studying the social behaviour of banded mongooses.
Similarly, researchers discovered that lions were more likely to engage in joint hunting when they were part of a group closely connected to them. The inclusive fitness theory's third consequence is that altruistic actions can persist even in the company of selfish people who do not practice altruism. This hypothesis has been tested in different methods, including computer exercises and mathematical models.
One study, for instance, demonstrated using a computer program that, in the presence of sufficient genetic relatedness, a community of self-centred individuals could even transform into a selfless one. A computer model used in another research demonstrates how just a handful of benevolent people within a community could encourage the spread of such behaviour.
Eusociality in Insects
It is a social structure in which some species forego their reproduction in favour of caring for the young of others. Eusociality is found in insects. Numerous bug species exhibit this behaviour, including ants, bees, and wasps. The reproductive people in these species are frequently closely connected to the non-reproductive labourers, supporting the predictions of this theory.
According to research in the journal 'Proceedings of the National Academy of Sciences', the ability of 'Melipona quadrifasciata' (eusocial bee species) and its workers to cooperate was favourably linked with the degree of genetic relatedness between them. Researchers measured the genetic relatedness of the workers in various colonies using microsatellite analysis. They discovered that workers with greater relatedness were likelier to participate in cooperative behaviours like caring for the offspring and storing food.
Adoption in Humans
In some societies, adoption is joint and may involve taking in a child not biologically related to the adoptive parents. However, studies have shown that adoptive parents are more likely to adopt children biologically related to them or their extended family, supporting the idea that kin selection also plays a role in adoption behaviour.
According to Evolution and Human Behaviour research, adoptive parents were likelier to adopt a kid from their immediate or extended family. According to research that examined adoption trends in a sizable group of Swedish adoptive families, the likelihood of adoption was most significant for children connected to the adoptive parents through a close blood relative, such as a brother or cousin.
Patterns of Helping in the Lives of Women
In one early test of inclusive fitness theory applied to humans, two researchers studied 300 adult women from Los Angeles, ages thirty-five to forty-five. The women described 2,520 instances of receiving help and 2,651 cases of giving help. The predictions −
Among kin, helping will increase as a function of genetic relatedness; and
Among kin, helping will increase as the recipient's reproductive value increases.
As predicted, helping exchanges were more likely to occur with close kin than distant kin, supporting a key prediction from inclusive fitness theory. The second prediction was that helping among kin would be preferentially channelled to those of higher reproductive potential, a prediction that was also supported. Women were far more likely to help their children, nieces, and nephews.
Implications of Inclusive Fitness
At the most general level, the most fundamental conclusion of Hamilton's theory of inclusive fitness is that psychological adaptations are predicted to have developed for diverse forms of kin interaction. Nothing in Hamilton's theory requires that such kinship mechanisms necessarily evolve; after all, in some species, members do not even live with their kin, so selection could not fashion specific kin mechanisms.
However, the theory predicts the overall shape of such kin processes if they arise. We saw that there were many specific problems in parenting and the evolution of parental mechanisms, including the differential favouring of children according to qualities such as the probability of being the child's parent and the reproductive value of the child.
The theory of inclusive fitness renders parenting a particular case of kinship, albeit a crucial special case, because parenting represents just one way of investing in "vehicles" that contain copies of one's genes. Other specific relationships that would have recurred throughout human evolutionary history include sibships, half-sibships, grandparenthood, great childhood, and so on.
Organisms will be more likely to help close genetic relatives, such as siblings and cousins, than distant relatives or non-relatives. This is because close genetic relatives share more of an organism's genes. Helping them can increase the likelihood of those genes being passed on to future generations.
Organisms will more likely engage in altruistic behaviours towards younger, more vulnerable relatives. This is because helping younger relatives can increase their chances of survival and reproduction, thus increasing the likelihood of their shared genes being passed on to future generations.
Organisms will be more likely to engage in reciprocal altruism with genetic relatives. Reciprocal altruism involves organisms helping each other over time, with the understanding that they will receive help in return. Genetic relatives are more likely to engage in reciprocal altruism because they share a more significant proportion of their genes.
Organisms will be more likely to form groups with genetic relatives. This is because forming groups with genetic relatives can increase the likelihood of shared genes being passed on to future generations.
Organisms will more likely engage in kin recognition, distinguishing genetic relatives and non-relatives. Kin recognition can help organisms identify potential kin and engage in behaviours more likely to benefit their inclusive fitness.
Older members of an extended kin family will encourage younger members to behave more altruistically and cooperatively towards collateral kin (kin who are not direct descendants). This is because helping collateral kin can increase the likelihood of shared genes being passed on to future generations.
An individual's position within an extended kin network will be a core component of their self-concept. This means that an individual's beliefs about "who they are" will include kin linkages, such as "son of X," "daughter of Y," or "mother of Z."
People everywhere will be aware of who their "real" relatives are, despite differences in the exact kin terms used across cultures. Inclusive fitness theory suggests that people will be keenly aware of who their genetic relatives are, and this knowledge will inform their behaviours toward others.
Kinship terms will persuade and influence other people, even when no actual kinship is involved. For example, using the kin term "brother" when asking for help may activate the psychology of kinship in the target and increase the likelihood of receiving assistance.
Theory of Kin Selection
The kin selection theory proposes that grandparents may invest differently in their grandchildren based on their level of paternity certainty. In humans, females can be utterly sure of their offspring's paternity, while males can never be entirely sure. This uncertainty creates an adaptive problem for human fathers, and psychological adaptations may have evolved to regulate investment in kin based on genetic certainty.
Grandparents are genetically related to each grandchild by 0.25, making it challenging to predict investment patterns. However, inclusive fitness theory predicts that investment in grandchildren should vary based on genetic relatedness. Maternal grandmothers are expected to invest the most, while paternal grandfathers are expected to invest the least, with maternal grandfathers and paternal grandmothers falling in between. This differential investment is referred to as "discriminative grandparental solicitude."
The double uncertainty for grandfathers makes investing in their grandchildren difficult, while grandmothers whose daughters have children are 100% certain of their genetic relation to their grandchildren. Therefore, the grandmother on the maternal side (MoMo) would invest the most, while the paternal grandfather (FaFa) would invest the least. The maternal grandfather (MoFa) and paternal grandmother (FaMo) would invest somewhere in between due to the potential for genetic linkage to be severed at one point in the line of descent.
The inclusive fitness theory predicts altruistic behaviours are more likely to arise within populations with high relatednesses, such as family groups or small communities. This hypothesis has been tested in various methods, such as computer exercises and mathematical models. Inclusive fitness theory suggests organisms are likelier to help close genetic relatives, such as siblings and cousins, than distant relatives or non-relatives.
They are also more likely to engage in altruistic behaviours towards younger, more vulnerable relatives and to form groups with genetic relatives. Reciprocal altruism involves helping each other over time, with the understanding that they will receive help in return. Organisms will more likely engage in kin recognition, distinguishing genetic relatives and non-relatives.
Older members of an extended kin family will encourage younger members to behave more altruistically and cooperatively towards collateral kin. An individual's position within an extended kin network will be a core component of their self-concept, and people everywhere will be aware of their "real" relatives. Kinship terms will persuade and influence other people, even when no actual kinship is involved.
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