Various fields define this entity, and social scientists have not achieved a strong consensus on what makes a family. Sociologists frequently highlight the family's childrearing role, characterising families as people living together and responsible for creating and nurturing children. On the other hand, anthropologists emphasise kinship, defining families as groupings of parents, unmarried children, and occasionally extended relatives whose lines of ancestry may be traced. Stephen Emlen, an evolutionary scientist, defines families as those circumstances in which offspring continue to interact frequently with their parents into adulthood.
Families are so much a part of human life that we take them for granted. The unique reality is that just 3% of all bird and mammalian species establish families. Why are families so uncommon? Why do most kids in the animal kingdom leave the nest as soon as they are biologically capable, and why do so few remain with their parents into sexual maturity?
The most plausible explanation is that staying in the parental nest (or delaying departure from the nest) has a high reproductive cost. Offspring in simple households do not reproduce while living at home. In extended families, however, parents will frequently deliberately inhibit the reproduction of their offspring (e.g., by interfering with mating efforts) (e.g., by interfering with mating attempts).
Families thus impose two direct costs on their offspring: (1) reproduction is delayed and, in some cases, directly suppressed (possibly the most severe cost), and (2) competition for resources such as food is concentrated rather than dispersed, making life more difficult for both parents and offspring. In the few cases in which families evolve, the reproductive benefits of remaining in the family outweigh the high costs of preceding early reproduction.
Stephen Emlen identifies two sorts of families −
Simple families, in which only one female reproduces (e.g., a mother and her reproductive kids), and
Extended families, in which two or more relatives of the same sex can reproduce. The presence of a breeding male is not required to define a family. When the father is present, the family is referred to as biparental since the mother and the father share specific parental responsibilities.
The family is called matrilineal when the man is gone since the female is in charge of parenting. One distinguishing trait of all families is that kids live with their parents once they reach reproductive age. To summarise, the degree of genetic relatedness and the gender of the target both influence the degree to which individuals monitor their kin's behaviour.
To explain the evolution of families, two primary ideas have been presented. The first is the model of ecological limits. According to this hypothesis, families form when there are a limited number of reproductive vacancies accessible to sexually mature children.
In these circumstances, the cost of remaining in the family and the advantages of leaving are few. Because early reproduction is not possible due to a shortage of reproductive vacancies, the high cost of staying within the family delayed reproduction disappears (i.e., resource niches that provide the opportunity for reproduction). The family benefits model is the second theory. This idea holds that families develop due to the abundance of benefits they bring to their kids.
These advantages include −
Increased survival as a result of assistance and protection from family members
Increased ability to compete later, possibly by acquiring skills or greater size and maturity as a result of staying at home
The possibility of inheriting or sharing the family territory or resources as a result of staying at home
Inclusive fitness advantages gained by being able to help and be helped by genetic relatives while staying at home.
Emlen (1995) combines these two views into a single unified explanation of family origins. His family formation hypothesis is based on three principles. First, families emerge when more kids are generated than available reproductive openings to fill. This assumption is derived from the ecological limitations model. Second, families will develop as children are forced to wait for open reproductive vacancies until they are in a position to compete for them.
Finally, families will form when the advantages of remaining at home are significant, such as higher survival, increased capacity to acquire competition skills, increased access to family resources, and enhanced inclusive fitness benefits. Emlen's family theory is thus a blend of ecological limitations and family benefit models.
The first set of predictions involves the family dynamics of kinship and cooperation.
Families emerge when there are not enough reproductive openings but disband when vacancies become available. Families will be in flux, developing and dissolving depending on the circumstances. This prediction has been validated in a variety of bird species. As new breeding opportunities arose where none previously existed, adult children "flew the coop" and departed home to fill those vacancies, severing an unbroken family.
This prediction implies that sexually mature children who are not yet in a position to compete successfully for mates or who do not have the financial means to support themselves will tend to stay with their family unit.
Families with considerable resources will be more stable and long-lasting than families with fewer resources. Humans would anticipate affluent families to be more stable than poor ones, especially if the children could inherit the parental resources or territory. Children from wealthy families are expected to be extra picky about when and under what circumstances they leave home.
By remaining, mature children may inherit the money, implying that wealthier families should be more stable over time than impoverished families. Offspring of several species of family birds and animals occasionally inherit their parents' breeding status. Davis and Daly (1997) give empirical evidence for this hypothesis by discovering that high-income families are more likely than low-income households to retain social links with their extended family.
Assistance with child raising will be more common in families than in comparable groups lacking family relations. For example, a sister or brother may help raise a younger sibling, offering a significant inclusive fitness advantage by staying with the family. This prediction is easily testable in people.
Sexual aggressiveness will be lower in families than in non-related groups because relatives will develop to minimise the hazards associated with inbreeding. Sexual desire between siblings, as well as conflict between father and son for sexual access to the mother, will be uncommon. Individuals can escape the costs of mate guarding due to lower sexual rivalry within families.
While family members have several opportunities for sexual interaction, incestuous matings among birds and mammals are relatively rare. Mating was virtually always exogamous—with birds outside the family—in eighteen of the nineteen avian species investigated in this respect. Incest between genetic relatives is uncommon in humans, but it is significantly more prevalent between stepfathers and stepdaughters.
He identifies two sorts of families −
Simple families, in which only one female reproduces (e.g., a mother and her pre-reproductive kids), and
Extended families, in which two or more relatives of the same sex can reproduce. The presence of a breeding male is not required to define a family. When the father is present, the family is referred to as biparental since the mother and the father share specific parental responsibilities.
The family is called matrilineal when the man is gone since the female is in charge of parenting. One distinguishing trait of all families is that kids live with their parents once they reach reproductive age. An identical situation may develop among humans if a parent dies and leaves a significant bequest. Children file lawsuits claiming inheritance, while claims made by genetically unrelated persons (e.g., a father's love to whom he bequeathed wealth) are frequently disputed.
Sexual aggressiveness will grow if an existing breeder is lost and replaced by a breeder genetically unrelated to current family members. When a mother gets divorced, widowed, or abandoned and remarries an unrelated guy, her severe aversion to incest is alleviated. Stepfathers may be sexually attracted to stepdaughters, placing mother and daughter in an intrasexual conflict.
Aggression between sons and stepfathers is typical in several bird species, as these unrelated males are now sexual rivals. Having a stepfather in the household puts prepubescent and postpubescent females at a higher risk of sexual abuse in humans.
Jennifer Davis and Martin Daly, evolutionary psychologists, have critiqued Emlen's theory, proposing some beneficial revisions and empirical testing of a few significant predictions. Davis and Daly present three broad concepts that give a unique foundation for examining human families −
Human families may stay together due to competition from other groups, such that remaining in a sizeable kin-based coalition is advantageous in such group-on-group competition
Humans engage in extensive social exchange with nonkin based on reciprocal altruism.
Non-reproductive helpers, such as postmenopausal women, have little incentive to encourage their offspring to disperse, which may help to stabilise families.
These three factors may impact the logic of Emlen's forecasts. Consider prediction 1, which states that families will disintegrate when suitable breeding opportunities become available elsewhere. If a woman is postmenopausal and unable to reproduce, it would be detrimental for her to forsake her family and the assistance she might offer if a breeding vacancy appeared elsewhere. She cannot take advantage of the breeding opportunity since she is postmenopausal. It would be more advantageous for her to stay with her family and continue to assist them. Human women's relatively early menopause may thus be a unique feature influencing the evolution of human families.
Emlen's family theory combines ecological limitations and family benefit models to explain the evolution of families. Emlen's Theory makes four predictions about the family dynamics of kinship and cooperation −
Families will emerge when there are enough reproductive openings,
Disband when vacancies become available,
Families with considerable resources will be more stable and long-lasting,
Assistance with child raising will be more common,
Sexual aggressiveness will be lower in families than in non-related groups,
The sexual desire between siblings will be uncommon, and
Incestuous matings among birds and mammals are rare.
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