What can evolutionary biology tell us about male-female disparities in family preferences? Could mothers be more concerned about their children than fathers, for example? Gender inequalities have been observed in the economics literature—children gain more from money placed in the hands of mothers rather than fathers, for example—and these variations are assumed partly due to preferences.
However, family economics is primarily concerned with how prices and incomes affect behaviour in the context of exogenous choices. This approach is supplemented by evolutionary biology, which treats preferences as the result of natural selection. We study the extensive biological literature for evidence of the evolutionary underpinnings of parental choices.
We look at essential traits—sex variations in gamete size and internal fertilization—and explain how they have been assumed to cause male-female differences in altruism towards offspring and other family behaviour preferences. The evolutionary approach to the family reveals links between topics traditionally assumed to be unique in family economics, such as parental care.
The biological basis of human paternal care research is heavily influenced by two historical precedents: studies of maternal behaviour in mammals and paternal behaviour in birds. The fast initiation of mammalian maternal behaviour after parturition has been linked to elevated levels of numerous hormones. These hormones interact with neurotransmitter systems, specifically dopamine, to alter how new mothers perceive the attractiveness and rewarding characteristics of contact with their children.
Extending the animal study to human mothers gives us hope that results on paternal behaviour in mammals will inform research on human fathers. Maternal care is the traditional style of parental care in mammals, as evidenced by the shared specialized reproductive architecture and physiology, with paternal care having numerous origins in a few species. Male birds have high testosterone levels during the wooing period of breeding, which then drops throughout incubation and chick raising.
Testosterone influences the tradeoff between mating and parental behaviour in birds: males feed their young less frequently when testosterone levels are experimentally boosted. Despite the traditional negative association between testosterone and paternal care, environmental stressors, such as polyandrous birds, might cause a divergence between ancestral hormone levels and typical male behaviour.
Compared to maternal behaviour, the biological foundation of mammalian paternal behaviour has received far less attention. When research on naturally paternal species revealed hormonal responses identical to those seen in mothers, attitudes began to shift. Prolactin, a hormone involved in milk production and parental behaviour, was higher in male marmosets carrying newborns than in males not carrying infants.
Additionally, fathers in California mice had greater Prolactin levels than non-fathers. These and other research revealed a biological basis for paternal behaviour in naturally paternal species, which may also exist in human fathers.
A massive amount of cross-cultural research on people, using metrics ranging from time spent in proximity to time spent caressing to time spent instructing, demonstrates that women care for their children more intensely than males. The intriguing question is; why do moms outnumber fathers? Several explanations have been suggested to explain why female parental care is so prevalent. We shall look at two of the most important to humans −
The paternity uncertainty theory and
The mating opportunity costs hypothesis.
Mothers in the animal kingdom are generally "certain" of their genetic contribution to their kids. Men can never be "certain." The dilemma of paternity uncertainty means that there is always some chance that another male fertilized the female's eggs from a male perspective.
Paternity ambiguity is most significant in animals that use internal female fertilization, which includes many insects, humans, all primates, and all mammals. Because of internal female fertilization, when a male appears, the female may have already mated with another male, and her eggs may be fertilized. She could mate with another guy at any time throughout their relationship, possibly in secret.
Paternity uncertainty is insufficient to prevent the emergence of paternal concern. Nonetheless, it makes it less profitable for fathers to invest in their children when compared to moms. With paternity doubt, each unit of parental investment pays off more for mothers than fathers because some of the "father's" effort will be wasted on progeny that is not his own.
A second hypothesis stems from sex differences in mating opportunity costs. Mating opportunity costs are missed additional mating due to effort devoted to offspring. Females and males both suffer mating opportunity costs. While a mother is gestating or breastfeeding her child or a father is fending off predators, neither has a high probability of securing additional mates.
The mating opportunity costs are higher for males than females; for this reason, males' reproductive success tends to be limited primarily by the number of fertile females they can successfully inseminate. In humans, for example, males can produce more children by mating with various women, but women generally cannot increase reproductive output directly by mating with various men. In summary, because the mating opportunity costs of parental care will generally be higher for males than females, males will be less likely than females to take on parental care.
Mothers' parental involvement begins long before birth. Throughout the 9-month gestational period, the mother's resources supply nutrition and a safe environment for the developing kid. Although this appears to be a pleasant connection with the mother and foetus having the same goals at first look, the genetic interests of both parties are not similar.
Because the developing foetus is more closely related to itself than to its mother or any future siblings, pregnancy becomes a delicate balance between the developing foetus' tendency to secure as large a share of maternal resources as possible and the mother's tendency to preserve some resources for herself and future offspring. This balancing act frequently results in several unpleasant symptoms for the mother and serious problems.
Researchers examined pregnancy difficulties from the standpoint of maternal-fetus conflict, implying that such conflicts are to blame for several perplexing elements of pregnancy and its consequences.
Competition occurs even in personal interactions, such as between a mother and her unborn child. Women should be particularly cautious about which pregnancies are carried to term and whose babies evoke parental investment because of women's high degree of parental investment. Because it entails a parent murdering the vehicle responsible for spreading his or her genes, infanticide appears to be utterly incompatible with evolutionary theory.
Nonetheless, given the high level of human maternal commitment, a mother should relinquish a nonviable kid as soon as feasible. We would expect to witness infanticide if the expense of continuous investment exceeded the expected payoff of a reproductively capable adult. She reviewed cross-cultural evidence from 60 civilizations worldwide, documenting the causes cited for infanticide. These include characteristics of baby quality (deformity or prenatal sickness), number (twins), or timing (when a newborn is delivered too soon after a previous birth, the mother favours the kid in whom she has previously invested, following evolutionary predictions).
Economic factors can have a role. Infanticide was recognised as a response to a lack of male support and economic hardship in 56 civilizations. A kid born from a secret adulterous connection also jeopardises her husband's ability to provide for her elder children. Infanticide rates decrease as the mother's age increases, as does reproductive value. Although abortion has successfully eliminated the necessity for infanticide in many societies, its correlates are similar to those of infanticide: maternal youth, the absence of a supportive male partner, or paternity ambiguity.
In contrast, after a mother has dedicated herself to an infant, we would expect her to struggle to safeguard it. Although maternal hostility has been extensively researched in rodents, it has received less attention in humans. However, it is an essential domain where evolutionary theory might create theories.
Males play a function in securing a connection with the offspring by making an offspring's decisions while involved in a home. The enormous evolutionary distinctions between direct and indirect care provided by mothers and fathers are thus neglected, and both parents affect the offspring's life decisions. Various parenting practices influence a child's disposition across cultures.
Furthermore, different attachment styles can influence an offspring's development, future mate choices and parenting skills. Such parental factors give rise to notions of inclusive fitness and investment in explaining the foundations of parenting practices passed down to kids, such as to secure the parents' reproductive success.
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