PARENTAL INVESTMENT THEORY
THE DIFFERENCE BETWEEN SEXUAL SELECTION THEORY AND PARENTAL INVESTMENT THEORY
Sexual selection theory and parental investment theory are not the same, but they are related concepts within the broader field of evolutionary biology. Both theories explain mating behaviours and strategies in the context of evolutionary biology; sexual selection theory primarily focuses on the evolution of traits favourable for attracting and competing for mates. In contrast, parental investment theory focuses on the implications of the relative parental contributions of each sex to their offspring.
SEX DIFFERENCES IN PARENTAL INVESTMENT.
Please note Parental investment and sexual selection overlap. Many research studies used for Sexual selection can also be used for parental investment.
In evolutionary terms, humans are vehicles for ensuring the continued existence of the genes they contain. They do this through sexual reproduction: the greater the number of offspring a human being produces, the greater the probability that any genes it contains will continue to exist and the greater the probability that at least some of the offspring will produce offspring of their own.
Success, therefore, comes from producing as many offspring as possible that will produce their offspring. Merely producing many offspring is no guarantee that some will survive; human babies require parental investment in food, shelter, protection from predators, education, etc., to ensure that they survive to sexual maturity and can pass on their parent’s genes to future generations. Humans are born in a relatively undeveloped state compared to many other species. This condition is known as altriciality. Human infants depend entirely on their caregivers, usually their parents, for care, protection, and nourishment. They lack the physical and cognitive abilities necessary for independent survival.
This dependence on parental care is fundamental to human biology and behaviour. But there is a tradeoff between energy spent reproducing and energy spent investing; energy spent investing cannot be used for reproduction, and energy spent reproducing cannot be invested.
Evolutionary explanations of parental investment concern the conflicts over the amount provided. These conflicts can occur between parents (which sex invests more) and between parents and offspring (how much investment each offspring gets compared with its siblings). Only parental investment will be discussed in this account, concentrating on sex differences.
Despite aspects of the human EEA differing from most present human environments, for example, we know that population densities were much lower than today, that most societies were very probably family/kin-based, and that child mortality rates were very probably much higher than today. However, humans still took more than a dozen years to reach sexual maturity, and fathers were less certain of paternity than mothers were of maternity (as they are today, absent a genetic test). These latter facts form the foundation for considerable research into differential parental investment. Human offspring require enormous investment to reach sexual maturity. If half of one's children were likely to die, parents needed to be able to target their investment towards the healthiest, most viable offspring. Similarly, males should have targeted their investment at offspring that were likely to be their own. These hypotheses have found considerable support among humans and other animals.
Parental Investment Theory, developed by Robert Trivers in 1972, is a fundamental concept in evolutionary psychology and biology. It explains how and why different sexes invest different amounts of time, energy, and resources in their offspring. The theory revolves around several key principles:
Differential Reproductive Investment: Trivers proposed that in species where one sex (typically females) invests more heavily in the reproductive process, they will be more selective in choosing mates. This is because they have more to lose if the reproductive endeavour fails. In contrast, the sex that invests less (typically males) will compete for access to the higher-investing sex.
Anisogamy: Trivers highlighted the fundamental difference in gamete size between males and females. In most species, females produce larger, energetically costly eggs, while males produce smaller, more numerous sperm. This asymmetry in gamete size contributes to differences in reproductive investment.
Parental Care: Trivers recognised that investment in offspring can continue through parental care after mating. In species where parental care is essential for offspring survival, the sex that invests more in care (often the female) will be choosier when selecting mates.
Variability in Reproductive Rate: Trivers noted that because females typically invest more in each offspring, their reproductive rate is generally lower than that of males. With their lower investment per offspring, males can reproduce faster, leading to competition for access to mates.
Sexual Selection: Parental Investment Theory helps explain the evolution of sexual selection. In species where females invest more, males often engage in competitive behaviours to gain mate access. This competition can lead to the evolution of traits and behaviours that enhance a male's ability to secure mates, such as elaborate displays or physical weaponry.
Mate Preferences: Trivers' theory predicts that females, as the higher-investing sex, should be more selective when choosing mates. They should prioritise traits or behaviours that indicate good genetic quality, resources, or commitment to parental care. In contrast, males may be less selective and prefer mates based on fertility and reproductive potential indicators.
FEMALES HAVE ALREADY INVESTED THE MOST (ANISOGAMY)
Females typically contribute more to the physical development of their offspring due to anisogamy, which is the significant difference in the size of sex cells (eggs and sperm). This difference results in eggs being more costly to produce than sperm. In the case of humans, this means that females bear the burden of nine months of gestation and subsequent lactation, providing the majority of the energy required for their infants' growth from conception to the age when they can be weaned onto other food. Consequently, if offspring do not survive due to a lack of care, their substantial investment is more costly for females.
Due to this discrepancy in the cost of reproduction, females tend to be more selective in choosing mates, while males compete for mating opportunities, as Trivers (1972) proposed. In other words, females are generally less promiscuous than males and take their time selecting a mate. They seek to ensure that their offspring inherit high-quality genes and have access to ample resources, thus ensuring their offspring's fitness.
For males, the optimal strategy is to invest their efforts primarily in reproduction, given that sperm production is relatively inexpensive compared to the substantial investment made by females. This leads to a division of reproductive labour where females are choosier in mate selection and often take on more parental care responsibilities. At the same time, males focus on maximizing their reproductive opportunities.
CONCEALED OVULATION AND OESTRUS
Oestrus is a behavioural and physical change in which a female becomes attractive to males and receptive to sexual advances. Among most species of animals, females are not continually open or able to have sexual intercourse. Their ovulation is limited to a few times a year and is commonly referred to as being in ‘heat’ or ‘season’.
In most species, the hormonal changes associated with oestrus (or heat) trigger biological signals that alert the male that a female is ovulating and is ready to mate. These signals can be blood flow from the vagina, patches of special skin around the vulva and anus that become a noticeable pink or burgundy colour as they swell up (known as estrus swellings) and smell. This does not happen in humans. Ovulation is concealed, and there is no oestrus. This benefits human females as they can offer sex all the time. Their partner is, therefore, likely to stay with them and not look for sex elsewhere when they are not ovulating. This means the female is likely to get resources and protection continually. The downside of concealed ovulation is that the male is unsure if he is impregnating the female when he has sex with her, as she may not be ovulating. Moreover, he can not be certain of paternity if he does not know when his partner is ovulating because he cannot be certain she has been impregnated by someone else.
SEX DIFFERENCES IN INVESTMENT FEMALES
Eggs are more costly to produce than sperm, as they are bigger.
Limited eggs released per lifetime, approximately 400
Depending on the culture, a limited number of possible pregnancies/children per lifetime, e.g., 1-20.
Time limit on fertility /egg release, e.g., females go through menopause and become infertile in middle age.
Nine months of pregnancy, which is energy-consuming and physically limiting. It makes Mothers vulnerable, as she is not so mobile and self-sufficient/independent. A recent study published in Science Advances suggests that pregnancy is an extremely physically demanding process, akin to running a 40-week marathon. Researchers examined elite athletes' basal metabolic rates (BMR) in demanding races like Ironman and the Tour de France. They found that the most an individual can sustain in terms of calorie burn is about 2.5 times their BMR, roughly 4,000 calories a day for the average adult. Pregnant women, on the other hand, operate at approximately 2.2 times their BMR, almost at the maximum sustainable level, for around 270 days. Going beyond this rate would be unsustainable, potentially harmful to the body, and even life-threatening.
Breastfeeding: time-consuming, energy consuming and means the mother is not independent.
Female brains are generally wired differently. They have less testosterone and more empathy, which makes them more likely to attach to their infants immediately. Oxytocin released during breastfeeding also increases attachment behaviour.
Childbirth is painful, long, hazardous and can be life-threatening. The SDG target for maternal deaths is for a global maternal mortality ratio (MMR) of less than 70 maternal deaths per 100,000 live births by 2030. The global MMR in 2020 was estimated at 223 maternal deaths per 100,000 live births, down from 227 in 2015 and 339 in 2000.
Hemorrhage.
Hypertensive disorders (e.g., preeclampsia and eclampsia)
Infections (including sepsis)
Unsafe abortion
Obstructed labour
Pre-existing medical conditions (e.g., diabetes, heart disease, HIV)
Lack of access to healthcare
Anemia
Postpartum complications
Socioeconomic factors (e.g., poverty, lack of education, gender inequalities)
SEX DIFFERENCES IN INVESTMENT MALES
Approximately 300,000,000 – 400,000,000 sperm per ejaculation.
Unlimited sperm per lifetime.
Unlimited number of possible children per lifetime. All males have to do is find a willing and ovulating partner.
No time limit on fertility. Men can produce sperm until they die and well into old age.
Getting a woman pregnant requires little energy! It is estimated that the energy required is equivalent to boiling a kettle.
No breastfeeding, but the Father may invest resources.
Male brains are, on the whole, wired differently. They have more testosterone and less empathy, making them less likely to attach to their infants.
SUPPORTING RESEARCH FOR PARENTAL INVESTMENT THEORY
IMPLICATIONS
If Parental Investment Theory is considered a scientifically valid framework, the evidence must revolve around several key statements that align with its core principles.
Here's how these statements align with the theory:
MALES WILL HAVE A HIGHER SEX DRIVE: While not directly stated in the theory, it's implied that males might exhibit a stronger sex drive due to the potential benefits of maximising their reproductive opportunities.
MALES WILL WANT TO HAVE SEX WITH AS MANY DIFFERENT FEMALES AS POSSIBLE BECAUSE THEY HAVE A LOT OF SPERM AND NO COMMITMENT. This aligns with the idea that males may be more inclined toward short-term mating strategies, seeking multiple sexual partners.
FEMALES WILL BE LESS PROMISCUOUS: The theory suggests that females may be choosier in selecting mates due to their higher investment in offspring, which could translate into less promiscuous.
MALES WILL BE MORE SEXUALLY JEALOUS AS THEY ARE UNCERTAIN OF PATERNITY: This aligns with the concept of paternity uncertainty, which may lead to heightened sexual jealousy in males to ensure their genetic lineage.
MALES WILL NOT INVEST IN STEPCHILDREN: This is consistent with the idea that males may prioritize investment in their biological offspring to maximize their genetic success, potentially leading to reduced investment in stepchildren.
FEMALES WILL BE MORE EMOTIONALLY JEALOUS, FEARING THAT THEIR PARTNER WILL FALL IN LOVE WITH SOMEONE ELSE: While not explicitly part of the theory, the idea that females may be more emotionally invested in their relationships aligns with the concept of females seeking long-term partners who can provide support and resources for their offspring.
RESEARCH ON MALE PROMISCUITY: MALES WANT MORE SEX
SHORT TERM MATING STRATEGIES
Gangestad and Simpson (2000) conducted a comprehensive study on the evolution of human mating strategies. They found evidence supporting males' tendency to engage in short-term mating strategies, seeking multiple sexual partners. Their research suggests this behaviour may be linked to evolutionary factors such as maximising reproductive opportunities.
Schmitt (2005) conducted a cross-cultural study on sociosexuality, which refers to the willingness to engage in sexual activity outside of a committed relationship. The findings of this study indicate that males, across various cultures, tend to exhibit a more unrestricted sociosexual orientation.
MATE PREFERENCE
Buss (1989) conducted a study in 37 different cultures to explore sex differences in mate preferences. The research revealed that males, on average, emphasise characteristics related to physical attractiveness and youth in potential mates.
Singh (1993) investigated the role of the waist-to-hip ratio (WHR) in mate preferences. His research found that males across different cultures tend to be attracted to females with a specific WHR associated with reproductive health and fertility.
Clark and Hatfield (1989): In this classic study, male and female confederates approached individuals of the opposite sex on a college campus and asked if they would be interested in going on a date, having a casual sexual encounter, or going to bed with them. The study found that men were more likely to agree to the proposition of casual sex compared to women.
Mark. et al. (2011): Mark and colleagues researched sociosexuality, which measures the willingness to engage in sexual activity without commitment. Their study found that men generally reported a higher sociosexual orientation score than women, indicating a greater inclination toward short-term mating strategies involving multiple sexual partners.
Conley et al. (2011): This study investigated motivations for engaging in casual sex among college students. It found that men were more likely to report motivations related to physical pleasure and novelty-seeking,
SEX DRIVE
Testosterone, a hormone predominantly found in higher levels in males, is associated with increased sex drive. Numerous studies have established a positive correlation between testosterone levels and sexual desire in men.
The study by Vi Nguyen and colleagues on October 28, 2022, looked at factors governing sexual desire, encompassing neuroendocrine regulations, psychological facets, and sociocultural influences. A plethora of evidence from animal and human studies substantiated this assertion. Functional neuroimaging studies showed specific brain regions activated by sexual stimuli under the influence of androgenic pathways. A recurring finding in this review was the robust correlation observed between serum testosterone levels and libido in men, a relationship firmly established through rigorous research endeavours. Significantly, the research highlighted the practical applicability of this association, particularly in the context of testosterone replacement therapy, where it played a pivotal role in enhancing sexual desire among hypogonadal men.
According to research by Chapman University, which reviewed the sex lives of over 52,500 people, the group most likely to always have an orgasm is heterosexual men at 95%. Only 65% of heterosexual women say they usually or always have an orgasm, which was the lowest of all demographics included.
Van Anders, S. M., Goldey, K. L., & Kuo, P. X. (2011). The Steroid/Peptide Theory of Social Bonds: Integrating Testosterone and Peptide Responses for Classifying Social Behavioral Contexts. Psychoneuroendocrinology, 36(9), 1265-1275.
Roney, J. R., Mahler, S. V., & Maestripieri, D. (2003). Behavioural and hormonal responses of men to brief interactions with women. Evolution and Human Behavior, 24(6), 365-375.
These studies provide empirical evidence that supports the theory that males have a greater inclination toward short-term mating strategies, which can involve seeking multiple sexual partners due to their evolutionary drive to maximise reproductive opportunities.
CHASTITY: MALES PREFER CHASTE WOMEN:
The evidence supporting the idea that men prefer chaste women as part of sexual selection theory primarily comes from studies in evolutionary psychology and related fields. .
Here are some key sources of evidence:
Buss, D. M. (1989). "Sex Differences in Human Mate Preferences: Evolutionary Hypotheses Tested in 37 Cultures": This landmark study by David Buss examined mate preferences across 37 cultures and found that men generally placed more excellent value on chastity than women did. This study is often cited in discussions about evolutionary psychology and sexual selection.
Schmitt, D. P. (2003). "Universal Sex Differences in the Desire for Sexual Variety: Tests From 52 Nations, 6 Continents, and 13 Islands": In this extensive study, David Schmitt explored sexual behaviours and attitudes across different cultures. The findings suggested that men typically show a higher desire for multiple partners, which could indirectly suggest a preference for chastity in long-term mates as a way to ensure paternity.
Greiling, H., & Buss, D. M. (2000). "Women’s Sexual Strategies: The Evolution of Long-Term Bonds and Extrapair Sex": This study examined women's sexual strategies from an evolutionary perspective and discussed how these strategies might influence men's preferences, including the preference for chastity as a means to ensure paternity certainty.
Apostolou, M. (2007). "Sexual Selection Under Parental Choice: The Role of Parents in the Evolution of Human Mating": This study explores the role of parental choice in human mating and discusses how preferences for traits like chastity may have evolved not only through individual choice but also through parental influence in mate selection.
Gangestad, S. W., & Simpson, J. A. (2000). "The Evolution of Human Mating: Trade-Offs and Strategic Pluralism": This paper discusses the evolution of human mating strategies and how men's preferences, including for chastity, can be understood in the context of these strategies.
Shackelford et al. (2005) investigated mate preferences and attitudes towards promiscuity in potential partners. Findings: The research showed that men place a high value on sexual fidelity in long-term mates, considering promiscuity as undesirable. A study conducted by Clark and Hatfield examined gender differences in responses to sexual propositions from strangers. The researchers conducted a college campus field study using a simple methodology. Male and female research assistants approached strangers of the opposite sex and asked one of three questions:
"Would you go out tonight with me?"
"Would you come over to my apartment tonight?"
"Would you go to bed with me tonight?"
The responses were recorded, and the study aimed to assess gender differences in receptivity to these sexual propositions. The study showed significant gender differences: When asked if they would go out tonight, both men and women showed relatively high levels of receptivity, with men being slightly more receptive. Women overwhelmingly declined when asked to come over to an apartment or go to bed together, while men were much more receptive to these propositions. These findings have been widely discussed and cited in the literature on human sexuality and mate selection. The study is often used to illustrate gender differences in sexual behaviour, with men generally being more willing to engage in casual sexual encounters with strangers compared to women.
Analysing cross-cultural and historical attitudes toward women adds credibility to this aspect of evolutionary psychology. In numerous societies, women face severe consequences if they are perceived as unfaithful. For instance, countries like Iran, Nigeria, Saudi Arabia, and Indonesia have been reported to employ extreme measures such as stoning unfaithful women to death (Guardian, 2005).
The use of derogatory terms to describe women who are perceived as promiscuous or flirtatious, including words like "whore," "slag," "slut," "sket," "bike," "tramp," "ho," "tart," and others, is widespread in many cultures. Notably, there is a lack of comparable derogatory terms for males in these contexts. This discrepancy highlights the existence of double standards and societal pressures related to female promiscuity, where women are often judged and stigmatised for behaviour that may not receive the same level of criticism or condemnation as men.
Additionally, sex surveys often reveal that women tend to underreport the number of sexual partners they have had, indicating societal pressures related to female promiscuity. For example, A study by T.W. Smith examines discrepancies between men and women in reporting the number of opposite-gender sexual partners in national surveys from four countries: the United States, Canada, Great Britain, and Norway. The research finds that men consistently report more female partners than women report male partners. These reports' ratios vary but tend to increase as the reference period becomes longer. The study suggested that intentional misreporting is the most likely explanation for these discrepancies, with men tending to overreport and women tending to underreport.
VIRGINITY CHECKS: The examination of brides for signs of virginity after the first night of marital sex. In some cultures, there is a tradition of conducting virginity examinations on brides after their first night of marital sex. These examinations are intended to confirm the bride's virginity and, by extension, her fidelity to her husband. Failure to pass such an examination can lead to social stigma, divorce, or even violence against the bride.
USE OF VEILS, HIJABS, WIGS, SCARVES, AND WEARING WHITE:
The shift towards white wedding gowns as a symbol of prosperity, virginity, and lifelong commitment was notable during the mid-20th century and continued through the end of the 20th century in many Western cultures.
The wearing of veils, hijabs, and burqas can be linked to societal norms that dictate modesty and restrict the visibility of women's bodies and faces.These coverings are often associated with religious and cultural practices that aim to prevent the sexual objectification of women and limit their interactions with men outside their families. Such practices are rooted in notions of protecting women from unwanted male attention and preserving their fidelity.
FEMALE CIRCUMCISION (GENITAL MUTILATION)
Female circumcision is practised in some cultures as a means to control female sexuality by reducing sexual pleasure and desire. It is often justified by the belief that it will help maintain a woman's chastity before marriage and fidelity within marriage. The practice is rooted in gender inequality and the desire to ensure women's sexual compliance.
THE MAGDALENE LAUNDRIES
The Magdalene asylums were institutions that existed from the 18th century until the mid-20th century and were primarily intended for women referred to as "fallen women," a term often associated with sexual promiscuity. These asylums were established in various countries, including Europe, Britain, Ireland, Canada, and the United States, and their mission evolved. Initially, these asylums aimed to rehabilitate women and reintegrate them into society. However, as the 20th century approached, the institutions became increasingly punitive and prison-like in their approach. Inmates were subjected to rigorous physical labour, daily prayer, and enforced silence. In Ireland, such institutions were known as Magdalene laundries, and it's estimated that approximately 30,000 women passed through these laundries. The last Magdalene asylum in Ireland closed on September 25, 1996.
The phenomenon extended beyond women involved in prostitution to include unmarried mothers, mentally challenged women, and abused girls. Even young girls who were deemed too promiscuous, flirtatious, or attractive by their families were sometimes sent to these asylums. In many cases, women were admitted to these institutions at the request of family members, mostly male relatives. Without external support or someone to vouch for them, many of these individuals remained in the asylums for the rest of their lives, with some even taking religious vows.
These asylums and their practices were not unique to one particular region. Still, they were part of a broader societal phenomenon in the 19th and early 20th centuries, where individuals considered to have "social dysfunction" were committed to various institutions. With their complex history, the Magdalene asylums serve as a poignant reminder of the social norms and attitudes of the times in which they operated.
SEX POSITIVITY AS A CRITIQUE
A shift in contemporary dating and sexual behaviour challenges traditional expectations rooted in evolutionary psychology theories. Studies reveal that over 25 per cent of women engage in sexual activity within the first week of dating someone, marking a departure from historical norms of waiting longer. Previously, men were often expected to court and invest time and resources in women for sexual gratification. However, modern dating dynamics indicate significant changes.
Several factors contribute to this shift. Gender equality in the workplace and women's financial independence have reshaped traditional gender roles and behaviours. Additionally, the widespread availability of contraceptives like the Pill has empowered women with greater control over their reproductive choices.
Internet pornography's influence is also noteworthy, as it has broadened access to diverse sexual experiences, including for women. This desensitization to the once-sacred nature of sexual relationships within marriages may contribute to changing dynamics.
Some evolutionary psychology theorists suggest underlying evolutionary reasons for these changes. They propose that women engaging in short-term mating strategies can derive benefits, including access to high-quality genes not available from long-term mates. Short-term mating can also provide women with protection and provisioning for themselves and their offspring, particularly in cultures practising partible paternity.
In this context, short-term mating can serve to achieve long-term mating goals. Women pursuing short-term mating strategies tend to be discerning about the mate value qualities of their brief sexual partners. They often prefer individuals exhibiting physical symmetry, facial masculinity, and other cues associated with high testosterone levels, as proposed by Gangestad and Simpson in their research. This selectivity aligns with the notion that women seek advantageous traits even in short-term partners for potential genetic and resource-related benefits.
IMPACT OF INTERNET PORNOGRAPHY:
Research by Peter and Valkenburg (2006, 2007) found that exposure to online pornography was associated with more permissive sexual attitudes, including greater acceptance of promiscuity and casual sex. They observed that frequent exposure to Internet pornography was linked to desensitisation to sexual content and increased acceptance of non-traditional sexual behaviours.
SEX POSITIVITY AND CHANGING ATTITUDES:
Fahs and Swank's (2013) study highlighted how sex-positive feminism challenges traditional views on sexuality, including the devaluation of chastity. They found that embracing sex positivity led to greater acceptance of diverse sexual expressions and reduced stigma around non-traditional sexual behaviours.
DIGITAL PLATFORMS AND SEXUAL ATTITUDES:
Ongoing research on platforms like OnlyFans explores how they shape public perceptions of sexuality. Initial findings suggest that these platforms contribute to a more open and diverse understanding of sexual expression by normalising the monetisation of sexual content and challenging traditional taboos.
GENDER IDEOLOGY AND SEXUAL PREFERENCES:
Studies by Sakaluk et al. (2014) investigated how changing gender ideologies impact mate preferences. Findings indicated that shifts towards gender equality led to a reevaluation of traditional gender roles and preferences, with individuals placing less emphasis on traits associated with traditional gender roles, such as chastity.
CULTURAL AND SOCIETAL SHIFTS:
Cross-cultural research by Schmitt (2005) revealed variability in the importance of chastity across different cultures. The study showed that cultures with more traditional values tend to prioritise chastity in potential mates, while cultures with greater gender equality may place less emphasis on this trait.
GENERATIONAL CHANGES IN ATTITUDES:
Studies by Twenge et al. (2015) found generational shifts in sexual attitudes and behaviours, with younger generations displaying more permissive attitudes towards sex and relationships.
These changes were attributed to factors such as increased exposure to sexual content in media, greater acceptance of diverse sexual orientations, and changing social norms regarding sexual behaviours. These cultural and historical analyses provide intriguing perspectives on the development of women's honour over time. However, providing direct evidence that aspects of sexual selection theory directly account for historical instances of valuing female chastity poses challenges. This is due to the theory's retrospective nature, whereby all associated data is correlational and derived from past events. Furthermore, the theory's unfalsifiable nature, designed to explain outcomes post hoc, complicates efforts to validate its validity.
PSYCHIATRIC PROBLEMS RELATED TO FERTILITY
Statistics indicate a stark contrast in seeking psychiatric treatment related to infertility between genders, with 37% of women seeking help compared to only 1% of men. Conversely, when it comes to sexual dysfunction, more men than women seek medical assistance. This can be understood from an evolutionary perspective. In ancestral contexts, women heavily invested in reproduction due to gestation and lactation, making infertility a significant threat to their reproductive success. Conversely, men prioritized quantity in offspring, which might explain their lower concern about infertility. However, sexual dysfunction directly impacts men's mating and procreation abilities, leading to a higher rate of seeking medical help among them.
CONJUGAL ROLES AS A CRITIQUE
The study by Daly and Wilson (1978) suggests that males may allocate most of their time and effort to courtship to maximize reproduction, potentially leaving less time for parental investment. However, there are several factors and counterarguments to consider:
Increased Male Involvement in Parental Care: Current sociological statistics indicate that male involvement in childcare and housework has increased significantly in recent decades. However, it is still nowhere near female involvement. This suggests that many fathers do invest in their children and contribute to parenting responsibilities.
Social vs. Biological Factors: Some researchers argue that men's perceived lack of commitment may be influenced more by social factors than biological ones. For instance, media portrayals and cultural influences, such as male-focused magazines encouraging promiscuity, can shape attitudes and behaviours related to commitment in relationships.
Research by Geher: Geher conducted a study involving graduates from the State University of New York to explore perceptions of parental investment. The study found no significant gender differences in how participants saw themselves as future parents. However, when assessing parental investment levels (e.g., willingness to cancel work appointments for a sick child), males exhibited higher autonomic nervous system (ANS) arousal. This physiological response could be interpreted as suggesting that men's actual parental investment might be lower than their self-perceived investment.
Critique: It's important to consider the limitations of Geher's study, such as the sample comprising students with no parenting experience. Therefore, the findings may not be generalisable to actual parents. Additionally, the study's sample consisted of American students, limiting the generalisability of the results to individuals from diverse cultural backgrounds.
In summary, the issue of male commitment and parental investment is complex and influenced by a combination of biological, social, and cultural factors. While some research suggests that men may allocate more time to courtship, modern societal changes and evolving gender roles have led to increased male involvement in parenting. Understanding the interplay of these factors is essential for a comprehensive understanding of parental investment and commitment.
MALES WILL BE MORE SEXUALLY JEALOUS AS THEY ARE UNCERTAIN OF PATERNITY:
Evolutionary psychologists propose that there is a clear link between jealousy and violence, particularly in males. They argue that males may resort to violence as a means to achieve exclusive sexual access to their female partners.
This drive for sexual exclusivity is said to have evolved due to the reality of paternity uncertainty for males. Unlike females, males cannot be certain that they are not investing their efforts and resources in raising another man's child. From an evolutionary perspective, the only reproductive success that counts is passing on one's genetic material.
Jealousy is considered to have evolutionary significance because it mobilizes males to protect the propagation of their genes. In this context, violence may be seen as a way to coerce fidelity and punish infidelity (Daly & Wilson, 1988; Buss, 1994).
According to this perspective, female jealousy would be directed toward ensuring continued access to the resources provided by the male, both for themselves and their offspring. This is thought to manifest in men's focus on sexual fidelity and women's greater concern with emotional attachment and relationship security (Buss, 1994).
SEXUAL JEALOUSY
Experimental evidence has demonstrated higher levels of jealousy among males in laboratory settings.
In a study conducted by Wilson, both males and females were instructed to envision their partner in a scenario involving sexual infidelity. The results revealed that males were significantly more likely to exhibit a stronger galvanic skin response, an indicator of a stress response, compared to females. This suggests that males tend to experience more intense feelings of jealousy when confronted with the idea of their partner's sexual infidelity.
In the study by Wilson, it should be noted that the quasi-experimental design used may not establish cause and effect conclusively. Additionally, ethical considerations in research should be considered, especially when questions are personal and potentially embarrassing for participants. The observed stress responses in men could be attributed to personal discomfort or a sense of male pride being affected.
The study on sexual jealousy by David M. Buss discusses various aspects of human mating strategies and sexual jealousy. Buss proposes that sexual jealousy tends to be more pronounced in males than females due to this observed phenomenon. Buss, D. M. (1992).
Buss et al. (1992) investigated differences in emotional responses to sexual and emotional infidelity between men and women. Findings: The study found that men reported greater distress in response to sexual infidelity by their partners compared to emotional infidelity,
Manipulation in close relationships: Five personality factors in interactional context. Psychological Science, 3(6), 346-351.
In a Canadian study covering over a thousand spousal homicides, 20% were attributed to jealousy, with men being the killer in 195 instances compared to 19 for women.
Gibbens (1958), in his study of 195 homicide cases, reported that jealousy was the prime motivation in 22% of the killings. I
in Wolfgang's (1958) study of 588 homicides and West's (1968) study, jealousy was the third most common motivation.
In a more detailed study of homicide in Detroit, jealousy emerged as the leading cause of domestic killing. In contrast, among the male killers, the violence emerged both in response to apprehended infidelity and desertion.
Hafner and Boker (1982) examined a range of violent offenders, including homicide cases, and reported that 13% of all violent assaults were motivated by jealousy.
An analysis of the motives behind homicides provides further support for this idea. A cross-cultural study revealed that approximately one-third of all murders were driven by male jealousy within romantic relationships (Daly & Wilson, 1988). It is worth noting that this data is based on observational studies rather than experimental research.
Daly and Wilson (1988) argued these figures underestimate the role of jealousy, as many instances of jealousy are obscured by labelling the cause as "anger or hatred" or "argument.
Harris (2003) found that men reported higher levels of sexual jealousy in response to scenarios involving sexual infidelity, while women reported higher jealousy in response to scenarios involving emotional infidelity. This study suggests that men may be more sexually jealous when they perceive a threat to their partner's sexual fidelity. Harris found that males tend to exhibit greater arousal in response to sexual imagery, whether or not it is personally relevant to them. This aligns with existing research in psychology, which often investigates gender differences in physiological and psychological responses in various contexts, including sexual arousal and visual stimuli.
Another study by Mark KP and Janssen E. (2011) found that men reported more intense sexual jealousy in response to imagined sexual infidelity scenarios compared to women. However, it's important to note that this research area is complex, and results may vary depending on cultural, individual, and situational factors.
Setchell, J. M., & Wickings, E. J. (2005). "Dominant Male Mandrill Monkey Mate Guarding and Mating Success": This study on mandrill monkeys observed that dominant males engaged in mate guarding, a behaviour linked to ensuring reproductive success and paternity certainty. Such behaviours can be considered analogous to human behaviours, where males prefer fidelity-related traits.
Harris (2003) explored the evolutionary origins of jealousy and its sex differences. Findings: The research supported the hypothesis that men are more sexually jealous than women, as it is linked to concerns about paternity uncertainty.
DeSteno et al. (2002) investigated the emotional and cognitive mechanisms underlying sexual jealousy. Findings: The study found that men experience more intense emotional reactions to sexual infidelity, suggesting higher levels of sexual jealousy.
ANALYSIS
These studies contribute to our understanding of human behaviour, shedding light on patterns and tendencies. Still, it's essential to interpret their findings with caution, considering the broader context of the research.
ARE FEMALES UNFAITHFUL?
PARENTAL CERTAINTY - MOTHER'S BABY, FATHER'S MAYBE?
The concept of parental certainty, often phrased as "Mother's Baby, Father's? Maybe!" suggests that sex differences in parental care are influenced by the fact that females can be certain they are the biological parents of their offspring. At the same time, males cannot be as certain. This uncertainty arises from several factors:
Concealed Ovulation: Unlike many other species, human females do not display obvious signs of ovulation, making it challenging for males to pinpoint the most fertile period for mating.
Internal Fertilisation: Human reproduction involves internal fertilization, which makes it difficult for males to determine if their sperm successfully fertilized an egg.
Sexual Infidelity: The possibility of sexual infidelity means that males cannot be entirely sure that their partner's offspring are biologically theirs, especially if their partner has engaged in sexual activity with other males.
This paternity uncertainty can influence the level of investment and care males are willing to provide for offspring. Males may be more inclined to invest in offspring when reasonably confident about their biological connection. In contrast, females can be certain of their maternity due to gestation and childbirth. This concept is a key component of evolutionary psychology, helping to explain some of the observed differences in parental behaviour between males and females across various species, including humans.
TESTICLE SIZE IN PRIMATES
In primates, the variation in testicle size has been interpreted as supporting the parental investment theory regarding the fidelity of human females. The theory posits that the more sperm a male produces, the larger his testicles will be. But why would a male primate need a surplus of sperm? Evolutionary psychology suggests that larger testicles are advantageous for species with promiscuous females, as they engage in sexual activities with multiple partners.
For instance, chimpanzees, which have very promiscuous females, possess relatively large testes. In contrast, gorillas, which exhibit a more loyal mating system with fewer sexual partners per male, have smaller testes. Humans fall somewhere in between in terms of testicle size, implying that human females might have the potential for unfaithfulness.
This perspective on testicle size provides insights into primates' mating behaviours. It can be linked to the theory of parental investment, as it suggests that the testicle size in humans might indicate some aspect of promiscuity, which considers the reproductive strategies of various species (Mark Maslin, Professor of Palaeoclimatology, UCL, 2017).
MISATTRIBUTED PATERNITY
DNA studies have revealed that misattributed paternity, where the biological father differs from the assumed or official father, varies from approximately 1% in rural areas to as high as 30% in densely populated urban areas. It is estimated that around one in every ten live births results from female infidelity (Platek & Shackelford, 2006). This statistic implies that if a male chooses to invest his time and resources in raising children, there is a 1 in 10 chance that he may unknowingly be allocating his efforts toward children who are not biologically his own
OVULATION, FACE PREFERENCE AND CHEATING
Additional research on female infidelity suggests that not all females seek Alpha or highly masculine males as long-term partners. Studies indicate that face preferences in females are influenced by their menstrual cycle, particularly during ovulation. Women who are ovulating tend to prefer more masculine facial features, while those who are not prefer less masculine faces. Evolutionary psychologists have proposed that this preference shift is driven by a desire to mate with males possessing strong and healthy genes, even though these Alpha males may not make ideal long-term partners due to their high testosterone levels, which can lead to promiscuity and lack of empathy.
In contrast, females perceive non-masculine-faced men as better long-term partners and fathers. They believe these men are likelier to stick around, provide resources, and be faithful because they have greater empathy and lower testosterone levels (although potentially less favourable genes). As a result, females may engage in infidelity during ovulation with Alpha males and then misattribute the paternity of their offspring to their non-alpha male partner or husband. This complex interplay of mate preferences and ovulation adds further nuance to our understanding of human mating behaviour..
YOU LOOK LIKE DADDY
The importance of cues related to paternal certainty in human mating and parental investment is underscored by research such as that conducted by Daley and Wilson (1982). This study highlights how cues related to the child's resemblance to the father play a significant role in human behaviour:
Daley and Wilson (1982) conducted a study in a maternity ward where they recorded spontaneous conversations among family members. They observed that relatives, particularly fathers, were more likely to comment on the resemblance of the newborn baby to the father rather than the mother or other family members. This suggests that people are sensitive to the visual cues of resemblance, especially between fathers and their offspring.
Furthermore, the study found that mothers quickly reassured them when fathers expressed doubts about the child's resemblance. This indicates that the issue of resemblance and paternal certainty can be a significant concern in relationships.
In one recorded case from the study, a father even informed hospital staff that he would not support the child if the baby looked like his partner's former boyfriend, who was of a different race. This example highlights the potential impact of perceived resemblance on a father's willingness to invest in a child.
These findings suggest that humans, like many other species, pay attention to cues related to paternal certainty as part of their mating and parenting behaviours. Recognizing and responding to such cues may have evolutionary significance, as natural selection would favour genes that predispose males to ensure their investments are directed toward their biological offspring.
ANALYSIS
Drawing firm conclusions from the study conducted by Daley and Wilson (1982) can be challenging due to several limitations associated with the research:
Naturalistic Observation: The study relied on naturalistic observation, which captured conversations and interactions in a real-world setting. While this approach can provide valuable insights into everyday behaviour, it also has limitations, such as the lack of experimental control and numerous uncontrolled extraneous variables.
Lack of Experimental Control: Naturalistic observations do not allow researchers to manipulate variables or control the environment, making it difficult to establish causal relationships. In this case, the researchers recorded conversations without intervening, which limits their ability to draw definitive conclusions about the factors influencing participants' behaviour.
Sample Representativeness: The study's sample of participants may not have been representative of the broader population. Participants in a maternity ward may have unique characteristics or circumstances that differ from the general population, introducing potential biases into the observations.
Subjectivity and Interpretation: The study involved subjective elements, such as participants' perceptions of resemblance and their comments about it. Interpreting these subjective observations can be complex and may lead to different interpretations.
Given these limitations, viewing the findings from this naturalistic observation as exploratory rather than definitive is essential. While the study offers insights into how humans perceive and respond to cues related to paternal certainty, further research with more controlled methodologies and diverse samples would be necessary to validate and generalize these findings
MALES WILL NOT INVEST IN STEPCHILDREN
THE CINDERELLA COMPLEX
There is further support for the idea that the father's perception of paternity influences paternal care and investment in offspring by Burch and Gallup (2000):. Here's a breakdown of the findings:
Burch and Gallup (2000): This study found a positive correlation between how much fathers believed they resembled their child and the quality of their relationship with that child. Additionally, there was a negative correlation between the child's resemblance to the father and the severity of the mother's injuries in cases of spouse abuse. These findings suggest that fathers who are more certain of their paternity are more likely to invest in and have positive relationships with their children.
Anderson, Kaplan, Lam, & Lancaster (1999): Research indicates that stepfathers invest less in stepchildren than in their biological children. This supports the idea that individuals tend to prioritize investment in offspring with whom they share genetic relatedness.
The "Cinderella Effect": Martin Daly and Margo Wilson's analysis of homicide data revealed that stepchildren, particularly those living with a stepfather, are at a significantly higher risk of being harmed compared to children living with both biological parents. This effect aligns with evolutionary psychology, suggesting that stepparents may be less inclined to invest in stepchildren who do not share their genes, given the evolutionary perspective that parental investment is influenced by genetic relatedness.
The evidence presented in the previous discussion supports the idea that paternity certainty plays a role in shaping parental behaviour and investment decisions. According to parental investment theory and evolutionary psychology, individuals may allocate their resources and care differently based on their confidence in their genetic relationship with their offspring.
However, it's important to acknowledge that alternative explanations and criticisms exist. For example, Temrin et al. have challenged the evolutionary psychology explanation for the higher murder rate among stepchildren. They argue that genetic unrelatedness may not be the sole factor contributing to increased violence and criminal behaviour among stepfathers. Instead, they suggest that pre-existing tendencies toward criminality and violence in some males who become stepfathers could be a primary factor. In support of this, they conducted a study in Sweden, demonstrating that males who become stepfathers by marrying women who already have children from previous unions with other men are more likely to exhibit criminal and violent tendencies even before entering the stepfamily situation.
This perspective underscores the complexity of understanding differential parental behaviour in stepfamilies. While parental investment theory and evolutionary psychology provide a framework for interpretation, other factors, including individual traits and social context, may also be at play. Further research, such as the Swedish study conducted by Temrin et al., is needed to fully grasp the underlying causes of differential parental care in such family dynamics.
THE LOW MATE VALUE OF SINGLE MOTHERS?
This makes sense theoretically as divorced women with children are, on average, older, so they have lower mate value than younger women without children. According to Evolutionary psychology, all men would prefer to marry younger women without children rather than older women with children with other men. The logic of assortative mating would suggest that women with lower mate values are likelier to mate with men with lower mate values. And men with lower mate value are more likely to be criminal and violent.
Conversely, Anderson found that many men are likely to invest in stepchildren, disconfirming parental investment theory. A possible explanation for this behaviour is sexual strategies theory: men invest in stepchildren to show the women they have positive parenting skills, therefore increasing their chances of future mating.
Parental investment theory states that males do not invest in children that they do not believe to be their own; however, due to the mixed evidence on parental investment, it is questionable whether the amount of time and effort dedicated to our offspring is due to socialisation or merely has an evolutionary basis.
ADOPTED AND FOSTERED BABIES
While providing valuable insights into certain aspects of parenting behaviour, parental investment theory faces limitations in fully explaining the complexities of human parenting. It primarily focuses on evolutionary adaptations related to reproduction and offspring survival, emphasizing the allocation of resources and care based on genetic relatedness and reproductive success. However, there are instances where individuals adopt orphans and invest significant emotional and psychological resources into parenting.
These instances challenge the theory's predictions as they are often motivated by altruism, compassion, and emotional attachment, which do not align directly with the theory's emphasis on genetic relatedness. Human parenting is influenced by many complex psychological and social factors, including the desire for companionship, societal norms, and personal values, all of which can lead individuals to invest in children who are not their biological offspring.
Cultural variation also plays a significant role, with some cultures emphasizing the importance of adopting and caring for children in need, regardless of genetic relatedness. In modern societies, people have greater freedom to make choices about parenting and family structure, leading to diverse parenting practices that may not always align with strict evolutionary models.
In conclusion, while parental investment theory offers valuable insights, it cannot fully account for the richness and diversity of human parenting behaviours, especially those involving adoption and non-biological parenting. Understanding human parenting requires considering many emotional, psychological, cultural, and societal factors beyond the theory's scope.
DETERMINISM
Males and Promiscuity: It suggests that males may not be blamed or judged negatively for engaging in promiscuous behaviour. This perception aligns with the idea that males, from an evolutionary standpoint, may be inclined to pursue multiple sexual partners to maximise their reproductive success.
Females and Nurturing Roles: It implies that females may be expected or considered "normal" when they exhibit nurturing and motherly qualities. This expectation stems from the evolutionary role of females as caregivers and the importance of maternal investment in offspring.
SYNOPTIC ANALYSIS OF PARENTAL INVESTMENT THEORY.
The Parental Investment Theory (PIT) has faced criticism and debates in modern society. Here are some key points related to these criticisms and counterarguments:
EQUALITY OF WOMEN: Critics like Cozens (2005) assert that in modern individualistic societies, women have gained independence from men's financial support due to their ability to secure jobs and income autonomously. They emphasize that women have the means to obtain employment and access state-provided education, income support, and various social services. This access diminishes their reliance on male partners for child-rearing, aligning with the principles of parental investment theory.
CRITIQUE: Despite women's increased financial independence, the counterargument underscores single-parent families' challenges, where the male partner's contribution may be absent. Statistics indicate that children from such families may underperform in educational, professional, and romantic aspects. Furthermore, they exhibit higher susceptibility to mental health issues and involvement in criminal activities. For example, the association between single-parent households and crime, particularly in low-income communities, reveals some significant insights. Research indicates that family structure and the lack of paternal involvement are predictive of juvenile delinquency. Children with more opportunities to interact with their biological fathers are less likely to commit crimes or have contact with the juvenile justice system. In studies, a higher percentage of teenagers from father-absent homes were found to have higher incarceration rates compared to those from two-parent families.
The absence of a father in a child’s life may increase the odds of the child associating with delinquent peers and involvement in criminal activities. Boys from father-absent homes often lack male role models, which can affect their development and behaviour, including a higher likelihood of gang involvement. Furthermore, fatherless homes have been linked to various adverse outcomes, such as higher rates of childhood obesity, substance use, poor school performance, and mental health issues. ( Ethnicity Facts and Figures page). This suggests that the presence of a male partner, offering both financial and emotional support, can still offer advantages to children.
Lastly, proponents of this counterargument argue that relying on the state for support is fundamentally similar to depending on partners, as both sources provide crucial assistance during the early years of child-rearing. Furthermore, ample evidence exists supporting the notion of reduced cognitive abilities in children who experience childcare during their formative years.
CHILDLESSNESS AND HOMOSEXUALITY
Critics argue that the PIT/EP framework cannot explain couples' decisions to remain childless or the existence of homosexuality, where reproduction may not be a primary goal.
Counterargument: The argument put forth here centres on the role of sexual desire in human evolution. It highlights that evolutionary theory doesn't propose that humans have always engaged in sexual intercourse solely for procreation. Instead, the argument suggests that sexual desire itself has evolved as a natural trait because it increases the likelihood of humans engaging in sexual intercourse, which, in turn, enhances the chances of reproduction.
In this context, sexual desire is seen as a fundamental and instinctive aspect of human behaviour that serves to promote sexual activity. Without this innate urge, it would be less likely for men and women to engage in sexual intercourse, reducing the chances of reproduction. This perspective suggests that sexual desire is a product of evolution, ensuring that humans are driven to engage in sexual activity, even if they might not have fully understood the reproductive consequences of their actions in the distant past.
The argument also implies that this principle may not be unique to humans but could apply to other mammals, as sexual desire and mating behaviour are prevalent across the animal kingdom and serve as essential mechanisms for reproductive success. Evolutionary psychology doesn't necessarily dictate behaviour but seeks to understand the evolved psychological mechanisms underlying various human behaviours. It can still provide insights into the diversity of human behaviours, even in cases where reproduction is not the primary motive.
Regarding homosexuality, evolutionary theory doesn't view it as undermining parental investment but rather as a phenomenon that has its evolutionary explanations. One such explanation, often referred to as the "kin selection hypothesis" or "kin altruism," posits that homosexual individuals may not have offspring of their own but can contribute to the reproductive success of their close relatives. By helping to care for nieces, nephews, or siblings' offspring, homosexual individuals indirectly contribute to the transmission of shared genetic material within their family, which aligns with evolutionary goals.
This perspective suggests that sexual desire and orientation, including homosexuality, are complex aspects of human behaviour that can be understood within an evolutionary framework, and they do not necessarily undermine the principles of parental investment theory.
Lastly, electing not to have children and homosexuality can be viewed as extensions of individual freedom and choice. In modern societies, individuals have the autonomy to decide whether or not to have children or engage in same-sex relationships.
CHOICE AND BEHAVIOUR:
Critics of PIT have argued that it can be misused to justify or reinforce traditional gender roles and stereotypes. The argument is made that males and females should be free to choose and behave without evolutionary restrictions and pressures.
Counterargument: While PIT does examine differences in parental investment strategies between sexes, it does not inherently promote or endorse any sexist or misogynistic beliefs.
It is essential to understand that PIT is a descriptive theory that aims to explain certain reproductive behaviours observed in many species, including humans. It does not prescribe or dictate how individuals should behave. Instead, it helps scientists understand why certain patterns of parental investment have evolved in different species.
PARENTAL INVESTMENT CAN BE BOTH NATURE AND NURTURE:
Parental investment involves a combination of biological factors and environmental influences that shape caregiving behaviours:
Biological Factors: Evolutionary Predispositions: Evolutionary psychology proposes that certain parental behaviours are innate due to their adaptive value. Instincts like protecting and caring for offspring are considered evolved traits that ensure the survival of genes.
Hormonal Influences: Biological changes during pregnancy and childbirth, such as hormonal fluctuations, can influence maternal bonding and caregiving behaviours, fostering attachment and nurturing instincts.
Environmental and Societal Factors: Cultural Norms: Cultural expectations influence parental roles and behaviours. Different societies may have distinct norms regarding the division of childcare responsibilities, shaping individuals' approaches to parenting.
Social Learning: Individuals learn parenting practices from their upbringing, observing caregivers, and social interactions. Modelling behaviour from others contributes to the development of parenting styles and techniques.
Media and Education: Media representations and educational resources provide guidance and shape parental beliefs and behaviours. Parenting books, online resources, and educational programs influence approaches to child-rearing and decision-making.
Economic and Social Conditions: Socioeconomic factors, such as access to childcare services, employment opportunities, and community support, impact parents' capacity to invest time and resources in their children. Economic stability and social networks can affect parenting practices and family dynamics.
Overall, parental investment reflects a complex interplay between innate biological instincts and the cultural and societal contexts in which individuals live. The balance between nature and nurture varies across individuals and societies, leading to diverse parenting practices and attitudes. Understanding these dynamics is essential for comprehending the complexity of parental behaviour and its implications for child development.
PSYCHOLOGY AS A SCIENCE
Conducting experiments to test parental investment theory directly can be challenging. Parental investment theory is primarily based on evolutionary principles and observations of animal behaviour. Testing it in humans can be challenging due to ethical and practical constraints.
Post Hoc Nature of Parental Investment Theory: Parental investment theory is based on evolutionary principles and observations made after the fact. It proposes explanations for behaviours already occurring in human and animal populations. This retrospective nature makes designing experiments that can directly test the theory challenging, as researchers cannot manipulate the past. Instead, they rely on existing data, observations, and correlations to support the theory.
Isolating Variables and Establishing Causation: One of the central challenges in testing parental investment theory is isolating specific variables and establishing causal relationships. Many factors, such as cultural norms, individual differences, and social contexts, can influence parental behaviours. Disentangling these factors and attributing behaviours solely to evolutionary adaptations can be difficult.
Ethical and Practical Constraints: Conducting controlled experiments to manipulate variables related to parental investment in humans is often ethically and practically challenging. For example, it may be unethical to manipulate parenting behaviours that could harm children or go against societal norms. Researchers must rely on naturalistic observations, surveys, and correlational studies, which may not prove causation.
Complex Interplay of Nature and Nurture: Parental investment behaviours are likely influenced by a complex interplay of genetic predispositions (nature) and environmental factors, including cultural and societal influences (nurture). It can be challenging to disentangle these factors and determine the extent to which behaviours are shaped by biology or learned through socialisation.
Longitudinal Research: Longitudinal studies that follow individuals and families over time can provide valuable insights into the development and impact of parental investment behaviours. However, these studies often require significant time and resources and may face challenges in isolating causative factors.
In summary, like many evolutionary theories, parental investment theory faces inherent limitations due to its post hoc nature and the complexity of human behaviour. Researchers in this field must navigate ethical constraints, consider the multifaceted nature of the behaviour, and rely on various research methods to build a body of evidence that supports the theory's principles while acknowledging the challenges of establishing direct causation.
