SECTION: MATERNITY ASSURANCE
From Drmills
Contents |
INVESTING IN THEIR CHILDREN
FEMALE PROBLEM: Choosing the best times for pregnancy.
The ability of primates to socialize, as well as their increased learning capacity, has been made possible through increased pre- and post-natal care of primate mothers (Martyn, Price, & Foley, 1995).
In non-contraceptive-using societies (natural fertility), females display maximum fertility between twenty and thirty years of age. Between forty-five and fifty years old, the window wherein females experience the beginning of menopause, fertility decreases to zero.
POTENTIAL SOLUTIONS:
Avoid getting pregnant during hard times.
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<br>Topic: 1.2.1
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Contributor: Suzanne M. Banda<br>Class: Psyc 452, Fall 2008 Women of child-bearing age that are faced with a physical or mental stressor, either from an external cause or from themselves, have been shown to avoid pregnancy. This can be a mental or biological reaction to the unhealthy state of the female which is not optimal for child bearing.<br>One very important group to study on this topic is women with eating disorders, as countless women have (or are currently) dealing with these diseases. The rate of eating disorders in this population is estimated to be at about 5%. Miscarriages are at an increased rate among women with bulimia nervosa. Women with past eating disorders, particularly anorexia nervosa, tend to deliver babies of a much lower birth weight than other women. (Micali, M., Simonoff, E., & Treasure, J., 2007).<br>One of women’s worst fears is to be raped because it is an unwanted sexual encounter that may result in pregnancy. Many studies have found that women’s behaviors change in accordance with their state of ovulation. This variable set up against risky or nonrisky behaviors that can lead to rape have been studied by Broder and Hohmann (2003). To explain why surprisingly women are less likely to be raped when they are ovulating, it has been proposed by Chavanne and Gallup (1998) that “women may possess behavioral counteradaptations that protect them against rape during the ovulatory phase” (Chavanne & Gallup, 1998 as cited in Broder & Hohmann, 2003). This hypothesis was tested by Broder and Hohmann (2003) and found to be true as the group of naturally cycling women had a tendency to reduce risky behaviors and increase nonrisky behaviors when they were ovulating. As was anticipated, these tendencies were not found in women that were using hormonal contraceptives which suppress ovulation. This shows that women avoid the dangerous risk of pregnancy from an unwanted male through rape by acting in a more protective manner.<br>Petralia and Gallup (2002) also examined the effects of a woman’s menstrual cycle phase on their protective strategies to reduce their risk of rape. This study differs, however, in that it deals with the physiological reaction of handgrip strength and not of a behavioral strategy. The risks that follow rape for a woman are as follows: (1) lack of mate choice, (2) lack of protection from father, (3) possibility of being left by current mate, and (4) difficulty in attracting future mates (Sheilds & Sheilds, 1983; Thornhill & Thornhill, 1983, 1990 as cited in Petralia & Gallup, 2002). With such high risks at stake, it would make sense for a woman’s body to have evolved in a way to prevent being raped. This means that when they are ovulating, not only would women change their behaviors but they would also be physically better able to fight back when faced with an instance of sexual assault. Indeed this was found to be true in the study by Petralia and Gallup (2002). After reading a sexual assault passage, women that were ovulating had a significantly stronger handgrip measure than those that were not ovulating. This shows that the state of ovulation combined with the threat of assault (reading the passage) resulted in a physical change of an increase in strength. <br>A contrary finding to those previously mentioned is that females from stressful family environments (single-parent households, step-parent households) tend to have quicker reproductive development resulting in earlier first sexual intercourse and first pregnancy. The reason for this is that insecure attachment is a result of not having enough attention from parents (because mother is working two jobs, for example) and adults that have insecure attachment tend to move toward mating effort strategies. (Quinlan, 2003). From an evolutionary perspective, we would think that females with an unstable upbringing would not be as motivated to reproduce so early in life because they may not be equipped with the appropriate parental skills due to lack of exposure in their own home. Pregnancy at a young age can be detrimental to the mother and child as the mother’s relationship with the father is most likely an unstable one as well. <br>References: Broder, A., & Hohmann, N. (2003). Variations in risk taking behavior over the menstrual cycle an improved replication. Evolution and Human Behavior. 24, 391-398.<br><br>Micali, N., Simonoff, E., & Treasure, J. (2007). Risk of major adverse perinatal outcomes in women with eating disorders. British Journal of Psychiatry, 190, 255-259. Petralia, S., & Gallup, G. (2002). Effects of a sexual assault scenario on handgrip strength across the menstrual cycle. Evolution and Human Behavior, 23, 3-10. Quinlan, R. (2003). Father absence, parental care, and female reproductive development. Evolution and Human Behavior, 24, 376-390. <br>Relevant Website Links:<br>http://www.umm.edu/patiented/articles/what_risk_factors_female_infertility_000022_3.htm <br>http://www.aphroditewomenshealth.com/news/20060120230255_health_news.shtml <br>http://www.wcstx.com/prvntrpe.htm <br>
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Spacing pregnancies
Contraception, abortion, and infanticide
Contraception, abortion, and infanticide may seem particularly puzzling from an evolutionary perspective. Why would a female choose to reduce her reproductive success? As we will see, these are usually measures taken, on average, to increase the odds of her reproductive success over the long term.
For example, abortions are common in cases where the timing of a pregnancy may not be optimal. But, as a female's reproductive value declines with age, she is less likely to take interest in abortion as an option. A study at Ann Arbor, Michigan, for instance, showed that unmarried woman at or near their reproductive peak, as well as women related to them, are more likely to express pro-choice opinions compared to older women. In addition, laws restricting abortion are common in states with a low numbers of single, reproductively prime women (Betzig & Lombardo, 1991).
WHAT? In places where women do in fact have a choice of whether or not to have an abortion, decisions are affected by a variety of factors including the mother’s circumstances as well as the expectations of available investment by a father or alternative sources (Hill & Low, 1992).
Female Problem: Securing Male Investment in Offspring
Many predictions about parental investment come from the idea that women will be more attentive than men to cues of a prospective mate’s willingness to invest in children. Research conducted via the internet using 1,793 participants found that (a) women tend to generally be more critical than men in their evaluations of potential mates, but not potential friends or neighbors, and (b) cues of a positive disposition towards parental investment have a positive influence on female evaluations of the attractiveness of males.
Male parental investment has been an important factor in offspring survival, and females usually tend to seek male partners that are high in resources and status. Though status and resources are vital characteristics that women consider when choosing a mate, it is imperative to find a male that is fully committed to using those resources to raise and support a child. From an evolutionary viewpoint, assessments of another’s disposition towards parental investment (DPI) can expect to show marks of both the greater initial investments of females in offspring, and the possibility of substantial parental investment by males.
Willingness of a male to invest in a child can be judged by his disposition toward the idea of parental investments, and women should consider this behavior when choosing a mate. In general, women are predicted to pay more attention to cues of a male’s DPI and heavily utilize such cues in evaluations of males as suitable mates. According to Brase (2006), there are several general characteristics/possibilities that, when considering cognitive ability, would serve to assess parental dispositions. The first is an ability that works equally well for both men and women who are evaluating targets in any situation diagnostic of general traits (such as helpfulness and compassion). Second, it would be useful to have an ability that is differentially activated in women, rather than men. Third, there should be a capacity for an ability that is differentially activated in evaluations of opposite-sex targets. Specifically, this ability should be differentially activated in situations that are specifically diagnostic of parental investment. Brase (2006) argues that there should be an ability that embodies two of the three previous domain restrictions, and finally, that there should be an ability that embodies all the above domain restrictions. In other words, women are more sensitive than are men, specifically to contextual cues of parental investment dispositions of opposite-sex targets (potential mates).
La Cerra (1995) found support for these cognitive abilities, such as men displaying positive DPI producing higher attractiveness ratings from women as potential mates. This research shows that individual differences in DPI can be assessed as a potential mediator of one's perceived attractiveness. Women should be more critical than men in evaluations of attractiveness when dealing with all types of romantic relationships, and this sex difference should be related to the length and commitment of the relationship types (e.g, long- or short-term). Cues of positive DPI are predicted to have a positive influence on female evaluations of attractiveness of males; the higher the DPI, the more willing the female should be to copulate with the male, because she knows that her offspring will be well taken care of. Females are expected to choose mates that will be able to provide large investments presently or in the future (i.e., future resource acquisition).
However, this simple characteristic of choice can conflict with the female’s preference for indirect (good gene) benefits. These preferred males are known to provide fewer direct benefits (resources) than their rivals. In other species, there is no conflict between choice for direct and indirect benefits because the preferred males tend to provide the larger investments. By studying the courtship feeding between arthropods, Bussiere (2002) was able to find the relationship between direct (material) and indirect (gene) benefits to the female choice. In this study the author outlined a model that focuses on the idea of male investments being taxonomically more widespread than postnatal parental care. According to the study, males should allocate individual gifts if total gifts reserves are limited; the more limited the gift reserves, the smaller the optimal gift size. Gift size should also decrease as the abundance of copulation opportunities increase. Males chosen in pre-mating, or pre-fertilization post-copulatory mate choice, should donate smaller gifts than would be expected based on their condition. In insects, the mechanisms of post-copulatory mate choices depend on gift size, which can predict the donation ability of a male. This is especially true in arthropods, where material benefits are transferred during courtship so that females can store the sperm of more than one mate. In the system of post-fertilization parental care, female choice for indirect benefits cannot easily be dissociated from choice for genetic benefits. This is due to the fact that crucial direct benefits are acquired after the genetic benefits are fixed at fertilization.
Direct benefits are more important to choosy females than indirect benefits, according to a recent theory (Kirkpatrick, 1996; Kirkpatrick and Barton, 1997). Females thus use pre-mating choices to secure mates providing direct benefits, and use post-copulatory mate choice to favor the paternity of males providing indirect benefits irrespective of the material donations of those males. In other words, females benefit by acquiring a long-term mate with resources to help with parental investment, but may mate with several males and "choose" the one with the best genes to fertilize her eggs while maintaining relations with the long-term mate. Thus, she maximizes both direct and indirect benefits and increases the chances of survival and reproductive success of offspring.
There are two important forces involved in the evolution of female mating preferences: Direct selection acting on preference genes, and the “good genes” mechanism. It is also important for females to benefit immediately from their choice, such as by receiving resources. This immediate reward ensures that the female will repeat the behavior. Under strong sexual selection, resources and good genes are predicted to have a high correlation. In the absence of good genes, however, selection should establish preferences that maximize immediate survival and offspring fitness.
The correlation between a male trait and total fitness is postulated in the good gene hypothesis, such that females should select mates by using cues (traits) that reliably correlate with viability. The expression of a male display trait should be proportional to his genetic quality, which is (in part) determined by the number of mutations in a male's genes. In other words, natural selection will select for female preferences that reliably and accurately result in the selection of a mate with higher genetic quality. This selection process usually involves paying attention to particular cues or traits that can be used as indicators of this genetic quality. Mutations should (often) detract from genetic quality, and should be apparent in the organism's phenotype.
A good example in the animal kingdom is that of symmetry. Symmetry (such as in stripes or color patterns) is largely genetic and very salient (easily perceived). Natural selection should facilitate the evolution of mechanisms in a female that perceive symmetry, and result in her selecting the more symmetric individual as a mate. Furthermore, over time, these preferences will be increasingly correlated with the quality of the symmetry, because more symmetric individuals have (a) higher genetic quality, (b) increased appeal to potential mates, and thus (c) higher reproductive and survival success. Finally, males with a high mutation load should be less symmetric than males with a low mutation load, so that females can differentiate between potential mates with high or low genetic quality.
The correlation between preferences and male traits should evolve over time to be more reliable. The impact of good genes on mating preferences depends on how directly correlated the male trait is with overall genetic quality. Natural selection acting on genes underlying mate preference can place strong limits on this process. If the intensity of natural selection on preferences is strong, this is likely to cause the exaggeration of male traits by more than two or three phenotypic standard deviations (Alatalo et al., 1988).
The strength of selection on preferences depends on two qualities: (1) The genetic correlation between preferences and a potential mate's fitness, and (2) the rate of increase in fitness. The magnitude of preference-fitness genetic covariance (i.e., how much these variables vary together) is determined by female mating behavior and by the accuracy with which the male trait reflects his overall fitness. Thus, there will be high covariance if (a) females frequently prefer and mate with males who appear to have high genetic fitness based on phenotypic cues, (b) these traits do in fact correlate with genetic fitness such that (c) mating with these high fitness individuals substantially increases the survival and reproductive success of one's offspring.
Can Females Gain by Having Multiple Mates? The Game Theoretic Approach
Though females may rely on one male to become inseminated, in many animal species they engage in risky behavior by mating with multiple males. The most prominent benefit of polyandrous mating is acquiring multiple mates for parental investment. A limitation of this behavior is that if the male is also participating in promiscuous behavior, the female may have to share resources with his other female partners. Females can enhance their position by competing with rival females and monopolizing investments. Overall, polyandry is discouraged for females because the likelihood of diminishing paternal investment increases.
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| Topic: The value of mate value
Topic: The value of mate value
Class: Psych 452, Spring 2009
Rusu, S. A., & Bencic, A., (2003). Choosing a mate in Romania: A cognitive evolutionary psychological investigation of personal advertisements market. Journal of Cognitive and Behavioral Psychotherapies, 7(1), 27-43.
www.jsecjournal.com/NEEPSfishercoxbennettgavric.pdf
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| Topic: Female Quality Preferences in Choosing a Suitable Mate<br>Contributor: Jennifer Busico <br>Class: Psyc 310, Fall 2008<br><br>According to the research done by Schulte-Hostedde, Eys, and Johnson (2008), females prefer males who participate in team oriented sports, such as baseball or basketball, versus individual sport athletes, because it allows for females to visually assess the potential of the males. Sports provide an honest assessment of the male’s genetic fitness through their strength, speed, agility, ability to work well with others, and risk taking behaviors during the game (Schulte-Hostedde et al., 2008). “Females preferred males that participate in team sports over those who participate in individual sports or non-participants” (2008, p. 114). These males exhibit behavioral traits that are associated with good parenting and successful long-term relationships, such as, cooperation, role acceptance, and likeability skills. Furthermore, the male’s rank among his teammates holds a significant amount of importance. For instance, those males who are “benchwarmers,” though they participate in a team sport, are preferred less than those males who assume the role of “captain” (2008). In turn parents encourage their sons to engage in team related sports because it will ensure mating success, as long as they are active participants and not merely associated with the team (2008). This will allow for the genetic heritage to continue through future grandchildren.
<br>Strategizing, monopolizing, and aggressiveness are a few characteristics usually associated with the sport related male. Wilke, Hutchinson, Todd, and Kruger (2006) state that it can be assumed that a male involved in team related sports will be more inclined to engage in similar behaviors, seen during the sport, for his future mate and child. These researchers further discovered differences in attraction levels based on domain-specific risking taking behaviors. For instance physical risk-taking behavior, such as those behaviors seen during a sporting event, often illustrate how calmly or not so calmly a male performs under pressure (Wilke et al., 2006). This heightens a woman’s attraction to the male who performs well under pressure because he shows great potential for being considered as a long term mate. Sports oriented men lead females to believe that certain males are more capable of providing more resources than others (2006). A male advertises that in times of crisis, he will be able to still adequately provide and care for his family. <br>Todosijevic, Ljubinkovic, Arancic (2003) suggests that since the number of offspring a Homo Sapien female can conceive is limited an emphasis is placed on the reproductive strategy to attract a male who is able to sufficiently provide resources toward each offspring (Todosijevic et al., 2003). Women tend to be attracted to males that are of high economic status because these males not only gain access to proper resources, such as food, shelter, and clothing, but they also have the ability to control such resources. High status males usually contain certain personality characteristics such as, dominance and privilege. These qualities enable males to monopolize certain resources they deem important. The more a female considers herself as a higher status woman, the higher standards she holds for males (2003). <br>Nathan DeWall and Jon Manor (2008) found in during their research that high social status males capture more attention even when there is limited attention capacity (2008). Society is constantly faced with a plethora of stimuli on a daily basis, being able to apply complete attention towards one object seems impossible. However, DeWall and Manor found that women looking for long term mates have a higher sensitivity for noticing high status males. A high status male implies that a female can be provided for. Furthermore, even in times of cognitive overload, females are still captivated by a male who is of high status. <br>Females seeking long-term relationships look for many qualities that accurately assess a male’s reproductive success and parental investment. Those males who are involved in lacrosse, soccer, and rugby are at a higher advantage than their non-sporting counterparts to mate with a woman seeking a life long partner. However, the status of an individual on the team hierarchy plays an important role in a female’s choice. A sporting event is supposed to provide women with an easy assessment of a male’s potential; however, this does not imply that all males who play on a team sport will be chosen as mates. If a male is uncoordinated, slow, and scoring points for the wrong team a female will overlook them because his behavior does not provide the female with the assurance that she will be cared for. Women have an innate human response to positively react to males of high status, because it evokes financial security, a house, healthy offspring, and a comfortable life. Even if women are not ready to settle down, their senses are still heightened when confronted with a male of high status. <br> <br> <br><u>Related Links</u> http://www.forbes.com/2006/07/24/singles-dating-wealth-cx_lr_06singles_0725rich.html <br> <br> <u>References</u><br>Schulte-Hostedde, A., Eys, M., & Johnson, K. (2008, January 1). Female Mate Choice is Influenced by Male Sport Participation . Evolutionary Psychology, 6(1), 113-124. Retrieved from <http://www.epjournal.net/filestore/EP06113124.pdf>. Wilke, A., Hutchinson, J., Todd, P., & Kruger, D. (2006, July 13). Is Risk Taking Used as a Cue in Mate Choice. Evolutionary Psychology, 4, 367-393. Retrieved from <http://www.epjournal.net/filestore/ep04367393.pdf>. Todosijevic, B., Ljubinkovic, S., & Arancic, A. (2003, June 10). Selection Criteria: A Trait Desirability Assessment Study of Sex Differences in Siberia. Evolutionary Psychology, 1, 116-126. Retrieved from <http://human-nature.com/ep//downloads/ep01116126.pdf>. DeWall, N., & Maner, J. (2008, May 20). High Status Men (But Not Women) Capture the Eye of the Beholder. Evolutionary Psychology, 6(2), 328-342. Retrieved from <http://www.epjournal.net/filestore/ep06328341.pdf>. |
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FEMALE PROBLEM: Investing in their offspring
Female Reproductive Success and Inclusive Fitness
One of the strongest differences between the reproductive success of human males and females is the males’ ability to reproduce considerably more offspring than females. While men can theoretically reproduce over a span of about fifty years, multiple times a day, and thus potentially father thousands of offspring; women’s reproductive value is limited to a span of about twenty years and even further limited by the nine month gestation period of each offspring. Based upon the optimal number of offspring a male can reproduce versus a female during the lifespan, men clearly win the battle between the sexes over who is more reproductively successful, or so it seems.
Another unique difference between the reproductive strategies of men and women is the routes they take to increasing their reproductive success. While men usually strictly take the direct approach by just having their own offspring, women not only have their own children, but they also frequently take indirect routes of helping raise their kin’s kin as well as playing a more active role in the lives of their grandkids. The overall reproductive success, called inclusive fitness, of women consists of their own reproductive success plus the reproductive success of their kin. According to the kin selection and inclusive fitness theories (Hamilton, 1964), by helping genetic kin survive and reproduce, your shared genes can spread, thereby increasing your inclusive fitness. Because women are limited to the amount of offspring they can produce, to compete with the reproductive success of men, women find different strategies for increasing the frequency of their genes in future generations. Women maintain the assurance of their genes’ survival by varying how much they invest in each of their offspring, assisting other kin based upon kin selection theory, and by developing the adaptation of menopause to allow for grandmothering.
Maternal Investment
Based upon Robert Trivers’ Parental Investment Theory (1972), in most species women typically invest more in their offspring than men. One argument for this can be the idea that it becomes too costly for women to go through nine months of pregnancy and then the grueling pains of childbirth without guaranteeing the survival of their offspring. Thus, whatever children a woman has, the probability is high that she is going to do everything she can to make sure that child survives and then produces more kin. However, not every child a woman has receives equal amounts of her maternal investment. Depending upon the child’s age, size, and current reproductive value, a woman varies her maternal investment based upon each child’s needs and ability to survive on its own.
Unlike men who could potentially experience ‘paternity uncertainty’, women are 100% positive of who their offspring are and are better able to discriminate the allocation of their resources to the child who needs and deserves it most. Women invest more in those offspring who share more similar genes as well as offspring with higher reproductive value. As Mann (1992) showed, mothers invest more in healthier infants who also have higher reproductive value. From an evolutionary perspective, it makes more sense to allocate more resources toward the offspring that is most likely to survive and pass on more genes. If you invest more in unhealthy offspring and they end up dying, then you would have wasted all of those resources for nothing.
Similarly, in a study which examined 137 Israeli mothers whose children underwent neurosurgery due to chronic health conditions, it was found that a child’s age influences the amount of emotional investment and direct investment by the mother (Tifferet, 2007). The study supported the fact that women favor offspring with greater reproductive value as shown by the mothers’ increased emotional investment for the older children and decreased direct care for infants. This is because a mother has already invested substantial resources into an older child, as compared to a younger one. In summary, a woman is better able to increase the quality and survival of her offspring with the her ability to conduct a cost-benefit analysis of her maternal investment with each individual child.
Kin Selection
In addition to females’ varying degrees of maternal investment in their own offspring, women increase their overall inclusive fitness by also helping their relatives raise their kin. More than male kin, the influence of female kin on a growing infant’s life proves vital to their survival. In a study which examined the effects of kin on child mortality, it was found that the presence of female relatives did in fact have a significant positive effect on the survival of children (Sear, 2002). This study analyzed data in a rural area of Gambia between 1950 and 1974 and discovered that while having a living mother, maternal grandmother, and older sisters increased chances of survival, having a living father, paternal grandparents, and older brothers had no effect on child survival. Since the presence of the male relatives had no effect on child survival, it is likely that the presence of female relatives increase survival because they take a more active role in the lives of their kin’s offspring and have a more direct interaction with the offspring to ensure survival. This supports the idea that women, more than men, attempt to increase their inclusive fitness by taking a more hands-on role in helping raise the offspring of their relatives.
Menopause and Grandmothering (also, see section below)
Human females are especially unique in that their fertility fades when they go through menopause. After menopause, a woman’s reproductive value decreases to zero because she can no longer produce any offspring. If the point of life is to reproduce to ensure the survival of your genes, then why do women continue to live well beyond menopause? The grandmother hypothesis proposes that menopause evolved as a way of ending direct reproduction so that females can instead invest in their surviving children as well as their children’s children (Hill & Hurtado, 1991). It is proposed that, at menopause, it becomes more beneficial for women to allocate their resources toward current offspring and kin instead of reproducing more offspring. This means that the costs of having more offspring outweighs the costs of ceasing investment altogether so that women became more productive as investing grandmothers rather than investing mothers.
In fact, the existence of grandmothers is quite beneficial to the health and survival of their kids and grandkids. A research study which examined church register entries in Germany from 1720-1874 explored the effects of grandmothers on infant survival(Voland & Beise, 2002) . After analyzing the church registries, it was discovered that maternal grandmothers reduced infant mortality when the children were between six and twelve months old. Also, the infants’ risk of dying was 1.8 times higher if the maternal grandmother was dead at the time of their birth compared to if she was alive. Since the women in the role of a grandmother were already reproductively successful because their own offspring survived long enough to reproduce, their new role then becomes the insurance of the survival of their children’s children until reproductive age.
Even though women are unable to reproduce as many direct offspring as men, their presence in the lives of their relatives and in assisting to raise their kin’s offspring or grandchildren helps them to be as reproductively successful as men, if not more. Women increase their inclusive fitness through varying strategies of maternal investment, kin selection, and grandmothering.
Topic: PROBLEMS FACED BY WOMEN IN THE CURRENT UNNATURAL ENVIRONMENT
POTENTIAL SOLUTIONS:
Variable environmental conditions demand flexible reproductive responses (Bentley, 1999). A well-adapted organism can halt reproduction in stressful situations and resume it under more optimal conditions (Vitzthum, 1997). If future conditions are likely to be better than present ones, an adaptive organism will postpone reproduction. Our species has undergone such a selection process (Wasser & Barash, 1983).Frisch (1984), McFarland (1997), and Pond (1997) note that an inadequate percentage of body fat is a signal to the hypothalamus to reduce hormonal output. Reproductive self-suppression is cued by the hypothalamus, which inhibits hormone release in order to reserve fat supply for survival needs, such as maintaining warmth or storing calories. Fat reserves maintain pregnancy and are a source of lactose.
Seasonal changes in nutrition, (Bailey, Jenike, Ellison, Bentley, Harrigan & Peacock, 1992) energy expenditure, energy balance, and aerobic activity (Ellison, 1990) are all tracked by the ovarian system. Frisch (1983) and Warren (1983) note that endurance sports can result in anovulatory and amornorrheiic conditions, respectively. Thus, in female athletes who are involved in the most demanding fields, the arrest of ovulation and/or of menstruation are, from an evolutionary point of view, possibly adaptive, even though they are treated medically as abnormalities.
As has been noted, the adaptive responsiveness to the environment plays a role in determining the time of reproduction (Warren & Barash, 1983). The social context can also affect physical reproductive success. Family-related stress can inhibit ovulation (Harrison, 1997a&b). Wasser (1990) further emphasizes that these psychologically stressed women are as ill-suited as are physically stressed women to having and rearing children. The stressors of both categories have the same reproductive suppressing effect.
Anorexia occurs for the most part in young women in industrialized societies. Anorexia, which hides sexually maturity and nubile attractiveness, may be an adaptive response in young women to avoid pregnancy (Surbey, 1987; Voland & Voland, 1989; Anderson & Crawford, 1992).
Frisch (1983), Tanner (1981) and Warren (1983) suggested that due to diet in the industrialized nations, the onset of menstrual periods and sexual characteristics can appear in girls as young as eight years old. Anorexia may inhibit these girls, too young psychologically, from rearing children in their teenage years.
- Mealey predicts that incidence of anorexia is most likely among young girls who have been victims of rape, incest or who are single mothers.
- How many offspring
- Humans are inefficient child-bearers. Wood (1994) points out that onlyexually active w 15-25% of somen who are trying to conceive do so within a month, 50% within six months, and up to 90% after 12 months. Not all of these come to term and Anderson (1990) notes that most of those that do result in a single offspring. Wood also notes that lactation then delays conception.
- Nesse and Williams (1991, 1994) see these inefficiencies as evolutionary mechanisms that are sensitive to optimum conditions for reproduction. Kozlowski and Stearns (1989) say that these mechanisms allow mothers to select timing and qualities in offspring.
- Forbes (1997) and Neel (1990) discovered that chromosomal deviations did not come to term as frequently as they spontaneously aborted. This implies that although the fetus can survive in utero, some mechanism is filtering it out before it is born, perhaps causing maternal death. Miscarriage stops the investment of maternal resources in a potentially deformed baby. She can then attempt to conceive again sooner.
- A signal (the chorionic gonadotropin secreted by the placenta) tells the mother that the embryo is normal and healthy (Haig, 1993). An unhealthy embryo cannot emit the signal. Thus, a miscarriage can increase efficiency (Forbes, 1997).
- When a woman is older, her screening becomes more lax. She enters a last chance phase for reproduction. Thus she may carry to term an embryo that is not emitting sufficient signals (Kloss & Nesse, 1992; Forbes, 1997).
- Forbes, 1997, has found that although the older woman’s eggs are fine, she will still bring to term more abnormal fetuses that her younger women counterparts. IF older eggs are not the problem, it stands to reason that there is evidence for the hypothesis that accounts for the less stringent screening process of the embryo that cannot signal its health.
- Lactation spaces births, but not inefficiently. Anderies (1996), Blurton Jones (1986), Vitzthum (1997) are some of those who have concluded that the spacing allows maximum nutrition for the child and is best for the mother and the next child. Therefore, lactation amenorrhea is adaptive.
- Infant mortality has dropped significantly in cultures of good nutrition and hygiene. In these cultures, menarche comes earlier, menopause later, and lactation periods are shorter, resulting in a population explosion. After two generations of low death rates, birth rates typically drop as well. As though deliberately and consciously curbing population growth, women are delaying conception by choice (contraceptives and planning). Even modern contraception could be viewed as a continuation of evolutionary history (Baker & Bellis, 1995).
Sex-ratio manipulation
At conception there are significantly more males than females. Because males suffer more fatalities at various stages of development, by adulthood, the numbers are about equal. Men continue to suffer more fatalities than do women throughout the life cycle. While in utero, prenatal manipulation occurs through conception timing, the chemistry of the vagina and the physiology of the uterus.
Grant (1998) has found evidence that women can and sometimes do unconsciously manipulate the sex of their children. This is known as the Trivers—Willard model of sex ratio determination.
Chahnazarian (1988), Mealey (1990) and several other studies of sex ratios at birth show that, in both human and nonhuman animals, parents high in social dominance and with access to greater resources, tend to have more sons. Using postnatal neglect and infanticide as measures, in high-income families there was an apparent bias in favor of sons (Choe, 1987), whereas in low-income families there appears to be a bias for daughters (Cronk, 1989)
| Topic: Sex ratio manipulation: Are males preferred over females?
Contributor: Antú Schamberger
Various animal species have been found to manipulate sex ratios in an array of situations. Sex ratio theory suggest that when the environment influences the fitness of one sex over the other the parents will adjust their offspring ratios to correspond to maximizing their overall fitness. Nager, Monaghan, Griffiths, Houston, & Dawson (1998) hypothesized that species which determined their sexes chromosomally, such as birds and mammals, would manipulate the sex ratio at birth or in laying eggs. Research results demonstrated that males hatched less often than females when the female producing the eggs came from poor living conditions. The mothers tended to skew the sex ratio towards the sex that had the higher survival expectancy under certain conditions (see Figure 3). This is simply attributed to the idea that males need more resources to survive when under parental investment than do females.
When it comes down to food availability animals tend to be biased towards the sex that will be more likely to survive. Kilner (1998) found that when food was restricted zebra finches would favor the male sex thus implying that female chicks would have a higher mortality rate when food was low after the parental investment period compared to male chicks. As stated earlier the theory of sex ratio manipulation holds down in various animal species. The most common male to female ratio studied among natural populations is 1:1. This ratio changes when the benefit of one sex is more than that of the other sex. The struggle occurs between the selective factors to balance out the sexes versus the reproductive value expected from either sex. For example, Crognier (2005) states that if one sex becomes less costly and is more rewarding as to genetic return then its frequency will grow. Also, if one sex tends to die more often before the end of parental investment then their frequency will drop. Fisher’s theory suggests that when males and females cost different amounts of parental investment the ratio will shift but interestingly enough the investment in both sexes remains the same (Crognier, 2005). Another hypothesis specified by Crognier was that of Trivers and Willard where natural selection chooses a reproductive strategy that corresponds to reproductive success in one sex, which is influenced by the parental investment in that specific sex. Parents therefore should invest more in the sex that is favorable in certain situations and reverse that investment when circumstances change. To illustrate further, males will be favored when the parental investment has lead them to be healthy because then they will reproduce more than their fellow female siblings. In contrast, if the male is not healthy because parental investment was detriment to their health then they will not attract other females and their female siblings will gain more offspring. When this hypothesis is juxtaposed with human beings theory states that wealthy families are going to rear male offspring and poor families will rear female offspring. This is simply because, as stated earlier, parents that can invest more in their offspring (more resources to allocate) will be biased towards having male children.<br> Some researchers have adopted the idea that the sex manipulation of the offspring is due to social status, which was briefly stated above. Mealey & Mackey (1990) research focused in on the wives of first and second ranked well off Mormon families and found that these families who are high on the social latter tend to have more offspring who are males compared to females. This is simply because males with more resources are more appealing to other mates. Consequently, families of low social status have a bias towards having more females than males. The question follows as to what determines this sex selection. On a genetic level the sex of an offspring is comprised of the X or Y the male contributes to the ovum. It is seen as a random by chance process that the sex of an offspring is selected. Coney & Mackey (1998) disagree with the previous statement and contribute to the idea that there are selective factors that add to the conception of a male over a female, which is termed the primary sex ratio. The researchers pose also a secondary sex ratio, which has selective factors that contribute to sex biased miscarriages. The main thought is that sex selection is facultative and there are biases for either a male or the female progeny. Overall, there are many theories that point to reasons as to why sex ratio manipulation exists and even if there are selective factors that contributes to the bias of one sex over the other. But when it comes down to actual research done in the field it is hard to see what happens in animal species at a human level. This can simply be attributed to the fact that humans have a more complex social structure than that seen in animal species. This does not mean that sex manipulation is not actually happening in human societies because there is experimental evidence for an adaptive and facultative manipulation of sex ratios. It is just the case that these theories might need a bit more of reinforcement. <br> Reference list: Coney, N. S., & Mackey, W. C. (1998). The Woman as Final Arbiter: A Case for the Facultative Character of the Human Sex Ratio. The Journal of Sex Research, 35, 50-64. <br> Crognier, E. (2005). Culture universals and genes. Human Evolution, 20(1), 1-18. <br> Kilner, R. (1998). Primary and secondary sex ratio manipulation by zebra finches. Animal Behavior, 56(1), 155-164. <br> Mealey, L. & Mackey, W. (1990). Variation in offspring sex ratio in women of differing social status. Ethology and Sociobiology, 11(2), 83-95. <br> Nager, R. G., Monaghan, P., Griffiths, R., Houston, D. C., & Dawson, R. (1998). Experimental demonstration that offspring sex ratio varies with maternal condition. Ecology, 96, 570-573. <br> <br> Additional web resources: Presidents preferred sons<br>link: http://www.jstor.org/pss/4236098 Why Parental Sex Ratio Manipulation is Rare in Higher Vertebrates<br>link: http://www3.interscience.wiley.com/journal/118949452/abstract?CRETRY=1&SRETRY=0 Diet, maternal condition, and offspring sex ratio in the zebra finch, Poephila guttata<br>link: http://journals.royalsociety.org/content/qu3drbn79h7hw6ll/ Parental care and adaptive sex ratio manipulation in birds<br>link: http://journals.royalsociety.org/content/0b8dg4u8l3eul2uf/ Sex ratio and mate preference: A cross-cultural investigation<br>link: http://www3.interscience.wiley.com/journal/112748438/abstract Preference for sons and sex ratio in two non-western societies<br>link: http://www3.interscience.wiley.com/journal/112596557/abstract#relatedArticles <br> <br> |
Maternal-fetal gestational conflict
Weening and the resumption of fertility
Deciding how many offspring to have
Motherhood vs. career
Career vs. Motherhood: Is it necessary to make that choice?
We are in the midst of a “subtle revolution.” Even seasoned observers, armed with statistics, are pointing to changes in women’s behavior so vast as to warrant this label. Current concerns about the “new working woman” and the “new choice of motherhood” reflect a growing awareness among experts and observers alike of the far-reaching changes taking place in the work and family patterns of American women.
The growth of women’s employment has been one of the most sustained and widespread changes within American and European societies over recent decades. Between 1960 and 1990 the European labor force grew by 30 million, with 25 million of those being women (Rubery et al. 1999). Thus we have seen a profound restructuring of social organization where these associated countries have moved in the direction from the breadwinner-housewife system to a system characterized by dual-earner households.
The growing necessity of reconciling work and child care was the focus of much social science and policy research and debate during the 1990s. Yet, many people within the United States and other countries feel a different way about the ‘working mother’. Nineteenth century Swedish writer Ellen Key states, “The Mother is the most precious possession of the nation, so precious that society advances its highest well-being when it protects the functions of the mother.” Agreeably so. Maternal selflessness has endowed mothers with a unique moral authority which has been used to promote temperance, maternal and child health, the importance of pre-school education, a more lenient juvenile system, and recently, to combat drunk driving. It has been said time and time again that child rearing is the most important job in the world. For this reason, many believe it cannot be juggled with other priorities and responsibilities such as that of an additional career. Motherhood, many agree, must be your career.
The growing controversy in many nations has prompted the question: Is it necessary to make the choice between motherhood and career? The argument in favor of women making that choice between motherhood and career certainly has some valid points. A 2005 New York Times article by Louise Story assembles and frames anecdotes about undergraduate females at a top university to suggest—without directly saying so—that women's values about career vs. motherhood are in flux. The article discusses that the majority of women at elite colleges around the United States have already set their career path toward motherhood. Its findings state that many women at the nation's most elite universities say they have already decided that they will put aside their careers in favor of raising children when the time comes. Though some of these students are not planning to have children and some hope to have a family and work full time, many others say they will happily play a traditional female role, with motherhood as their main commitment.
It is frustrating for many to thrive within a society in which this choice between motherhood and career is focused primary on the female. A man’s working life and occupational career is by and large not affected by his family situation. However, when women get married (or start a cohabiting relationship) and, even more, when they have children, they allocate more time and more of their energy to unpaid housework and less to paid work outside the home, which in turn means that their career possibilities are reduced compared to that of a man. On the other hand, there are many who believe that a mother can absolutely have it all. As society changes and the roles of women become more complicated, many women are deciding to combine motherhood with a career. This seems to be an ideal situation. A woman can fulfill her own dreams of success in the world and still have the family that she wants.
The good news is that times are changing, and society is beginning to reflect that change. The rest of the world is recognizing what women have always known. Bright females who want both a career and a family can look forward to succeeding at both. Research from Dex and Joshi (1999) points out that the women’s reproductive role has been thought to conflict with lifetime employment for women, with negative implications for either market productivity or fertility. However, confronted with the choice between three labor market possibilities (to participate part-time, full-time, or not at all), a new mother is much less likely today to quit her job for an extended period of time. This is one reason that the perception behind women facing a stark choice between career and family is becoming less accurate in each successive decade.
On another note, research by Hock, Gnezda, and McBride (1984) discusses attitudes toward employment and motherhood following a woman’s first child. It states that the reasons often cited for the increased labor-force participation of mothers of young children are a) the increase in single-parent female-headed households resulting from the accelerated divorce rate and increased incidence of births to single women and b) the need for two incomes in intact two parent families to ensure economic stability and/or survival in precarious economic times (Hock et al., 1984). This evidence points to the idea that often times a woman may not have the luxury of staying at home to solely raise their child for economic reasons. In addition, many individuals are not willing to put their dreams of motherhood on hold indefinitely simply because of their financial circumstance.
Perhaps, most importantly, surely there is reason to believe that women who combine motherhood and career give their spouse or partner more opportunity to participate in roles that have become stereotyped as a woman’s responsibility; for example, there may be a more egalitarian split between parents in such tasks as child care, meal preparation, house cleaning, etc. This creates less of a pressurized situation for both people involved, as the husband can pick up more household responsibilities in return for having a dual-income household. Additionally, a woman may feel a sense of accomplishment by achieving this balance of independence, intelligence, and bread winner in her life. Some females feel that by attaining these key things, it allows them to be better mothers -- more nurturing and understanding than if they were primarily stay-at-home moms. For this reason, why not? Go ahead, dream big - plan to have it all. However, be sure to back up those dreams with a foundation of priorities, role models to turn to for advice and, perhaps most importantly, a partner that will support your endeavors as a mother who wants to have the best of both worlds.
Women in the workplace
Contributor: Brittany Sutter
There have been very dramatic changes in the workplace over the past fifty years. This paper will examine specifically the changes for women, and more pointedly the continuing inequity in income for women. Women have been increasingly moving out of the home and into the workplace. In 1900 only 20% of women were working outside the home. The numbers rose to 59% in 2005 (Barreto, Ryan, and Schmitt, 2008). As cited by Baretto et al. (2008), Catalyst, 2007, it was reported that in the United States, women make up less than 16% of corporate officers, and less than 15% were members of the board of directors in Fortune 500 companies. Women today want to have it all; a successful career, and motherhood. The truth is most women are “stopped dead, long beforehand, by the maternal wall” (Porter, 2006, p.56). This wall affects women with children in so many ways, including hiring, promotions, pay, and terminations. Since only women have children, they are not considered ideal workers due to pregnancy, maternity leave, and child-rearing demands they are sometimes absent from work. Courts even view women differently, for example as in sexual harassment laws, and this means women with children are treated more poorly than their male and female childless counterparts. This limit on women in the workplace has been described as the glass ceiling. The term describes the phenomenon in which men dominate the upper income jobs. The word ceiling implies that women have an upper limit on how much they are paid and how high up the business ladder they are allowed to climb. The word glass refers to the subtle and transparent barrier (Barreto, Ryan, and Schmitt, 2008).
A study by the U.S. Department of Labor and U.S. Bureau of Labor Statistics (2009) reports that in 2008 women made an average weekly earning of $638, which is 80 percent of the men’s average earnings of $798, whereas in 1979 women only earned 62 percent as much as men. This shows improvement for women, but not equality. Gender pay differences are still a problem for women. In a study by Joshi, Makepeace, and Dolton (2007), the gender wage gap for full-time workers in their thirties showed improvement for women due to improvements in women’s education and experience. This study did not indicate improvement in equal treatment. In fact, their study concluded that if a woman full-time worker in 2000 had been paid at men’s rates she would have actually received higher pay than the typical man (Joshi et al., 2007).
Eighty-five percent of women become mothers during their working lives (Porter, 2006). When a women has a baby and returns to work she is often assigned to less challenging jobs because it is assumed that her heart and head are with her baby and not at work. Working mothers will miss opportunities that would involve work related travel. Many things which results in lower bonuses or promotions she wont get. It is interesting to note the difference that the new fathers experience compared to new mothers. New fathers are given extra work and are expected to stay late because they now have a family to support. In contrast new mothers are sent home at 5:30 P.M. to go home and care for the child. She is now perceived more as a low-competence caregiver than the working woman she was a few short months ago (Porter, 2006).
When parents are wealthy they can afford a nanny, which would allow them to work unlimited hours. However, most parents are not, and therefore need to figure out who will be the primary care giver for the children. This means that one parent must put their career on hold. Since women usually are paid less than men it becomes the wife who puts her career behind the husband’s career. If she continues to work, overtime is out of the question because she needs to pick up the children. The mother must miss work for children’s illnesses, school events, and doctor’s appointments. A woman is less likely to relocate because her husband would not want to leave his job. Many women are given reduced-hours in order to keep working, but women who opt for reduced hours are viewed as less visible, less important, and less worthy.
There are other very subtle differences when a woman becomes a mother in the workplace. There is now a negative stereotype that alludes that she is no longer considered a competent career woman, now she is perceived as a housewife. She is considered “high in warmth but low in competence, close to … the blind, disabled, retarded, and elderly” (Porter, 2006, p.58). The idea that women belong in the home is still very prevalent.
Another problem for women is a woman’s biological clock. Women who want to focus on their career may start to hear their “biological clocks” ticking away with time. Right around when women are about to establish their careers is exactly when the ticking of the clock gets louder, hence making women decide between career or motherhood. Thus, many women have started to embrace a “male-model” of single-mindedness on career focus. Among professional women this has led to an “epidemic of childlessness” (Gibbs, 2002, p.1). Gibbs explains a study where Hewlett conducted a national survey of high achieving women. The results showed that 42% of these women in corporate America were still childless after age 40, and the figure rose to 49% for women who earned $100,000 or more. These women made a lot of money but at a cost. Women pay the cost of parenthood with their careers.
Barreto, M., Ryan, M.K., & Schmitt, M. T. (2008). Introduction: Is the glass ceiling still relevant in the 21st century?. The glass ceiling in the 21st century: Understanding barriers to gender equality. Washington, DC US: American Psychological Association.
Gibbs, N., (2002, April 15). Making time for a baby. Time, subscriber access, www.time.com/time.
Joshi, H., Makepeace, & G., Dolton. (2007).More or less unequal? Evidence on the pay of men and women from the British birth cohort studies. Gender, Work and Organization, 14(1), 37-55.
Porter, N.B. (2006). Re-defining superwoman: an essay on overcoming the "maternal wall" in the legal workplace. Duke Journal of Gender Law & Policy, 13(55), 55-84.
U.S. Department of Labor & U.S. Bureau of Labor Statistics. (2009, July). Highlights of women’s earnings in 2008. Retrieved from: www.bls.gov/cps/cpswom2008.pd
The Trade-Off: Empirical Studies
What makes a fit mother? Does being a fit mother mean spending all of one's time with a child? Or is there a balance such that women are also able to achieve their career goals? Some studies show that a mother’s decision to have children and a job may affect the children that they raise. Other studies, however, indicate that the time a mother spends with the child has no effect on the child. It is up to the mother to decide which path she thinks will best suit her child and herself.
Huston and Aronson (2005) conducted a study that examined the amount of time mothers spend with their children. According to these authors, the results “provide support for the prediction that mothers who spend more time with their infants, particularly time devoted to social interaction, are more sensitive and provide higher quality home environments during the child’s early years” (p. 478). Although they found that more time spent with children seems to create a better environment, the question of whether a working mother can have the same amount of quality time with their children remains.
A study by Goldberg, Prause, Lucas-Thompson, and Himsel (2008) seems to answer to this question. These authors examined how a mother’s time at work affects their children. They argued that the time a mother spends with the child correlates to the child's achievement, but the results showed that “the significant effects usually were in the direction of a favorable effect of maternal employment on children’s achievement” (p.105). Similarly, McGroder, Zaslow, Papillo, Ahluwalia, and Brooks (2005) sought to determine whether a working mother’s time spent at work had effects on children. “Contrary to hypotheses regarding anticipated effects of maternal employment under mandatory circumstances, employment secured through Atlanta’s mandatory LFA programme appeared neither beneficial nor detrimental to children” (p. 346). These studies indicate that a mother can be a successful parent, regardless of whether she has a career.
Grandmothering
Menopause
Menopause is the natural cessation of a woman’s menstrual and reproductive cycles, and most women experience menopause around the age of 50. As women become older, their reproductive success level drops. One main reason why this occurs is the “exhaustion of ovarian oocytes” (Kirkwood & Shanley, 2001, p. 282) because women have a fixed number of them. Researchers have several different hypotheses to explain why menopause occurs and what its purpose is, such as the “grandmother hypothesis” that emphasizes the importance of a maternal grandmother in the life of a child. An alternative hypothesis is the “absent father hypothesis,” which implies that, because ancestral males died at a younger age than women, middle-aged women might have felt necessary to continue reproduction by investing in the offspring of kin.
Kuhle (2007) proposed the grandmother hypothesis, which explains that menopause evolved because ancestral middle-aged women had greater reproductive success when they invested in existing genetic relatives rather than continuing reproduction. Middle-aged women have a higher risk of death during pregnancy than younger women. Furthermore, children of middle-aged women receive less maternal time than children of younger women.
Kuhle also proposed the “adaptive onset hypothesis.” He argues that “selection could have linked the timing of menopause with the likelihood that any children a middle-aged woman could produce would survive to reproductive age” (Kuhle, 2007, p. 335). Kuhle concluded that natural selection could have favored of the evolution of menopause as an adaptation for a continual reproductive strategy.
In Kirkwood & Shanley (2001), the authors argued that menopause may be a result of the extreme dependence of human babies on their parents, along with the difficulties associated with giving birth (Kirkwood & Shanley, 2001). The researchers emphasized the fact that it is more adaptive for a woman to slow down reproductively rather than run the risk of harm, such as a situation where the mother dies early in a child’s life. For example, a child younger than 2-years-old will not survive if the mother dies whereas a child who is 15-years-old has better chances of survival. Kirkwood & Shanley also discussed the grandmother hypothesis, arguing that menopause enhances fitness by producing “post-reproductive grandmothers who can assist their adult offspring by sharing in the burden of provisioning and protecting their grandchildren” (Kirkwood & Shanley, 2001, p. 282). Thus, help from the maternal grandmother can increase a woman’s reproductive success and decrease the chances of mortality during childbirth.
However, the results from these models provide little for the evolution of menopause on its own, but if combined with other models, there is a supportive model for the role of menopause. This composite model “suggests that evolution of menopause is a process that has its roots in complex features of the human life history” (Kirkwood & Shanley, 2001, p. 285). Life history theory has been employed by researchers to explain how organisms allocate resources toward different goals. Because there are a limited amount of resources, the way in which an organism allocates its resources (toward either mating or somatic effort, for example) is likely to reflect the environmental context. The strategy that works best, in other words, depends on the situation.
Shanley, Sear, Mace, & Kirkwood (2007) tested two main evolutionary explanations for menopause: the likelihood of maternal mortality with age and the grandmother hypothesis. The researchers tested these hypotheses based on data gathered from populations from four villages in Gambia during the period of 1950-1975. Shanley et al. (2007) wanted to assess whether menopause enhanced fitness in comparison to women whose fertility was continued past the age of 50. Their results yielded the fact that child survival depended on maternal survival, but only during the first two years of life. The maternal grandmother also had a significant influence on child survival after the first two or three years, thus supporting the grandmother hypothesis. Although the researchers did not find strong statistical support for the reason why menopause occurs around the age of 50, they hypothesized that a woman living beyond 50 and remaining fertile would require the maintenance and repair of a woman’s body and her ovaries, a process that may be too costly.
Hall (2003) used an energetics-based approach to explain menopause. She addressed the fact that a combined model that explains menstruation and menopause is needed to understand both cycles. Energetics “refers to nutrient transformations of a physical, chemical, or biological system, and thus provides the metabolic cost of key adaptations” (Hall, 2003, p. 84). Hall identified that negative biological influences, such as tobacco smoking, can cause early menopause and increase the pace of egg cell loss. Older females would be expected to have fewer menstrual cycles due to the deterioration of oocytes and the increasing chance of early fetal loss. Menopause also decreases the chances of a woman to die during childbirth, especially if they are over the age of 50. In addition, due to the fact that menstruation consumes energy, menopause would help older women save their energy for other activities, such as investing in other kin.
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