Bateman's Principle in Evolutionary Biology
In most species, variability in reproductive success (or reproductive variance) is greater in males than in females.
factor of parental investment, over which
males will compete in order to
copulate successfully.
Although Bateman's principle served as a cornerstone for the study of sexual selection for many decades, it has recently been subject to criticism. Attempts to reproduce Bateman's experiments in 2012 and 2013 were unable to support his conclusions. Some scientists have criticized Bateman's experimental and statistical methods, or pointed out conflicting evidence, while others have defended the veracity of the principle and cited evidence in support of it.
Description
Typically it is the females who have a relatively larger investment in producing each offspring. Bateman attributed the origin of the unequal investment to the differences in the production of gametes: sperm are cheaper than eggs. A single male can easily fertilize all of a female's eggs; she will not produce more offspring by mating with more than one male. A male is capable of fathering more offspring if he mates with several females. By and large, a male's potential reproductive success is limited by the number of females he mates with, whereas a female's potential reproductive success is limited by how many eggs she can produce. According to Bateman's principle, this results in sexual selection, in which males compete with each other, and females become choosy in which males to mate with. Thus, as a result of being anisogamous, males are fundamentally promiscuous, and females are fundamentally selective.
https://en.wikipedia.org/wiki/Bateman%27s_principle
Trivers' Parental Investment Theory
Parental investment as defined by
Robert Trivers in 1972 is the
investment in offspring by the parent that increases the offspring's
chances of surviving and hence reproductive success at the expense of the
parent's ability to invest in other offspring. A large parental investment
largely decreases the parents' chances of investing in other offspring.
Parental investment can be split into two
main categories: mating
investment
and rearing investment.
Mating investment consist of the sexual act and the sex cells invested.
The rearing investment is the time and energy expended to raise the offspring after conception. In most species, the female's parental investment in both mating and rearing efforts greatly surpasses that of the male. In terms of sex cells (egg and sperms cells), the female's investment is typically a larger portion of both genetic material and overall verillity, while typically males produce thousands of sperm cells on a daily basis.
Human parental investment
Human women have a fixed supply of around 400 ova, while sperm cells in men are supplied at a rate of twelve million per hour. Also, fertilization and gestation occur in women, investments which outweigh the man's investment of a single effective sperm cell. Furthermore, for women, one act of sexual intercourse could result in a nine-month commitment such as human gestation and subsequent commitments related to rearing such as breastfeeding. From Trivers' theory of parental investment, several implications follow. The first implication is that women are often but not always the more investing sex. The fact that they are often the more investing sex leads to the second implication that evolution favors females who are more selective of their mates to ensure that intercourse would not result in unnecessary or wasteful costs. The third implication is that because women invest more and are essential for the reproductive success of their offspring, they are a valuable resource for men; as a result, males often compete for sexual access to females.
Males as the more investing sex
For many species the only type of male investment received is that of sex cells. In those terms, the female investment greatly exceeds that of male investment as previously mentioned. However, there are other ways in which males invest in their offspring. For example, the male can find food as in the example of balloon flies. He may find a safe environment for the female to feed or lay her eggs as exemplified in many birds.
He may also protect the young and provide them with opportunities to learn as young, as is the case with many wolves. Overall, the main role that males overtake is that of protection of the female and their young. That often can decrease the discrepancy of investment caused by the initial investment of sex cells. There are some species such as the Mormon cricket, pipefish seahorse and Panamanian poison arrow frog males invest more. Among the species where the male invests more, the male is also the pickier sex, placing higher demands on their selected female. For example, the female that they often choose usually contain 60% more eggs than rejected females.
This links Parental Investment Theory (PIT) with sexual selection: where parental investment is bigger for a male than a female, it's usually the female who competes for a mate, as shown by Phalaropidae and polyandrous bird species. In these species females are usually more aggressive, brightly colored, and larger than males, suggesting the more investing sex has more choice while selecting a mate compared to the sex engaged in intra-sexual selection.
Females as a valuable resource for males
The second prediction that follows from Trivers' theory is that the fact that females invest more heavily in offspring makes them a valuable resource for males as it ensures the survival of their offspring which is the driving force of natural selection. Therefore, the sex that invests less in offspring will compete among themselves to breed with the more heavily investing sex. In other words, males will compete for females. It has been argued that jealousy has developed to avert the risk of potential loss of parental investment in offspring.
If a male redirects his resources to another female it is a costly loss of time, energy and resources for her offspring. However, the risks for males are higher because although women invest more in their offspring, they have bigger maternity certainty because they themselves have carried out the child. However, males can never have 100% paternal certainty and therefore risk investing resources and time in offspring that is genetically unrelated. Evolutionary psychology views jealousy as an adaptive response to this problem.
Application of Trivers' theory in real life
Trivers' theory has been very influential as the predictions it makes correspond to differences in sexual behaviors of men and women, as demonstrated by a variety of research. Cross-cultural study from Buss (1989) shows that males are tuned into physical attractiveness as it signals youth and fertility and ensures male reproductive success, which is increased by copulating with as many fertile females as possible. Women on the other hand are tuned into resources provided by potential mates, as their reproductive success is increased by ensuring their offspring will survive, and one way they do so is by getting resources for them. Alternatively, another study shows that men are more promiscuous than women, giving further support to this theory. Clark and Hatfield[29] found that 75% of men were willing to have sex with a female stranger when propositioned, compared to 0% of women. On the other hand, 50% of women agreed to a date with a male stranger. This suggests males seek short-term relationships, while women show a strong preference for long-term relationships.
However, these preferences (male promiscuity and female choosiness) can be explained in other ways. In Western cultures, male promiscuity is encouraged through the availability of pornographic magazines and videos targeted to the male audience. Alternatively, both Western and Eastern cultures discourage female promiscuity through social checks such as slut-shaming.
PIT (Parental Investment Theory) also explains patterns of sexual jealousy. Males are more likely to show a stress response when imagining their partners showing sexual infidelity (having sexual relations with someone else), and women showed more stress when imagining their partner being emotionally unfaithful (being in love with another woman). PIT explains this, as woman's sexual infidelity decreases the male's paternal certainty, thus he will show more stress due to fear of cuckoldry. On the other hand, the woman fears losing the resources her partner provides. If her partner has an emotional attachment to another female it's likely that he won't invest into their offspring as much, thus a greater stress response is shown in this circumstance.
A heavy criticism of the theory comes from Thornhill and Palmer's analysis of it in A Natural History of Rape: Biological Bases of Sexual Coercion, as it seems to rationalise rape and sexual coercion of females. Thornhill and Palmer claimed rape is an evolved technique for obtaining mates in an environment where women choose mates. As PIT claims males seek to copulate with as many fertile females as possible, the choice women have could result in a negative effect on the male's reproductive success. If women didn't choose their mates, Thornhill and Palmer claim there would be no rape. This ignores a variety of sociocultural factors, such as the fact that not only fertile females are raped – 34% of underage rape victims are under 12, which means they are not of fertile age, thus there is no evolutionary advantage in raping them. 14% of rapes in England are committed on males, who cannot increase a man's reproductive success as there will be no conception. Thus, what Thornhill and Palmer called an 'evolved machinery' might not be very advantageous.
Versus sexual strategies
Trivers' theory overlooks that women do have short-term relationships such as one-night stands, while not all men behave promiscuously. An alternative explanation to PIT (Parental Investment Theory) and mate preferences would be Buss and Schmitt's sexual strategies theory. SST argues that both sexes pursue short-term and long-term relationships, but seek different qualities in their short- and long-term partners. For a short-term relationship women will prefer an attractive partner, but in a long-term relationship they might be willing to trade-off that attractiveness for resources and commitment. On the other hand, men might be accepting of a sexually willing partner in a short-term relationships, but to ensure their paternal certainty they will seek a faithful partner instead.
https://en.wikipedia.org/wiki/Parental_investment#Trivers'_parental_investment_theory
Sexual Strategies Theory - An Evolutionary Perspective on Human Mating
Sexual strategies theory is based on sexual selection theory. It proposes that humans have evolved a list of different mating strategies, both short-term and long-term, that vary depending on culture, social context, parental influence, and personal mate value (desirability in the “mating market”).
In its initial formulation, sexual strategies theory focused on the differences between men and women in mating preferences and strategies (Buss & Schmitt, 1993). It started by looking at the minimum parental investment needed to produce a child. For women, even the minimum investment is significant: after becoming pregnant, they have to carry that child for nine months inside of them. For men, on the other hand, the minimum investment to produce the same child is considerably smaller—simply the act of sex.
These differences in parental investment have an enormous impact on sexual strategies. For a woman, the risks associated with making a poor mating choice is high. She might get pregnant by a man who will not help to support her and her children, or who might have poor-quality genes. And because the stakes are higher for a woman, wise mating decisions for her are much more valuable. For men, on the other hand, the need to focus on making wise mating decisions isn’t as important. That is, unlike women, men 1) don’t biologically have the child growing inside of them for nine months, and 2) do not have as high a cultural expectation to raise the child. This logic leads to a powerful set of predictions: In short-term mating, women will likely be choosier than men (because the costs of getting pregnant are so high), while men, on average, will likely engage in more casual sexual activities (because this cost is greatly lessened). Due to this, men will sometimes deceive women about their long-term intentions for the benefit of short-term sex, and men are more likely than women to lower their mating standards for short-term mating situations.
An extensive body of empirical evidence supports these and related predictions (Buss & Schmitt, 2011). Men express a desire for a larger number of sex partners than women do. They let less time elapse before seeking sex. They are more willing to consent to sex with strangers and are less likely to require emotional involvement with their sex partners. They have more frequent sexual fantasies and fantasize about a larger variety of sex partners. They are more likely to regret missed sexual opportunities. And they lower their standards in short-term mating, showing a willingness to mate with a larger variety of women as long as the costs and risks are low.
However, in situations where both the man and woman are interested in long-term mating, both sexes tend to invest substantially in the relationship and in their children. In these cases, the theory predicts that both sexes will be extremely choosy when pursuing a long-term mating strategy. Much empirical research supports this prediction, as well. In fact, the qualities women and men generally look for when choosing long-term mates are very similar: both want mates who are intelligent, kind, understanding, healthy, dependable, honest, loyal, loving, and adaptable.
Nonetheless, women and men do differ in their preferences for a few key qualities in long-term mating, because of somewhat distinct adaptive problems. Modern women have inherited the evolutionary trait to desire mates who possess resources, have qualities linked with acquiring resources (e.g., ambition, wealth, industriousness), and are willing to share those resources with them. On the other hand, men more strongly desire youth and health in women, as both are cues to fertility. These male and female differences are universal in humans. They were first documented in 37 different cultures, from Australia to Zambia (Buss, 1989), and have been replicated by dozens of researchers in dozens of additional cultures (for summaries, see Buss, 2012).
As we know, though, just because we have these mating preferences (e.g., men with resources; fertile women), people don't always get what they want. There are countless other factors which influence who people ultimately select as their mate. For example, the sex ratio (the percentage of men to women in the mating pool), cultural practices (such as arranged marriages, which inhibit individuals’ freedom to act on their preferred mating strategies), the strategies of others (e.g., if everyone else is pursuing short-term sex, it’s more difficult to pursue a long-term mating strategy), and many others all influence who we select as our mates.
Sexual strategies theory—anchored in sexual selection theory— predicts specific similarities and differences in men and women’s mating preferences and strategies. Whether we seek short-term or long-term relationships, many personality, social, cultural, and ecological factors will all influence who our partners will be.
https://nobaproject.com/modules/evolutionary-theories-in-psychology
Sexual Strategies Theory - David M. Buss & David P. Schmitt
This article proposes a contextual-evolutionary theory of human mating strategies. Both men and women are hypothesized to have evolved distinct psychological mechanisms that underlie short-term and long-term strategies. Men and women confront different adaptive problems in short-term as opposed to long-term mating contexts. Consequently, different mate preferences become activated from their strategic repertoires. Nine key hypotheses and 22 predictions from Sexual Strategies Theory are outlined and tested empirically. Adaptive problems sensitive to context include;
sexual accessibility, fertility assessment, commitment seeking and avoidance, immediate and enduring resource procurement, paternity certainty, assessment of mate value, and parental investment.
Discussion summarizes 6 additional sources of behavioral data, outlines adaptive problems common to both sexes, and suggests additional contexts likely to cause shifts in mating strategy...
Précis of Sexual Strategies Theory
1. In human evolutionary history, both men and women have pursued short-term and long-term matings under certain conditions where the reproductive benefits have outweighed the costs.
2. Different adaptive problems must be solved when pursuing a short-term sexual strategy as opposed to pursuing a long-term sexual strategy.
3. Because of a fundamental asymmetry between the sexes in minimum levels of parental investment, men devote a larger proportion of their total mating effort to short-term mating than do women.
4. Because the reproductive opportunities and reproductive constraints differ for men and women in these two contexts, the adaptive problems that women must solve when pursuing each strategy are different from those that men must solve, although some problems are common to both sexes.
5. Men historically have been constrained in their reproduc-tive success primarily by the number of fertile women they can inseminate. This reproductive constraint on men can be sepa-rated into four relatively distinct problems that men historically had to solve to effectively pursue a short-term mating strategy: (a) the problem of partner number, (b) the problem of identify-ing which women are sexually accessible, (c) the problem of identifying which women are fertile, and (d) the problem of minimizing commitment and investment.
6. Reproductive constraints on men can be separated into four relatively distinct problems that men historically had to solve to effectively pursue a long-term mating strategy: (a) the problem of identifying reproductively valuable women, (b) the problem of ensuring certainty in paternity, (c) the problem of identifying women with good parenting skills, and (d) the prob-lem of identifying women who are willing and able to commit to a long-term mating relationship.
7. Women historically have been constrained in their repro-ductive success not by the number of men they can gain sexual access to but rather primarily by the quantity and quality of the external resources that they can secure for themselves and their children and perhaps secondarily by the quality of the man's genes.
8. These reproductive constraints can be separated into two distinct problems that women historically had to solve to effec-tively pursue a short-term mating strategy: (a) the problem of immediate resource extraction and (b) the problem of assessing prospective long-term mates.
9. These reproductive constraints can be separated into dis-tinct adaptive problems women historically had to solve to ef-fectively pursue a long-term mating strategy: (a) the problem of identifying men who have the ability to invest resources in her and her children on a long-term basis, (b) the problem of identi-fying men who show a willingness to invest resources in her and her children on a long-term basis, (c) the problem of identifying men with good parenting skills, (d) the problem of identifying men who are willing and able to commit to a long-term rela-tionship, and (e) the problem of identifying men who are able and willing to protect them from aggressive conspecifics (see Table 1).
10. Men and women have evolved distinct psychological mechanisms that function to solve the adaptive problems con-fronted to effectively pursue short-term and long-term matings.
11. These psychological mechanisms and their behavioral manifestations, combined with the temporal contexts in which each set is activated, constitute the evolved sexual strategies of men and women. Strategies are defined as evolved solutions to adaptive problems, with no consciousness or awareness on the part of the strategist implied.
Sexual Strategies Theory - An Evolutionary Perspective on Human Mating
- David M. Buss & David P. Schmitt
https://www.researchgate.net/publication/14715297_Sexual_Strategies_Theory_An_Evolutionary_Perspective_on_Human_Mating
Evolutionary Psychology: The New Science of the Mind 6th Edition by David Buss https://www.amazon.com/Evolutionary-Psychology-New-Science-Mind/dp/1138088617/
Summary: Sperm is plentiful-evolutionary it makes sense for males to try and impregnate as many females as possible. Eggs are more valuable-evolutionarily makes more sense for females to be choosy when it comes to mating, as they are the ones investing the time and effort into the offspring.
More Sexual Strategies Theory - Older Versions & Unsorted
THE DOUBLE STANDARD OF AGING
Men's physical attractiveness to women declines with age, but the decline is generally less steep than that of women to men. In what might be called the second cardinal rule of dating, men want partners who are a year or two younger than they are, while women, in general, want to date older men. As men age, they want women who are increasingly younger than they are. A man of forty, for example, is likely to want a partner who is ten years younger. Why?
The most fundamental reason relates to limitation of women's ability to conceive children with advancing years. Fertility reaches a high point in the early twenties and stays on a plateau until the age of thirty-five, after which it declines sharply. Natural selection would have caused men to select fertile women as wives since those who were attracted to women over fifty would have left no offspring to carry on their unusual taste. However, men see women as more attractive at twenty than at forty. This is right at the beginning of their most fertile phase in the life span.
Men are thus most attracted to women who are at the beginning of their reproductive career. If a man marries a woman of this age, then he has the potential of giving her all of her children and thereby hitting the reproductive jackpot. Natural selection has thus favored men who are attracted to younger fertile women rather than older fertile women. For this reason, the perception of youthfulness is critical to the physical attractiveness of women. This helps explain the success of the cosmetics industry, as women attempt to conceal signs of aging and try to appear younger and more attractive.
Men reach the peak of their physical attractiveness to women in the late teens or early twenties. However, as they grow older, they acquire social status and wealth, which enhances the value of the overall package as far as a marriage partner is concerned. Although men deteriorate with age, their physical appearance is less critical to their overall attractiveness. One important cue to feminine youthfulness that plays an important role in women's physical attractiveness is their bodily shape.
SELXUAL SELECTION AND THE HOURGLASS FIGURE
The body shapes of men and women are sexually selected traits, analogous to the plumage of the peacock. Strange as it might seem, this conclusion is supported by much compelling evidence. To begin with, feminine curves emerge around puberty, just like the colorful train of the peacock (see fig. 2). They are produced by the same mechanism, a surge in production of sex hormones. A surge of the sex hormone estrogen stimulates the filling of fat cells located away from the waist. The "loudness" of the signal (i.e., the size of the sex difference) diminishes with age. In the same way, the greater height of men, their broader shoulders, their deeper voices, and their greater upper-body musculature are due to the growth spurt produced by a surge in testosterone production at puberty.
Both sexes agree that women with "hourglass figures" are sexy and attractive (see fig. 3). This contrasts with the attractive male body. In sexy men, there is little difference between the hip and waist dimensions, the torso is moderately muscled, and the shoulders are broad. The attractiveness of an hourglass figure for women is a constant across cultures and across time, although the amount of curvature considered desirable varies greatly in different countries and at different times within a society.
Scientists assess the curvaceousness of the human body using a statistic known as the waist/hip ratio. A small waist/hip ratio is equivalent to a highly curvaceous body. Highly attractive women, such as Miss Americas, have a waist/hip ratio of about 0.67 (the ratio produced by a waist of 24" and hips of 36", for example). The normal range for women is 0.67-0.80, whereas the normal range for men is 0.85-0.95. Lack of an overlap between the male and the female range means that body shape is a highly predictable sex difference.
The intensity of the signal (i.e., the size of the sex difference) declines with age due to a change in hormone production. If you are on the beach and spot a couple strolling away from you in the distance, distinguishing the silhouette of the man from the woman will be very easy if the couple is in their twenties, but much more difficult if they are in their fifties.
One distinguishing characteristic of the peacock's tail is that it interferes with movement. Similarly, storage of fat away from the waist is not mechanically efficient. It makes more sense to store fat close to the center of gravity, in the abdomen. Highly curvaceous women are at a distinct disadvantage in sports and rarely win Olympic medals-for example, in events requiring agility and speed, such as basketball and running. This is not to claim that curvaceous women cannot be very athletic. Some are, but when they compete at the highest level, they experience a mechanical disadvantage because weight stored away from the center of gravity introduces turning forces that use up energy.
Just as peahens are attracted to an extremely colorful mate, so extremely attractive women are at an extreme of the range for curvaceousness. Beauty contest winners cluster at the curvaceous extreme of 0.67 compared to the normal range for women of 0.67-0.80.
Perhaps the most important and compelling point of similarity is that curvaceous women, like showy peacocks, have superior immune systems. According to recent research ot'Devendra Singh, an evolutionary psychologist at the University of Texas at Austin, college-aged women and men agree that curvaceous women (whether of normal weight, underweight, or overweight) are more attractive, healthier, and more capable of producing children than less curvaceous women. What makes these findings really interesting is that they are borne out by medical data. Women with low waist/hip ratio (i.e., with a curvaceous build) not only have less difficulty becoming pregnant, they are also healthier in terms of a lower incidence of many illnesses. Women with relatively noncurvaceous bodies are at a higher risk for gall bladder disease, some cancers, diseases of the heart and circulatory system, and for diabetes. (It is important to realize that a curvaceous body is different from an obese one: curvaceous women store fat away from the abdomen whereas obese women usually have thick fat deposits around their middle which pose major health risks.) Noncurvaceous women are also more prone to behavioral disorders such as anxiety and drug abuse. (It is true that some drug addictions can cause people to lose weight, which might make them less curvaceous, but the finding applies equally for alcoholism, which can have the opposite effect.) Less curvaceous women are more likely to be admitted to psychiatric hospitals for depression and other psychopathologies. They also have higher mortality rates. The health consequences of body shape in men have received less attention because the waist/hip ratio is not routinely measured for medical records and is thus unavailable to researchers. Women are at their most curvaceous in early maturity, and one reason that men are attracted to women with sexy bodies is that this is a cue to youthfulness. Exceptionally attractive women have youthful facial dimensions that make them seem more attractive than they really are.
EXAGGERATING YOUTH
Men are very sensitive to age cues, since a woman's age places limitations on her ability to produce children. It is true that men may be motivated by opportunities for sexual intercourse rather than opportunities for reproducing, but natural selection has designed them to want sex with fertile women. The sex difference in the importance of youthfulness to physical attractiveness explains why women are much more interested in using makeup to make them seem young and healthy than men are.
Highly attractive women, such as film actresses, often preserve their good looks into old age. The impression of youthfulness is so powerfully conveyed by the design of their faces that seeing them as old is difficult. When you see Candice Bergen, now well into her fifties, for example, your response is likely to be, "What a stunningly beautiful woman!" rather than "Candice seems to be well into her fifties."
Highly attractive women's faces mimic some facial proportions normally found only in young girls. This is not just true of our own culture with its exaltation of all things youthful, but in Japan and other countries. The extent of this phenomenon can be grasped from the fact that attractive male faces tend to have large chins, a feature associated with age and maturity, whereas attractive female faces have reasonably small chins and therefore resemble the faces of children. Similarly, small noses contribute to the attractiveness of women's faces, but the size of the nose is unrelated to attractiveness of men.
Other youthful traits that people see as attractive in women (but not men) in different cultures include dainty hands and small feet. These are not just smaller in women because they have shorter stature, but they are proportionately smaller. Small feet were such a critical feature of attractiveness in China that parents kept their daughters' artificially small through the hideous practice of foot binding. From a biological perspective, small chins, feet, and hands are attributable to low levels of testosterone, which promotes bone growth. Since testosterone reduces female fertility, they are thus an outward sign of a hormonal profile conducive to high fertility in women.
Victor Johnson, an evolutionary psychologist working at the University of New Mexico at Las Cruces, has collected other evidence that shows the extensive effects of sexual selection on the female face. Johnson and his associate used a computer program that allowed people to "evolve" their perfect faces over many "generations." One striking aspect of the perfect faces was that many dimensions were typical of much younger faces. Although people estimated the age of the perfect faces as close to twenty-five years, on average, the proportions of the lips (their fullness) was characteristic of fourteen-year-old faces, while the length of the face, from eyes to chin, was shortened to that typical of an eleven-year-old.
Just as male peacocks have competed with each other to be very colorful, so women have competed to exaggerate the impression of youthfulness and health conveyed by their faces, as already noted. The reproductive significance of youthfulness for women helps to explain why they are prepared to spend a lot of money on cosmetics that create an impression of youth and health. Expensive creams promise to remove wrinkles, those telltale signs of aging, and to restore the healthy glow of youthful skin. Lipstick exaggerates the hue and enhances the fullness of the lips, making them seem younger. Shampooing and brushing make the hair seem more luxuriant and healthy (see fig. 4). Women use a whole range of products to enhance the apparent size and brightness of their eyes in an attempt to recreate the breathless and starry-eyed innocence of youth. What women do individually with makeup is analogous to what natural selection has been doing for hundreds of generations.
Humans are unusual in that both sexes evolved physically attractive traits through sexual selection. Human beards, for example, advertise biological quality in the same way that the gaudy plumage of the peacock does. This implies that both men and women compete among themselves for desirable mates. Handsome men and beautiful women are healthier and more fertile than their romantic competitors and transmit these qualities to children. Advertisement of biological quality through evolved bodily signals is not the only form that reproductive competition takes. People compete for marriage partners by being friendly and kind, and thereby advertising the qualities that are desirable in a long-term partnership. Men enhance their sexual attractiveness by competing for social status. This competition can take the form of reckless aggression, particularly in young men.
Chapter Three Loves Labors Dating Competition and Aggression
During the breeding season, male robins experience a rise in testos- terone production that makes them more aggressive. They are highly territorial and defend their home turf by mounting a vigorous physical assault on intruding male robins. The song of the male serves as a warning to rivals that this space is taken and thereby inhibits intruders.
Singing, like fighting, is controlled by testosterone. This phenomenon has been demonstrated by injecting female songbirds with testosterone. Female songbirds normally do not sing, but they will do so after they have been treated with the male hormone.
The increased aggression of males during the breeding season is an adaptation that helps them succeed in the struggle for access to reproductive females. Their testosterone surge primes them to defend a territory by singing and fighting. The territory is of critical importance for reproductive success. Males that cannot defend a breeding territory do not acquire mates.
Human males do not have a breeding season, of course, but they compete most vigorously for mates when they are young, and when their testosterone levels are highest. Young men do not have breeding territories either, but they fight over something that plays the same role, namely, high social status among peers. Young men who have low social status-who are not "cool"-become the butt of jokes and are often viewed by girls as undesirable dating part- ners. Concern over "face," or status, is at the root of much appar- ently senseless violence between young men.
The Science of Romance - by Nigel Barber
http://www.amazon.com/exec/obidos/tg/detail/-/1573929700/
A male can get awav with a few minutes of copulation and a tablespoon of semen, but a female carries an offspring for months inside her body and nourishes it before and after it is born. As they say of the respective contributions of the chicken and the pig to eggs and bacon, the first is involved, but the second is committed. Since it takes one member of each sex to make a baby, access to females is the limiting resource for males in reproduction. For a male to maximize the number of his descendants, he should mate with as many females as possible; for a female to maximize the number of her descendants, she should mate with the best-quality male available.
This explains the two widespread sex differences in many species in the animal kingdom: males compete, females choose; males seek quantity, females quality.
Humans are mammals, and our sexual behavior is consistent with our Linnaean class. Donald Symons sums up the ethnographic record on sex differences in sexuality:
"Among all peoples it is primarily men who court, woo, proposition, seduce, employ love charms and love magic, give gifts in exchange for sex, and use the services of prostitutes."
Among Western peoples, studies have shown that men seek a greater number of sexual partners than women, are less picky in their choice of a short-term partner, and are far more likely to be customers for visual pornography. But the male of Homo sapiens differs from the male of most other mammals in a crucial way: men invest in their offspring rather than leaving all the investing to the female. Though deprived of organs that can siphon nutrients directly into his children, a man can help them indirectly by feeding, protecting, teaching, and nurturing them. The minimum investments of a man and a woman are still unequal, because a child can be born to a single mother whose husband has fled but not to a single father whose wife has fled. But the investment of the man is greater than zero, which means that women are also predicted to compete in the mate market, though they should compete over the males most likely to invest (and the males with the highest genetic quality) rather than the males most willing to mate.
The genetic economics of sex also predicts that both sexes have a genetic incentive to commit adultery, though for partly different reasons. A philandering man can have additional offspring by impregnating women other than his wife. A philandering woman can have better offspring by conceiving a child by a man with better genes than her husband while having her husband around to help nurture the child. But when a wife gets the best of both worlds from her affair, the husband gets the worst of both worlds, because he is investing in another man's genes that have usurped the place of his own. We thus get the flip side of the evolution of fatherly feelings: the evolution of male sexual jealousy, designed to prevent his wife from having another man's child. Women's jealousy is tilted more toward preventing the alienation of a man's affections, a sign of his willingness to invest in another woman's children at the expense of her own.
The biological tragedy of the sexes is that the genetic interests of a man and a woman can be so close that they almost count as a single organism, but the possibilities for their interests to diverge are never far away. The biologist Richard Alexander points out that if a couple marry for life, are perfectly monogamous, and favor their nuclear family above each spouse's extended family, their genetic interests are identical, tied up in the single basket containing their children. Under that idealization, the love between a man and a woman should be the strongest emotional bond in the living world-"two hearts beating as one"-and of course for some lucky couples it is. Unfortunately, the ifs in the deduction are big ifs. The power of nepotism means that spouses are always being tugged apart by in-laws and, if there are any, by stepchildren. And the incentives of adultery mean that spouses can always be tugged apart by cuckolds and home-wreckers. It is no surprise to an evolutionary biologist that infidelity, stepchildren, and in-laws are among the main causes of marital strife... - Steven Pinker
The Blank Slate: The Modern Denial of Human Nature
https://www.amazon.com/Blank-Slate-Modern-Denial-Nature/dp/0142003344
Men's bargaining position is based on social status and wealth. In
subsistence hunter-gatherer societies, such as the Siriono of Brazil, a
man's sexual attractiveness to women is based largely on his reputation as a
successful hunter. In modem societies, women are more interested in a man's
education and income level than his hunting ability, but this concern
represents the same underlying need to find a mate who will be a good
provider of food and other economic goods.
Even though modern women sometimes
earn more than most men, their evolved
psychology has not changed. They are
still attracted to successful men...
In early subsistence societies, as well as more recent ones, women were
constantly pregnant, breast-feeding, or caring for children or all three.
This would have interfered with their ability to work and acquire surplus
food or property. Today, the birth rate is much lower due to the use of
effective birth control techniques. Moreover, children spend the day in
daycare or with babysitters, which frees their mothers for full-time
occupations. Successful rearing of children among our hunter-gatherer
ancestors was a cooperative enterprise in which men contributed to feeding,
sheltering, carrying, protecting, and caring for their offspring. The
critical importance of fathers for the survival of their children is
demonstrated by the Ache of Paraguay, who are more than twice as likely to
die during childhood if they lose their father.
Women, in general, have evolved to compete for husbands with social status
and wealth because these are reliable cues to the ability to protect and
care for children.
Physically attractive women (as assessed from high school yearbook
photographs) are much more likely to marry. They also marry up the social
ladder, finding husbands that are wealthier than their parents; the same,
however, is not true of men. Physically attractive women move up into
wealthy elites through marriage, while physically attractive men do not.
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Effects of Women's Personal Resources on Mate Preferences
Context Effects on Women’s Mating Strategies
From an evolutionary perspective, preferences are not predicted to operate blindly, oblivious to context or condition. Just as human desires for particular foods (e.g., ripe fruit) depend on context (e.g., whether one is hungry or full), women’s preferences in a mate also depend in part on relevant contexts. Several contexts have been explored: the magnitude of resources a woman already has prior to her search for a mate, the degree of economic inequality between the genders across cultures, other women’s apparent attraction to a man, the temporal context of mating (committed versus casual mating), and the woman’s mate value.
Effects of Women’s Personal Resources on Mate Preferences
An alternative explanation has been offered for the preferences of women for men with resources—variously called the structural powerlessness, sex role socialization, or gender economic inequality hypothesis (Buss & Barnes, 1986; Eagly & Wood, 1999). According to this view, because women are typically excluded from power and access to resources, which are largely controlled by men, women seek mates who have power, status, and earning capacity. Women try to marry upward in socioeconomic status because this provides their primary channel for gaining access to resources. Men do not value economic resources in a mate as much as women do because they already have control over these resources and because women have fewer resources anyway.
The society of Bakweri, from Cameroon in West Africa, provides one test case of this hypothesis by illustrating what happens when women have real power (Ardener, Ardener, & Warmington, 1960). Bakweri women hold greater personal and economic power because they have more resources and are in scarcer supply than men. Women secure resources not only through their own labors on plantations but also from casual sex, which is a lucrative source of income. There are roughly 236 men for every hundred women, an imbalance that results from the continual influx of men from other areas of the country to work on the plantations. Because of the extreme imbalance in numbers of the sexes, women have considerable latitude to exercise their choice in a mate. Women thus have more money than men and more potential mates to choose from. Yet Bakweri women persist in preferring mates with resources. Wives often complain about receiving insufficient support from their husbands. Lack of sufficient economic provisioning is the reason most frequently cited by women for divorce. Bakweri women change husbands if they find a man who can offer them more resources and pay a larger bride-price. When women are in a position to fulfill their evolved preference for a man with resources, they do so. Having personal control of economic resources apparently does not negate this mate preference.
Professionally and economically successful women in the United States also value resources in men. One study identified women who were financially successful, as measured by their salary and income, and contrasted their preferences in a mate with those of women with lower salaries and income (Buss, 1989a). The financially successful women were well educated, tended to hold professional degrees, and had high self-esteem. Successful women turned out to place an even greater value than less professionally successful women on mates who have professional degrees, high social status, and greater intelligence and who are tall, independent, and self-confident. Women’s personal income was positively correlated with the income they wanted in an ideal mate (+.31), the desire for a mate who is a college graduate (+.29), and the desire for a mate with a professional degree (+.35). Contrary to the sex role hypothesis, these women expressed an even stronger preference for high-earning men than did women who are less financially successful. Professionally successful women, such as medical and law students, also place heavy importance on a mate’s earning capacity (Wiederman & Allgeier, 1992).
Cross-cultural studies consistently find small but positive relationships between women’s personal access to economic resources and preferences for mates with resources. A study of 1,670 Spanish women seeking mates through personal advertisements found that women who have more resources and status were more likely to seek men with resources and status (Gil-Burmann, Pelaez, & Sanchez, 2002). A study of 288 Jordanians found that both women and men with high socioeconomic status place more, not less, value on the mate characteristics of having a college graduate degree and being ambitious-industrious (Khallad, 2005). A study of 127 individuals from Serbia concluded:
“The high status of women correlated positively with their concern with a potential mate’s potential socio-economic status, contrary to the prediction of the socio-structural model” (Todosijevic, Ljubinkovic, & Arancic, 2003, p. 116). An internet study of 1,851 women, examining the effects of women’s actual income, found that “wealthier women prefer good financial prospects over physical attractiveness” (Moore, Cassidy, Smith, & Perrett, 2006, p. 201).
Other large-scale cross-cultural studies continue to falsify or fail to support the structural powerlessness hypothesis, or social role theory as it is sometimes called (Lippa, 2009; Schmitt, 2012; Schmittet al., 2009).
Buss, D. M., & Barnes, M. F. (1986). Preferences in human mate selection. Journal of Personality and Social Psychology, 50, 559–570.
Eagly, A. H., & Wood, W. (1999). The origins of sex differences in
human behavior: Evolved dispositions or social roles?
American Psychologist, 54, 408–423.
Ardener, E. W., Ardener, S. G., & Warmington, W. A. (1960).
Plantation and village in the Cameroons. London: Oxford University
Press.
Buss, D. M. (1989a). Sex differences in human mate preferences:
Evolutionary hypotheses testing in 37 cultures. Behavioral and Brain
Sciences, 12, 1–49.
Wiederman, M. W., & Allgeier, E. R. (1992). Gender differences in mate selection criteria: Sociobiological or socioeconomic explanation? Ethology and Sociobiology, 13, 115–124.
Gil-Burmann, C., Pelaez, F., & Sanchez, S. (2002). Mate choice differences according to sex and age: An analysis of personal advertisements in Spanish newspapers. Human Nature, 13, 493–508.
Khallad, Y. (2005). Mate selection in Jordan: Effects of sex, socio-economic status, and culture. Journal of Social and Personal Relationships, 22, 155–168.
Todosijevic, B., Ljubinkovic, S., & Arancic, A. (2003). Mate selection criteria: A trait desirability assessment study of sex differences in Serbia. Evolutionary Psychology, 1, 116–126.
Moore, F. R., Cassidy, C., Smith, M. J. L., & Perrett, D. I. (2006a). The effects of female control of resources on sex-differentiated mate preferences. Evolution and Human Behavior, 27, 193–205.
Lippa, R. A. (2009). Sex differences in sex drive, sociosexuality, and height across 53 nations: Testing evolutionary and social structural theories. Archives of Sexual Behavior, 38, 631–651.
Schmitt, D. P. (2012). When the difference is in the details: A critique of Zentner and Mtura “Stepping out of the caveman’s shadow: Nations’ gender gap predicts degree of sex differentiation in mate preferences”. Evolutionary Psychology, 10, 720–726.
Schmitt, D. P., Youn, G., Bond, B., Brooks, S., Frye, H., Johnson, S., Klesman, J., Peplinski, C., Sampias, J., Sherrill, M., & Stoka, C. (2009). When will I feel love? The effects of culture, personality, and gender on the psychological tendency to love. Journal of Research in Personality, 43, 830–846.
Evolutionary Psychology: The New Science of the Mind - 6th Ed - by David
Buss
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