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I would like to thank @abaddon79 for showing me a few Wikipedia articles that I thought were interesting and decided to look further into. Without that initial push, this thread would not have been written. What follows is an attempt to understand why, across species and through time, females tend to be more selective than males, and how that difference shapes both animal behavior and human society.
I begin with what I take to be foundational: the work deriving from Angus J. Bateman and its descendants. His experiment on Drosophila melanogaster, commonly known as the fruit fly, showed that male reproductive success rises with number of mates, whereas female reproductive success levels off after relatively few mates. From this he derived what is now called Bateman's principle: the sex with greater variance in reproductive success faces stronger sexual selection pressure, while the sex with lower variance can afford to be more selective.
One study I found particularly persuasive in support of this principle examined a highly polygynous human population (that is, a population in which males may have multiple female partners) and concluded that "variance in male reproductive success is significantly higher than variance in female reproductive success" (Brown, Laland, & Borgerhoff Mulder, 2009).
This finding implies that males experience far greater disparity in reproductive outcomes, with a few achieving many matings while most achieve few or none, whereas females tend to reproduce at more comparable rates. From this I infer that females are the limiting reproductive resource and thus have more room to be selective.
Now, having established that females are the limiting reproductive resource, I turn to the biological process that explains why. In every sexually reproducing species, the two sexes contribute differently to the formation of offspring; females produce relatively few large gametes that contain the nutrients necessary to support early development, while males produce an enormous number of small gametes whose primary function is to deliver genetic material. This difference, known as anisogamy, forms the basis of what Robert Trivers, an American evolutionary biologist known for his work on social evolution and parental investment, later described as parental investment theory: because females invest more energy and face greater risk in producing and raising offspring, they lose more from a poor mating choice. It follows that selection favors choosiness in females and competitiveness in males because females risk losing more reproductive energy and offspring survival from a poor mating choice, whereas males stand to gain more reproductive success from securing additional mates.
What makes this difference in reproductive investment between males and females so important is that it explains why competition among males takes so many visible forms. Once females become the limiting resource, males must secure access to them by any means that increases their relative success. The evolutionary response has been the development of traits that attract attention or outcompete rivals, a process first described by Ronald Fisher, a British geneticist and statistician, as the runaway model of sexual selection: when females prefer a certain male characteristic, and that preference itself is heritable, both the trait and the preference intensify across generations.
Over time, this feedback loop can exaggerate male features to such extremes that they no longer aid survival and may even hinder it: the peacock's long, brightly patterned tail attracts females but slows flight and increases visibility to predators; the Irish elk's enormous antlers, as noted to me by @abaddon79, gave males an advantage in attracting mates and intimidating rivals but required immense energy and nutrition, and when environmental changes reduced food quality, the continued female preference for larger antlers became maladaptive, contributing to the species' extinction; and the bright orange and iridescent patches on male guppies increase female interest in mating but also make males easier for visual predators to detect.
Up to this point, the focus has been on animals, but I imagine you guys have been waiting for the part that concerns us (that is, human beings), and it turns out that the same principles apply to humans more closely than most would like to admit. In nineteen eighty-nine, David Buss, an evolutionary psychologist at the University of Texas, conducted a cross-cultural study of over ten thousand participants across thirty-seven societies (Buss, 1989). In that study, Buss reported that women, regardless of geography or income, placed greater value on traits indicating resource acquisition, such as ambition, industriousness, and earning potential, while men placed greater value on youth and physical attractiveness, traits associated with fertility. Buss emphasized that these differences were consistent across cultures, suggesting that they arise from evolved sex-specific reproductive pressures.
Now, before you guys start complaining that physical appearance is the only thing that matters to women, or is at least the most important factor in what attracts women, I should clarify what more recent work shows. Buss's study described broad sex differences in stated preference across thirty seven cultures in nineteen eighty nine, but more recent studies measure actual choice.
In a study published in twenty seventeen, Madeleine A. Fugère and her colleagues Caitlynn Chabot, Kaitlyn Doucette, and Alita J. Cousins asked pairs of adult daughters and the mothers of those daughters to judge men who varied in both physical attractiveness and described traits such as ambition, kindness, and reliability. The women and the mothers reported, in the abstract, that qualities like ambition and kindness mattered more than physical attractiveness; however, when the women and their mothers had to select which men were desirable partners, both the women and the mothers preferred the attractive and moderately attractive men, and unattractive men were never chosen as more desirable partners even when the unattractive men were described as having the most desirable personality profiles (Fugère et al., 2017).
Fugère and her coauthors concluded that "a minimum level of physical attractiveness is a necessity for both women and their mothers and that when women and their parents state that other traits are more important than physical attractiveness, they assume potential mates meet a minimally acceptable standard of physical attractiveness."
At last, I think I have reached a point from which to draw the matter to a close. Because female reproduction requires greater biological investment and carries higher risk, women have evolved to be more selective in choosing mates. Men, by contrast, must compete to be chosen, developing and displaying traits that demonstrate fitness in their environment, such as status, resources, strength, or intelligence. Female fertility signals are largely biological and limited by age, while male desirability depends more on performance and achievement. In practical terms, women act as the gatekeepers of reproduction, and men as the petitioners.
I begin with what I take to be foundational: the work deriving from Angus J. Bateman and its descendants. His experiment on Drosophila melanogaster, commonly known as the fruit fly, showed that male reproductive success rises with number of mates, whereas female reproductive success levels off after relatively few mates. From this he derived what is now called Bateman's principle: the sex with greater variance in reproductive success faces stronger sexual selection pressure, while the sex with lower variance can afford to be more selective.
One study I found particularly persuasive in support of this principle examined a highly polygynous human population (that is, a population in which males may have multiple female partners) and concluded that "variance in male reproductive success is significantly higher than variance in female reproductive success" (Brown, Laland, & Borgerhoff Mulder, 2009).
This finding implies that males experience far greater disparity in reproductive outcomes, with a few achieving many matings while most achieve few or none, whereas females tend to reproduce at more comparable rates. From this I infer that females are the limiting reproductive resource and thus have more room to be selective.
Now, having established that females are the limiting reproductive resource, I turn to the biological process that explains why. In every sexually reproducing species, the two sexes contribute differently to the formation of offspring; females produce relatively few large gametes that contain the nutrients necessary to support early development, while males produce an enormous number of small gametes whose primary function is to deliver genetic material. This difference, known as anisogamy, forms the basis of what Robert Trivers, an American evolutionary biologist known for his work on social evolution and parental investment, later described as parental investment theory: because females invest more energy and face greater risk in producing and raising offspring, they lose more from a poor mating choice. It follows that selection favors choosiness in females and competitiveness in males because females risk losing more reproductive energy and offspring survival from a poor mating choice, whereas males stand to gain more reproductive success from securing additional mates.
What makes this difference in reproductive investment between males and females so important is that it explains why competition among males takes so many visible forms. Once females become the limiting resource, males must secure access to them by any means that increases their relative success. The evolutionary response has been the development of traits that attract attention or outcompete rivals, a process first described by Ronald Fisher, a British geneticist and statistician, as the runaway model of sexual selection: when females prefer a certain male characteristic, and that preference itself is heritable, both the trait and the preference intensify across generations.
Over time, this feedback loop can exaggerate male features to such extremes that they no longer aid survival and may even hinder it: the peacock's long, brightly patterned tail attracts females but slows flight and increases visibility to predators; the Irish elk's enormous antlers, as noted to me by @abaddon79, gave males an advantage in attracting mates and intimidating rivals but required immense energy and nutrition, and when environmental changes reduced food quality, the continued female preference for larger antlers became maladaptive, contributing to the species' extinction; and the bright orange and iridescent patches on male guppies increase female interest in mating but also make males easier for visual predators to detect.
Up to this point, the focus has been on animals, but I imagine you guys have been waiting for the part that concerns us (that is, human beings), and it turns out that the same principles apply to humans more closely than most would like to admit. In nineteen eighty-nine, David Buss, an evolutionary psychologist at the University of Texas, conducted a cross-cultural study of over ten thousand participants across thirty-seven societies (Buss, 1989). In that study, Buss reported that women, regardless of geography or income, placed greater value on traits indicating resource acquisition, such as ambition, industriousness, and earning potential, while men placed greater value on youth and physical attractiveness, traits associated with fertility. Buss emphasized that these differences were consistent across cultures, suggesting that they arise from evolved sex-specific reproductive pressures.
Now, before you guys start complaining that physical appearance is the only thing that matters to women, or is at least the most important factor in what attracts women, I should clarify what more recent work shows. Buss's study described broad sex differences in stated preference across thirty seven cultures in nineteen eighty nine, but more recent studies measure actual choice.
In a study published in twenty seventeen, Madeleine A. Fugère and her colleagues Caitlynn Chabot, Kaitlyn Doucette, and Alita J. Cousins asked pairs of adult daughters and the mothers of those daughters to judge men who varied in both physical attractiveness and described traits such as ambition, kindness, and reliability. The women and the mothers reported, in the abstract, that qualities like ambition and kindness mattered more than physical attractiveness; however, when the women and their mothers had to select which men were desirable partners, both the women and the mothers preferred the attractive and moderately attractive men, and unattractive men were never chosen as more desirable partners even when the unattractive men were described as having the most desirable personality profiles (Fugère et al., 2017).
Fugère and her coauthors concluded that "a minimum level of physical attractiveness is a necessity for both women and their mothers and that when women and their parents state that other traits are more important than physical attractiveness, they assume potential mates meet a minimally acceptable standard of physical attractiveness."
At last, I think I have reached a point from which to draw the matter to a close. Because female reproduction requires greater biological investment and carries higher risk, women have evolved to be more selective in choosing mates. Men, by contrast, must compete to be chosen, developing and displaying traits that demonstrate fitness in their environment, such as status, resources, strength, or intelligence. Female fertility signals are largely biological and limited by age, while male desirability depends more on performance and achievement. In practical terms, women act as the gatekeepers of reproduction, and men as the petitioners.
