Download The Descent of Sex: An Examination of Evolutionary

The Descent of Sex: An Examination of Evolutionary Mating Strategies, Its
Applications to The Human World, and The Implications on Gender Roles
Andrea Pace
0560530
ASCI*4020
Sofie Lachapelle
December 3, 2009
Introduction
The Descent of Man, and Selection in Relation to Sex, Charles Darwin’s second
significant book on evolutionary theory, presents the interesting concept of sexual
selection. This concept outlines the differences found between males and females in
regards to mating strategy and forces of selection. Sexual selection shows that the
differences between the sexes have an impact on reproductive fitness through the action
of obtaining mates (Freeman & Herron, 2007). When taken from a human perspective,
mate selection is believed to be controlled by evolved, possibly subconscious
mechanisms that have advanced in nature as a means of perpetuating the species
(Urbaniak & Kilmann, 2006). When the book was published in 1871 it seemed to confirm
the Victorian idea of men’s superiority to women. The book made use of its arguments to
capitalize on society’s opinions on women, and their role in a man’s world. But when
taken in a more modern context, the concepts provide a unifying theory of evolution that
can be applied to the evolution of human mating including a more balanced perspective
on male and female involvement. Recent studies done in the last decade or so have
attempted to explain sexual selection and its role today in human mating. For example
one can see parallels between female primates’ preference for males with good skin and
coat condition, as well as males who display caring interactions with present infants, and
the qualities one looks for in a significant other. These studies are able to support the idea
of a contemporary theory of sexual selection. However, there are always other possible
explanations for these results. Sexual behaviour can be affected by a variety of biological,
societal, and cultural factors. Each of these factors has the possibility to affect both males
and females in different ways (Fisher, 2009). This paper’s objective is to analyze sexual
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selection theory, using evolutionary psychology, in order to assess sex and gender
differences and the impact these theories has had on gender roles. This analysis will
include a description of the theory of sexual selection and how it applies in the animal
kingdom, a description of how the theory of sexual selection has been applied to the
human kingdom, the impact of this evolutionary theory on gender roles, and alternative
explanations for these mating strategies. This dissection of these theories and their
applications will rely heavily on evolutionary psychology, sociobiology, social role
theory, and feminist critique in order to create an all-encompassing perspective on the
subject matter.
Theory of Sexual Selection in the Animal Kingdom
Underlying Principles of Sexual Selection
As mentioned earlier, sexual selection states that the differences found between
the sexes have an influence on reproductive fitness, specifically through obtaining mates
(Freeman & Herron, 2007). Sexual selection theory predicts that sexual selection will act
more strongly on the sex that is less reproductively invested in order to increase this
species’ mating success (Freeman & Herron, 2007). The sex that is more strongly acted
upon by sexual selection will be more competitive, and the sex that is weakly acted upon
by sexual selection will be choosy (Freeman & Herron, 2007). The latter typically is
found to be a female species, and the former is more often a male species. The
competitive individual will compete for access to the opposite sex or for resources that
are required by the opposite sex (Freeman & Herron, 2007). Females are often the
choosier sex, being more discriminating when choosing a mate due to the fact that they
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are more reproductively invested. This is because a females eggs are much more
expensive to produce than the male sperm (Freeman & Herron, 2007). By being choosier,
they will engage in a courtship with the opposite sex. This courtship will offer evidence
of genetic quality of the male mate and also provide resources for the female and her
offspring (Freeman & Herron, 2007). Since males can produce large quantities of sperm
they are capable of fertilizing many females in rapid progression (Small, 1989). This
ability predicts that males are expected to compete in order to achieve reproductive
opportunities (Small, 1989). Competition can be described as being either intrasexual or
intersexual. In the case of intrasexual competition, competition occurs between members
of the same sex as a means of obtaining access to the opposite sex, or to resources. In
nature, these are often presented as features used to combat with members of the same
sex (Freeman & Herron, 2007). Intersexual competition is the evolution of behaviours
used by one sex to attract members of the opposite sex that are choosy. This presents
itself in nature as features or behaviours, such as beautiful and colourful plumage, that are
used to convince members of the opposite sex to mate (Freeman & Herron, 2007). There
are vast amounts of evidence to support these findings. One example is that female
drosophila were found to favour male mates who performed the appropriate courtship
behaviour (Small, 1989).
Mate Preferences Between the Sexes
Mate preferences between the sexes present themselves as varied. This is due to
the fact that males and females have varied levels of reproductive investment involved in
mating. As well, reproductive fitness is different depending on the sex of the species.
Specific characteristics are selected for in nature because they enhance the mating
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success of the particular species (Small, 1989). The other part of natural selection is
choice, which typically falls into the hands of the female species. Mate choice consists of
choosing individuals who display epigamic selection (adaptations that advance the union
of gametes) or all-aesthetic selection (adaptations of displayed characteristics) (Small,
1989). Darwin stated that, “Males are eager to mate with just about any female” (Small,
1989). As such, in nature, males basic mission is to compete for fertile females (Small,
1989). Females, being the choosier sex, have a more discriminating approach to mate
selection. Females display preferences for certain males. Female primates look for male
mates who display good genes, high status, novelty, familiarity, access to resources, and
qualities of parental care (Small, 1989). There are clear benefits for both the female and
her offspring when she displays particular tastes for mates as well as discriminating mate
selection. The power of female choice can be seen in the instance of runaway selection.
Females’ specific preferences will cause them to always choose the same type of mates.
This will result in male offspring similar to these male mates, and the propagation of
selection for these desired traits (Small, 1989). It should be noted that there are instances
in nature where males are the more invested sex (such as with seahorses, and Panamanian
poison arrow frogs) (Vandermassen, 2004). In this case, forces of sexual selection are
slightly different.
Promiscuity in Nature
Research often presents female species as monogamous and outlines the benefits
of such a mating strategy. However, there are many pieces of evidence to show the
benefits of having multiple mates. Females may mate with multiple males if the males in
that area are often sterile, or as a means of maximizing the offspring’s genetic diversity
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(Freeman & Herron, 2007). The “fertility back up hypothesis” states that females may
require sperm from multiple males in order to assure conception (Blaffer-Hrdy, 1986).
The “inferior cuckold hypothesis” states that females who have been paired with an
inferior male will seek genetically superior males when conception is likely (BlafferHrdy, 1986). The “diverse paternity hypothesis” states that females who are confronted
with unpredictable changes in the environment will produce clutches fathered by multiple
males in order to diversify the offspring (Blaffer-Hrdy, 1986). There are many examples
of this in nature. Female Savanna baboons initiate multiple and brief courtships (BlafferHrdy, 1986). Female chimpanzees often alternate between long-term courtships with one
mate as well as communal mating with other mates in the area (Blaffer-Hrdy, 1986).
The theory of sexual selection does indeed demonstrate that there are sex
differences between mating strategies, mate preference, and mate choice. All of which
are used as a method to increase reproductive fitness and success for the individual.
Theory of Sexual Selection As It Applies in the Human Kingdom
Underlying Principles of Human Mating Strategies
The theory of sexual selection stated in terms of the animal kingdom is relevant
and useful when examining human mating strategies as well. One sex, usually the male,
will compete with other males to gain mating access to the other sex (Vandermassen,
2004). He will compete by using threats, combat, or by showing off (Vandermassen,
2004). Thus, male ornamentation and competition for females evolved so females can
actively choose the strongest and best-ornamented males (Vandermassen, 2004).
According to sociobiological theory the two key players in human mating are the
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nurturing female (highly invested) and the competitive male (invests little) (Blaffer-Hrdy,
1986). The number of women he inseminates increases a man’s reproductive success,
therefore it is expected that men desire higher numbers of sexual partners (Urbaniak &
Kilmann, 2006). Therefore male’s reproductive success is limited by the number of fertile
females he is able to mate with (Vandermassen, 2004). On the other hand, female’s
reproductive success is limited by the time and energy that is required to raise offspring
(Vandermassen, 2004). This explains why males are more eager to mate with many
partners, and females are choosy when selecting a mate. Men attempt to increase their
fitness by allowing less time to pass before seeking a sexual partner, having a greater
desire for sexual variety, actively seeking short-term mating opportunities, and being
more competitive (Vandermassen, 2004). Women attempt to increase their fitness by
competing among other women for the features men find sexually attractive. They strive
to attain beauty, youth, and to be more nurturing (Vandermassen, 2004). Females are able
to maximize their fitness by being more discriminating (Archer, 1996). This strategy will
be more likely to ensure a male mate with good genes, resources, and parental skills
(Archer, 1996). Males are able to maximize their fitness by seeking many different mates
(Archer, 1996). Males who are successful in obtaining a mate will enhance their
reproductive success, resulting in these traits that contributed to the success as becoming
more common in the species (Browne, 1998). Males can exert control over their
attractiveness to females by regulating the amount of resources they have to offer to
mates (Hill & Reeve, 2004). When two males compete for one female the winning male
will always be the male who can continue to bid higher (offer more and more resources)
than the other male (Hill & Reeve, 2004). The amount of resources required will increase
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as the female’s quality increases and as the other male becomes more of a threat (Hill &
Reeve, 2004). It is predicted that the higher quality male, with greater resources, will
obtain the female (Hill & Reeve, 2004). When two females are bidding for one male, the
winning female is the individual who, “when she makes her minimum profitable bid,
would potentially yield higher offspring success for the male” (Hill & Reeve, 2004).
These findings all suggest that men and women have evolved different adaptations that
are used to guide their mating strategies (Eastwick & Finkel, 2008).
Mate Preferences Between Sexes
Mate preferences found in nature are very similar to those found among humans.
Men seek out women who possess prominent cues that reveal their biological fitness,
whereas women seek a single man who will be able to provide resources (Urbaniak &
Kilmann, 2006). Biological fitness can be seen as being youthful and physically
attractive, while a man who possesses resources is seen as being more likely to commit
(Urbaniak & Kilmann, 2006). Men have shown preferences for women with child-like,
neotenous facial features, because they promote reproductive success (Hopcroft, 2002).
These features advertise a female’s youth and viability to a male mate, which will
promote protective and supportive behaviours in males (Hopcroft, 2002). Females, being
the more cautious sex, place greater importance on mates who have higher social status,
ambition, and earning power that will all contribute to the increased fitness and survival
of her offspring (Hazan & Diamond, 2000). In terms of physical attractiveness, both
males and females look for these qualities. For females, this is a marker of good genes,
which will also increase the offspring’s fitness (Koehler et al., 2002). Physical
attractiveness consists of facial attractiveness and symmetry, height, body build,
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attire/grooming, body language, and cues that signify dominance (Urbaniak & Kilmann,
2006). Both females and males show preferences for symmetrical bodies and faces. This
demonstrates an adaptive mechanism of mate choice that signifies superior phenotypic
and genotypic qualities in mate preferences (Koehler et al., 2002). Men look for features
that are marks of reproductive potential, whereas women seek features that signify
genetic fitness, resources, and protection (Archer, 1996). Research done involving online
dating confirms these preferences. Men’s income predict the number of emails from
women, and the physical attractiveness of a user’s photo can predict the number of emails
a woman receives (Eastwick & Finkel, 2008). This standard evolutionary model of mate
preferences shows evolved guidelines that act as forces upon males and females to desire
certain qualities in a mate that will increase their own, and their offspring’s fitness
(Hazan & Diamond, 2000).
Short vs. Long-Term Mating Strategies
Short-term mating constitutes partners engaging in sexual activity when there is a
low probability of a relationship continuing (Wiederman & Dubois, 1998). Long-term
mating is when there is an increased likelihood of a long lasting relationship (Wiederman
& Dubois, 1998). In terms of short-term mating men have a higher interest in short-term
mates than women do, men prefer a greater number of sexual partners over time than
women, and men require less time to elapse before engaging in sexual activity than
women (Schmitt et al., 2001). This is due to differences in maximizing fitness. Sex
differences arise when comparing short-term and long-term mating. When considering
short-term mating men place more emphasis on physical attractiveness, and prefer mates
who are not looking for a long-term relationship (Wiederman & Dubois, 1998). In short-
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term mating, women value financial resources, generosity, and cues to genetic fitness
(Wiederman & Dubois, 1998). Women also prefer short-term mates who are seeking
long-term relationships, allowing for the possibility of a future (Wiederman & Dubois,
1998). In long-term mating, men have higher standards for physical attractiveness in a
long-term, female mate (Wiederman & Dubois, 1998). In long-term mating for women,
the emphasis of importance on available resources becomes more significant of a factor
(Eastwick & Finkel, 2008).
Benefits of Promiscuity (Short-Term Mating) In Human Mating
So-called promiscuous males benefit evolutionary by increasing their
reproductive fitness (Schmitt et al. 2001). There are many explanations as to why
promiscuity in females is beneficial. Engaging in short-term mating is advantageous
because women can gain immediate material resources (Wiederman & Dubois, 1998).
Women may seek superior short-term mates as a back up to their current mates (Schmitt
et al., 2001). In areas where the number of viable long-term partners is low, short-term
mating is functional for women (Schmitt et al., 2001). Many women find a short-term
mating encounter to be just as positive as a man would (Campbell, 2008). As well, shortterm mating could act as a “test run” for a potential long-term mate (Campbell, 2008).
The sex differences found in human mating strategies and preferences are
effectively explained by the standard evolutionary sexual selection theory, and account
for benefits to reproductive fitness. These explanations relate closely to the theories
underlying sexual selection in the animal kingdom.
Impact of Sexual Selection Evolutionary Theory on Gender Roles
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Original Bias in Darwin’s Theory
Darwin’s original evolutionary theories fit well with the social beliefs of the 19th
century. The animals he described in his theories were, “cast into roles from a Victorian
script” (Hubbard, 1979). His account of human nature presented the active male and the
passive female (Hubbard, 1979). This pattern of male dominance and female resistance
(or discriminating nature) has led to the development of patriarchal arrangements in
human society (Vandermassen, 2004). This evolution of patriarchy has arisen due to the
conflict between reproductive interests (Archer, 1996). Men have gained the advantage
over women due to size and strength, but also by overcoming female choice (Archer,
1996). The theory of sexual selection, despite its supporting evidence, has allowed for the
evolution of male exploitation of the reproductive efforts of females (Vandermassen,
2004). In presenting the female as “coy” and “passive”, the female’s involvement is not
value neutral (Vandermassen, 2004). Darwin’s original presentation of theories often
seems to be suggesting that a male’s secondary sex characteristics are more important
than a female’s (Vandermassen, 2004). Today, due to increased female involvement in
the field of animal behaviour and evolution, the facts are presented more logically and
more inclusive.
Due to the societal climate during the original publication of these theories, some
gender biases can be found in the literature. However, especially in today’s society, these
gender biases are not taught or the emphasis of the arguments.
Division of Labour
Boys are taught to be aggressive, tough, willing to fight, and to be self-reliant. In
contrast girls are taught to be industrious, responsible, and obedient (Archer, 1996).
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These tendencies in boys are not only enforced by society but are shown to be a general
tendency in mammalian species. This difference in enforced traits can have significant
implications at the workplace (Browne, 1998). Status in society was shown to have
reproductive payoffs for men (Browne, 1998). This has left men to be more interested in
reaching high status in a hierarchy than women and more likely to utilize aggressive
behaviour to reach the top of this hierarchy (Browne, 1998). To reach the top of a
workplace hierarchy one must display competitiveness, willingness to take risks, and
room for making a large investment (Browne, 1998). Men, being less invested in child
rearing and more determined to gain status and resources, disproportionately occupy
these high status positions in occupational hierarchies (Browne, 1998). As well, in
patriarchal systems men are provided the power and status to achieve the benefits of this
division of labour (Eastwick et al., 2006). Young women have low task related selfesteem when they compare themselves to men. This may have evolved because such a
trait advertised youth and controllability, both attractive characteristics to a male mate
(Hopcroft, 2002). This tendency of women belittling their contributions and capabilities
may help to explain the stereotype of women as weak and inferior, and men as strong and
superior (Hopcroft, 2002). These tendencies may result in women not pursuing additional
training and education in order to develop their abilities and skills (Hopcroft, 2002). This
will then act to exclude women from the benefits of this division of labour (Hopcroft,
2002).
Benevolent and Hostile Sexism
Paternalistic attitudes (restriction of freedom, protecting and cherishing women
etc) have evolutionary been considered an attractive quality in a mate (Hopcroft, 2002). If
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women enforce these attitudes they will be met with benevolent discrimination. This is
the idealizing and rewarding of women who remain in their conventional, stereotyped
roles (Eastwick et al., 2006). In contrast, hostile sexism is when women who take on
traditional male roles (aggressiveness) are demeaned or punished (Eastwick et al., 2006).
This traditional, idealized view of women that causes both benevolent and hostile sexism
is founded by evolutionary sex differences.
Sexual Double Standards
Young girls are taught to be sexually restrained (Archer, 1996). Unsurprisingly,
women with more elaborate sexual histories are met with derogatory evaluations
(Jonason et al., 2009). However, men with many sexual partners are viewed as having
more prestige than those who do not (Jonason et al., 2009). Herein lies society’s sexual
double standard. According to sexual selection theory men should be more approving of
casual sex and should have larger numbers of mates in order to increase reproductive
fitness (Oliver & Hyde, 1993). Sexual success among males is based on access to a
limited resource: women’s sexuality (Jonason et al., 2009). These views have lead to the
existence of the double standard of society’s easygoing attitudes towards male
promiscuity and conversely intolerant opinions of female promiscuity.
Alternative Explanations
Alternative perspectives other than evolutionary sexual selection can explain the
mating strategies and preferences stated throughout the literature. By including these
alternatives explanations one gains a more thorough perspective on human mating.
Attachment theories state that both males and females seek qualities that make a good
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attachment figure (kindness, warmth, and competence) (Hazan & Diamond, 2000).
Unlike sexual strategies theories, these qualities do not vary as a function of sex (Hazan
& Diamond, 2000). According to social role theory, an individual can adopt sex
differences in social behaviour through the learning of sex typed skills and beliefs, and
through gender role expectancies (Archer, 1996). Cultural traditions can enforce
aggressiveness and dominance as well (Archer, 1996). It is also a possibility that sex
differences in sexual behaviour are due to the individuals reporting these differences
rather than actual behavioural differences (Fisher, 2009). These biological differences
may exist but it is possible that they are exaggerated due to the impact of societal and
cultural beliefs (Fisher, 2009). Participants of these studies that are providing evidence
for sexual strategy theories may state specific preferences and strategies as more
favourable due to the preexisting assumptions of what society would expect of them
(Eastwick & Finkel, 2008). As well, the focus of these arguments is that sexual activity is
based on reproduction and creation. There is the alternative explanation involving
romance, love, and realistic, loyal commitment (Vine, 2000). Finally, there is the classic
psychological perspective that states individuals seek a long-term partner who is similar
to himself or herself in looks to avoid being rejected or dissatisfied (Schneider et al.,
2005).
These arguments present findings parallel with those found throughout the
evolutionary literature, however their modes of inquiry and exploration are different. This
allows for a holistic view of human mating strategies.
Conclusion
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It is clear that there are sex and gender differences within the theory of sexual
selection. Evolutionary perspective maintains that there are differences in selective
forces, mating strategies, and mate preferences found between the male and female sex.
These differences are what allow for specific adaptations and strategies that are meant to
optimize an individual’s mating and reproductive success. Evolutionary speaking, this is
the main goal of human mating: reproduction and maximized fitness. Just like the rest of
the natural world, humans are not excused from the laws of evolution. To deny these
differences does not strengthen any argument due to the fact that there is mounting
evidence to support the theories. Unfortunately, it is also clear that these theories that
emphasize sex differences in order to explain sexual selection have severe implications
for society, gender roles, and sexual discrimination. The facts and explanations
supporting these evolutionary theories are not directly troublesome. It is during the
process of interpretation where the emphasis and focus of the science becomes lost in
translation. This problem of negative interpretation is what causes significant
implications on gender roles. Despite these negative consequences of evolutionary
theory, it appears that as society evolves, radical changes are being made to combat these
expected roles and to enforce new ways of thinking. In order to better understand human
nature, behaviour, and its mechanisms all possible perspective must be taken into
account. It is only then that society can evolve, embrace differences between the sexes,
and enhance current theories.
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