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Derivation of Offensive Selection From Natural Selection as It Relates to Sexual Strategies

Laura R. Thatcher
Rochester Institute of Technology

This analysis presents an alternative idea to that of sexual selection which is called offensive selection, coupled with defensive selection. These categories of natural selection, predominately offensive selection, pave the way for an evaluation of the sexual strategies that have evolved among human males and females in selecting a mating partner. Some of these discussed characteristics are physical attractiveness, commitment, financial status, and health. Preferences for these characteristics vary among males and females and also among short-term versus long-term relationships. They have become an evolved predictor for fertility and survivability of offspring. These predictors are a product of offensive selection in evolutionary history of the human species.

Charles Darwin proposed natural selection as the process by which adaptations are created and change in a species takes place over time. This results in gradual changes caused by successful variants (changes) increasing in frequency due to their contribution to survivability of the species. Darwin was perplexed by the fact that some species displayed characteristics that would seem to cause more predation instead of less. He realized that these characteristics were beneficial to mating instead of warding off predators. These attributes are ones, which could harm the organism's chance of survival but increase their chance of reproduction. He called this process sexual selection (Buss, 2002). Sexual selection is similar to natural selection in that it also aids in the increased survivability of a species. Natural selection refers to the selection that aids in the survivability of a species in general, while sexual selection is more specific and merely relates to a particular way in which selection aids in the survivability of a species. Sexual selection is therefore not a separate entity from natural selection because natural selection encompasses sexual selection, making it a sub-category of natural selection.

It would be more appropriate to break natural selection down into two categories, one which sexual selection would fall under. These two categories will be called defensive selection and offensive selection.

Defensive and Offensive Selection

Defensive selection refers to the survival of traits that prevent competition or predation within a species. It is primarily responsible for the survival of the individual and secondly responsible for the survival of the species through the survival of each individual member. Defensive selection deals with traits, which survive the test of time due to their ability to help an individual organism survive long enough to reproduce. Offensive selection is unconcerned with the survival of the individual and the prevention of predation. Offensive selection may in fact cause predation to be worse. The primary goal is to ensure survival of offspring and secondly to ensure survival of the species through survival of each offspring. Offensive selection deals with traits, which help an organism find a suitable and healthy mate to reproduce with. It is responsible for traits that display fertility and attractiveness to the opposite sex.

Both selection mechanisms work to ensure that the species survives and flourishes but defensive selection does it thorough ensuring survival of the individual already present while offensive selection does it through the survival of the offspring based on fertility and health of the individual. Defensive selection serves to prevent death of existing organisms, while offensive selection serves to enable new life for future organisms. Defensive selection is necessary for offensive selection to occur, but offensive selection will always prevail in expressing the trait. If the expression of a certain trait simultaneously aids in the acquisition of a mate and the production of offspring as well as susceptibility to predators, the trait will be expressed despite the detrimental affects it could potentially fabricate.

These terms are designated as such because defensive selection defends the species through individual defense mechanisms against predators and offensive selection actively and offensively aids in producing new offspring to benefit the species. Let us take for example, a soccer game. This soccer game will be called Natural Selection. The two competing teams will represent two species interacting in the same environment. The defensive players stay back closer to the goal that belongs to their team. They are defending the goal from having points scored against them, which could cause them to lose. The act of a team (or species) scoring a point is analogous with the death of an individual organism of the opposing team and if that team loses the game then it represents the death of that species. The offensive players of one team actively move forward through the players of the other team in order to score points. The act of a team (or species) scoring a point is analogous with the birth of a new organism in that species. The offensive players are actively trying to gain more points, or more organisms, while the defensive players are trying to protect the team against losing points to the other team, or in this scenario, losing organisms to death. Both types of players are necessary for the game, just as both types of selection are necessary for the survival of a species in the game of life, otherwise known as natural selection.

Intrasexual Competition and Intersexual Selection

Offensive selection is the basis for evolution of sexual strategies through intrasexual competition and intersexual selection, which are both specific ways to express sexual cues toward the opposite sex. Intrasexual competition is competition between members of the same sex for mating access to members of the opposite sex. Intersexual selection is preferential choice exerted by members of one sex for members of the opposite sex (Buss, 1988). Both of these strategies encompass different features such as health, attractiveness and behavior. The difference lies in whether the organism is dealing with its own sex or the opposite sex. Intrasexual competition and intersexual selection are both an integral part of offensive selection. They both ensure fertility of mates and survivability of offspring, but do not aid in the immediate survival of the individual. Among humans, males and females both display characteristics of intrasexual competition and intersexual selection. The devices that are used for each type of selection vary among men and women and among different types of situations. In our evolutionary history, both men and women have pursued short-term and long-term mating and mating strategies under conditions where the reproductive benefits have outweighed any costs (Schmitt & Buss, 1993).

Long-Term Versus Short-Term Mating Strategies

The effectiveness of an act of attraction depends on three variables: the mate preference of the desired partner, whether there are rivals trying to attract the potential partner, and the type of relationship sought with the partner. Men and Women both seek long-term and short-term relationships, but preferences for both men and women shift methodically depending on whether a short-term or long-term relationship is desired (Schmitt & Buss, 1996). Tactics used for finding a potential mate differ based on the type of relationship being pursued and the gender involved. It has been shown that tactics relating to physical attractiveness will be more effective in the context of short-term than in the context of long-term relationships (Schmitt & Buss, 1996). Physical attractiveness is an attribute that is less important in long-term relationships.

Women who tend to seek short-term relationships seem to prefer men higher in status and dominance (Schmitt & Buss, 1996). Women are more interested in social status and position than emotional aspects of men for a short-term relationship. This can be credited to the fact that a socially attractive guy is ideal to the female seeking him out because he is directly beneficial to her, increasing her status and appearance to others, whereas an emotionally attractive male is ideal for a long-term relationship and the care provided to her and her children. As a whole, men devote a larger portion of their total mating effort to short-term mating than do women (Schmitt & Buss, 1993). The innate goal of a man is to increase his chances at having healthy offspring. He accomplishes this by having sex with numerous women. The more women he has sex with, the greater the chance he will produce healthy offspring. Feminist Theory suggests that women would be likely to report, and probably experience, a desire for fewer sexual partners (Silverstein, 1996). This supports the idea that, in nature, females are expected to evolve traits that maximize offspring quality rather than quantity (Bailey, Gaulin, Agyei & Gladue, 1994). From an evolutionary perspective, seeking and acquiring one committed male is more beneficial to the success of our species than seeking and acquiring many non-committed males. Women participate in short-term relationships to increase their status, attractiveness and desire as seen by other men. This enables them to display characteristics and roles necessary to reel in males for a long-term relationship. Men can also utilize short-term relationships as a means for making themselves appear to be more desirable and relationship worthy. Both men and women always seem to be more desirable when someone of the opposite sex is already pursuing them. Engaging in short-term relationships allows people from both gender categories to display and search for qualities they want in a potential long-term mating partner. Women, especially, use short-term mating for self-promotion and competitor derogation, which increases men's perceptions of their sexual availability (Schmitt & Buss, 1996). This mating strategy is a type of intrasexual competition and is practiced by both men and women. This competition is most widely used for engaging in short-term relationships.

When pursuing a long-term relationship and sexual strategy, both sexes cope with the difficulties of finding a partner who will commit to the relationship for a sustained period of time (Schmitt & Buss, 1996). The top ranked qualities men and women look for in each other are identical and consist of kindness, understanding, and intelligence (Hazan & Diamond, 2000). Men and women both prefer understanding and kindness more in potential long-term mating partners than in potential short-term mating partners (Schmitt & Buss, 1996). These personality characteristics, along with displaying signs of commitment and expressed expectation of a long relationship are more effective at attracting long-term mates than short-term mates (Schmitt & Buss, 1996). Long-term relationships are most ideal for raising offspring and these aforementioned personality characteristics create an ideal environment for ensuring the health, safety and well being of the offspring.

The characteristics of love, affection, kindness, commitment, understanding and so forth are all in existence because as a species we thrive in groups, working together (Ruse, 1993). The human species would not have the success and superiority that it does today if not for the evolution of the need to belong. It is possible that nature masks the underlying and fundamental reasons for mating in the characteristics that people look for in a possible mate (Ruse, 1993). People say they enter a relationship because they love each other when in fact having that relationship which combines desirable and successful genes is what is most beneficial for the survival of our species. These traits, along with the following ones discussed are all products of offensive selection and aid in the survival of offspring through sexual strategies and reproductive cues.

Physical Characteristics

Female reproductive capacity is closely linked to bodily features, such as facial characteristics and waist-to-hip ratio that denote youth, health and fertility. A woman's reproductive age is limited; therefore, youth is highly valued in females for mate preferences (Archer & Mehdikhani, 2003). Contrary to females, males can reproduce throughout life, which has caused the evolution of youth to be of less importance when compared to its value in females. Women show greater intrasexual competition for displaying cues that correlate with reproductive value and fertility through enhancing physical attractiveness, appearing healthy, youthful and hard-to-get (Buss, 1988). Females tend to be more selective than males when choosing a mate, which causes males to participate in intrasexual competition by competing for females (Schmitt & Buss, 1993). They do this through enhancing their size, stature and dominance in society. Males and females both engage in intrasexual competition through enhancing their physical attributes. Females enhance attributes that show higher fertility while males enhance attributes that show higher status and dominance.

Beauty and bodily form have evolved in animals to be perceived as cues to high parasite resistance in choosing mates. Similarly, humans are affected by beauty and form in the opposite sex. One of the ways in which beauty and form is looked at is through bodily symmetry and in particular, facial symmetry (Grammer & Thornhill, 1994). Offensive selection favors those traits that advertise resistance to parasites and general weakness in organisms. In humans, symmetry is linked to fitness and sexual attractiveness. Symmetry appears to be more important in short-term strategies than in long-term strategies (Archer & Mehdikhani, 2003). Females tend to prefer averageness and symmetry for short-term relationships (Grammer & Thornhill, 1994), but tend to prefer less attractive and less symmetrical men for long-term relationships (Archer & Mehdikhani, 2003). This may be attributed to the fact that more attractive and symmetrical men tend to pursue attractive and symmetrical women for short-term relationships and subsequently make themselves unavailable for long-term relationships.

Parental Investment and Paternal Uncertainty

One of the central driving forces behind offensive selection is the degree of parental investment each sex devotes to their offspring. Parental investment is defined as any investment by the parent in an individual offspring that increases the offspring's chances of surviving at the cost of the parent's ability to invest in other offspring (Schmitt & Buss, 1993). Parents have a limited amount of resources, including time and money, which can be allocated towards there offspring. This limitation puts restrictions on the number of offspring a parent can have and still adequately provide for them. It is also not a necessity that the offspring in question are the parent's own offspring. Theoretically, the sex that invests more in the offspring should be more choosy or discriminating about who they mate with, or intersexual attraction. Adversely, the sex that invests less should be more competitive for access to the valuable, but limited, high-investing members of the opposite sex (Schmitt & Buss, 1993).

In nature, the ratio of men to women is 1:1, one man for every woman. It would seem like neither sex would be challenged for mates, but this is not the case. The immediate reproductive benefits of acquiring sexual access to a variety of mates would have been much higher for men than for women throughout evolutionary history (Buss, 1995). Males reproduce more rapidly than females and females tend to invest more time into offspring; therefore, they are less available and in short supply (Bailey et al., 1994). This difference in reproductive rate hinders the availability of females to males, which causes females to be more selective, choosing from a large number of males, and males to be more competitive, competing for a short supply of females (Schmitt & Buss, 1993). Females are better at maximizing fitness by being more discriminating in order to obtain a male with good genes, resources, and parenting skills, but males are better at maximizing fitness by seeking to mate with many females (Archer, 1996). There is also an imbalance in the time of investment that is absolutely necessary for each parent to contribute. Females must at least contribute nine months of their time while males are only required to contribute a few minutes. This imbalance early on causes a general imbalance between the sexes in parental investment for the development of the offspring (Archer & Mehdikhani, 2003). Some men are better suited to the parental strategy rather than sexual strategy and this difference causes men to either be committed to a single partner with parenting skills or seek to fertilize many women with no parenting skills (Archer & Mehdikhani, 2003). Men better suited for the parental strategy are likely to be involved in long-term relationships, while men better suited for the sexual strategy are likely to be involved in short-term relationships. Men can be either low parental investors or high parental investors, but in general, women are always high parental investors. The mammalian method of reproduction and length of gestation are the major reason for their high investment in offspring (Archer & Mehdikhani, 2003).

Parental uncertainty is an innate psychological issue that men mainly have to deal with. A man can never be sure that the child he is providing for is really his, but he does not consciously realize this. Subconsciously, he can never be 100% certain. Women, on the other hand, can be 100% certain that their children are really theirs because they give birth to them. If a man is willing to contribute high parental investment than they are more likely to invest in offspring that are not biologically related to them if necessary (Wood & Eagly, 2002). Women tend to seek males that have the resources to support them and their offspring but males can be hesitant of such commitment because of this paternal uncertainty. The high parental investment women must invest in their offspring and the little minimum investment of men causes women to be particularly susceptible to being abandoned and left to raise children alone (Schmitt & Buss, 1996).

Offensive Selection of Emotional and Physical Characteristics

If there were no emotional attachment to mating, then men would have no incentive not to abandon their mate and offspring. The emotional relationship two people establish serves to create a need and dependence, which causes them to stay together for long periods of time and give maximum investment to their offspring. The attachment aspect of mating actually has the function of keeping people together because humans, as a species, thrive through commitment and community. People need each other in order to gain maximum benefit for themselves and for the species as a whole.

Every physical and emotional characteristic that aids in finding a favorable mate that will ensure offspring survival is a product of offensive selection. Every characteristic is one that brings people together, whether it is based on physical attractiveness or personality. This need for attachment and need to belong are basic needs, which not only ensure the survival of individual offspring, but also ensure the survival of our species. Humans need each other in order to survive and thrive as a species.

Competition, duration of mating, and physical characteristics, including facial symmetry, are all important aspects of human mating. These attributes aid in the production and survival of offspring, but do not increase survival of the parents. These sexual strategies are all an integral part of offensive selection, which have evolved to ensure success and survival of human beings.

Peer Commentary

Offensive Selection: Natural Selection Can't Keep Up

Adam O. Goldstein
Rochester Institute of Technology

The author presented an original theory of offensive selection, but the derivation from natural selection was flawed. Offensive selection was defined as dealing with the traits that display fertility and attractiveness to the opposite sex. It was the author's opinion that the selection of these traits would aid in enabling the birth of offspring and the survival of the species. This theory would work for species that have limited cognitive abilities, but reasons why this may not apply to humans will be presented.

In evolutionary terms, natural selection occurs over many generations at the very least. This has many implications for the theory of offensive selection. People change what they consider attractive almost every generation. Currently, at least in the United States, thin is in. Celebrities, the media, and pop-culture as a whole influence what people find attractive. This has many implications. If we constantly change what we find attractive, evolution through sexual selection has little chance to keep up.

Promulgation of a species, specifically humans, may depend on sexual selection; however, much of human sexual selection should be considered cognitive. For the reasons stated above, what we find attractive changes over time. These changes are based on cognitive perceptions rather than biological needs. People find someone attractive because of what they perceive as attractive, not what they are biologically predisposed to find attractive. If this theory of offensive selection were true, how does one explain that attractiveness in females has been measured by lower and lower weight over the years; yet the average weight has been getting higher and higher?

Darwin intended his theory of sexual selection to encompass all species; however, it really does not apply in the same way to humans. The attractive plume of a male peacock makes him more attractive to female peacocks and more visible to his predators; this is what Darwin had in mind when he developed his theory. Humans' physical or emotional attractiveness does not make them a target for predation, although it may make them a more viable option for mating.

Overall, breaking sexual selection into offensive and defensive strategies is a good idea; however, research and special considerations need to be taken into account for applying the theory to humans, because they are capable of far more complex thought than other species. In addition, one must take into account money and material possessions in addition to physical/biological characteristics.

Peer Commentary

Two Father Theory of Offensive Selection

Thomas E. Pilkerton
Rochester Institute of Technology

In Thatcher's paper on offensive sexual selection, she made several points regarding the male investment in offspring, analogizing the selection process as a soccer game. She wrote that both defensive and offensive players are necessary. This made sense, but it seems that the defense could be rendered useless if the offspring is prolific enough. That is, if the species could reproduce rapidly enough to offset the death rate, then the species should be able to perpetuate its existence. This analogy would be akin to having just midfielders and only a goalie. There does not need to be a balance between offensive and defensive selection for a species to be successful.

Perhaps the problem here was not with the idea of defense and offense, but rather with the analogy. Once a species is established, it seems reasonable that if it could reproduce fast enough then the defense would become irrelevant. This situation is analogous to a soccer game with two balls, one for each team. So long as one team consistently outscores the other team, success is ensured. So although defensive selection may be necessary initially, its usefulness declines when offensive selection is honed. It seems that in such a successful species as humans, defensive selection would no longer be an issue. There are laws and ethical standards in place to prevent predation within the species.

The second issue is more a creative solution to the mating process. Thatcher mentioned that males in general are either skilled in sexual strategy or parenting strategy. This in turn causes a dilemma in the mating scene. Females want males who will take care of their offspring (parental males) but also want males who can adequately provide this offspring (sexual males). In an effort to minimize competition, males could instead cooperate. Those males who are most desirable for reproduction could father many children, while those best suited for parenting could accept responsibility for these children along with the mother. This is not too far-fetched considering what Thatcher cited: "If a man is willing to contribute high parental investment then he is more likely to invest in offspring that are not biologically related to him (my italics) if necessary." This seemed counter-intuitive, but if it is true, then this arrangement of procreator and caretaker should be none too hard to accept.

In this model of sexual selection, the woman can have the best of both worlds: an ideal biological father and an ideal adoptive father. Men also are rewarded by this process. When a male matures (assuming he does) and desires a parenting role, he can take said role without the hassles of a sexual relationship. In this manner the male can then have both roles or just serve as a caretaker for other men's offspring. Those men who are caretakers will eventually appeal emotionally to their partners and could then be given the opportunity to fulfill sexual desires.

This system allows men to "sow their oats" and still have a framework for supporting the offspring. It allows women to be emotionally and biologically satisfied. It is a win-win situation on all accounts. It even serves to alleviate social pressures related to infidelity and single mothers. The only hitch would be to get everyone to agree.

This system for selection fits the analogy listed earlier in that it partially eliminates intersexual competition, thereby reducing the need for defensive selection. It also ensures that reproduction be carried out in accord with the male's capabilities, because he is no longer socially attached to the female.

Peer Commentary

Defensive Adaptations: A History of Mate Preferences

Brian P. Smith
Rochester Institute of Technology

This paper presents an interesting explanation for human behavioral adaptations that serve no purpose with regard to safety or survival. The development of these behaviors is known as "offensive selection," as opposed to "defensive selection." These behaviors concern the ways in which human beings search for mates.

The author makes a good comparison of offensive and defensive adaptations. Her use of a soccer game to demonstrate the purposes of these behaviors was a creative touch. Some concrete examples would also aid in her attempt to clarify the differences. For example, though not a human adaptation, the male peacock's ostentatious tail feathers inhibit its survivability by making it more visible to predators, but female peacocks use them to determine which possible mates are the healthiest. Similar examples that relate more directly to humans--for example, effort spent competing for mates instead of procuring needs--would more clearly demonstrate the ways in which offensive adaptations can often hinder survival.

The summary of intersexual selection is very well done and points out many concrete examples of those behaviors. The author does a good job of both presenting the behavior and providing an evolutionary framework for its development. The author also does a good job of detailing what is considered most attractive to men and to women, both physically and socially. It would be interesting to see in what ways intersexual selection and attraction have changed with the rapid development of human society and technology over the past thousand or so years. Can plastic surgery somehow circumvent these selection mechanisms? The author mentions facial symmetry as being a key factor in mate preference for both males and females, but with the technology that we possess today, such things as facial symmetry are quite changeable. It is possible that at some point humans will need to evolve entirely beyond physical attraction for mate selection.

Parental investment is another area of human behavior that the author say is an offensive adaptation. Properly rearing a child requires a large investment of time and resources, and decreases the survivability of parents, given that they have to worry about the survival of their child in addition to their own. From a purely defensive standpoint, it would seem that spending time rearing a child is detrimental, but from an offensive standpoint it is perhaps the most important task a person has, given that it is the culmination of all the other offensive adaptations. It seems that for many people, not caring for their own child is unthinkable--which appears to be a clear indication that offensive adaptations, though not as immediately useful to oneself as defensive ones, are as deeply ingrained as anything else in which human evolution has resulted.

Overall, this paper presents a number of good ideas regarding methods of mate selection within an evolutionary context. The author does not present any theories of her own, but she has written a very informative and well-organized summary of current thoughts in the field.

Author Response

Insightful Misunderstandings

Laura R. Thatcher
Rochester Institute of technology

In his review of my paper, Goldstein states that what people find attractive is constantly changing, so it cannot be a product of offensive selection. He specifically mentions weight in females and how the ideal weight seems to be getting lower and lower. In my paper I presented attractiveness as a cue for fertility and male-female attraction, but I did not discuss weight. I talked about facial symmetry and briefly touched on the hip-to-waist ratio. I am well aware that what humans find attractive is always changing and that there are differences in what individuals find attractive. Attractiveness in general, however, is still a cue to parasite resistance and fertility. What traits we actually see as attractive is indeed subjective. Because the average weight is actually getting higher, low weight must not be a cue for offensive selection, because it is not surviving natural selection. Consequently, I did not claim that weight was a cue for attractiveness.

It is not so much that physical and emotional attractiveness do or do not cause predation; what is more important is the fact that they do not aid in the survival of the individual but in the reproduction and survival of the offspring. If humans were dumb enough to be eaten or killed by something else, then attractiveness might aid in that.

Goldstein discussed money and material possessions, which I considered but in general weeded out in order to leave more room for the traits I found most important and interesting. In addition to this, I did not find adequate research to support these characteristics.

Pilkerton reasons that if a species could reproduce fast enough, then defensive mechanisms would be useless and would cease to exist. I think, however, that no matter how successful a species is, its members will still have defensive mechanisms, because no species is completely perfect and ideal in survivability. Just because one "sexual male" may be more fertile does not mean that a male more suitable for parental skills is incapable of reproducing. I am unsure that males should cooperate in the manner Pilkerton suggested, because it would result in a higher divorce rate and a higher number of fatherless children. It is possible that our species does not have the most perfect and ideal mating strategy possible. If we did, natural selection would cease to exist.

Both Goldstein and Smith discussed how a male peacock's feathers attract mates as well as predators. The reason why I did not use this example is because it is very overused and tends to create the assumption that no other good examples exist. Smith presents some additional and interesting ideas to my paper, which were accepted and greatly appreciated. Each of the reviews was insightful and well appreciated.


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