Any method that prevents the conception of offspring in sexually active women.
Birth control became popular in the 1960s when it was introduced to the public as a means of preventing unwanted pregnancy, which has played a major role in the movement of sexual liberation for women (Cobey et al. 2011). Birth control is unique to humans because it grants women the decision to choose who they want to conceive offspring with while giving them the liberty to engage in copulation with those they do not want to bare children with. Of course, sexual intercourse without the implication of pregnancy only works if the method of birth control is used correctly. Hormonal contraceptives work by mimicking pregnancy in the female body through the implementation of synthetic hormones like estrogen and progestin, disrupting the natural hormonal cycle. It does this by preventing ovarian hormone production. Also, since such a method is evolutionarily unnatural, there are several physiological, psychological, and behavioral implications for taking birth control. Additionally, recent studies on birth control have revealed partially concealed ovulation across humans, since it has been shown that naturally ovulating women emit more signals to the opposite sex during peak ovulation with men detecting such signals for successful mating as compared to unnaturally cycling women.
The Evolutionary Roots of Birth Control
In present day, there are several different types of hormonal contraceptives on the market ranging from oral contraceptives (i.e., birth control pills) to the use of a patch that absorbs hormones through the skin and into the bloodstream. Oral contraceptives are the most popular form of birth control, making up 82% of all birth control users (Welling et al. 2012). Other methods of hormonal birth control with varying effectiveness include vaginal rings, injectables, and implants. Methods of birth control that do not emit hormones in order to interfere with the natural ovulatory cycle include IUDs (i.e., intrauterine devices that are inserted in the uterus and into the fallopian tubes, blocking the sperm from fertilizing eggs located in the ovaries of women), condoms (both female and male), and sterilization. Lastly, women can track their ovulatory cycles to predict whether or not they are experiencing peak ovulation and only choose to have sexual intercourse on the days they are least likely to get pregnant. Of course, this type of birth control is the least effective when it comes to both contracting sexually transmitted infections (STIs) and preventing pregnancy. That is, the human body is designed to get pregnant, and each body has its own unique biology, so it’s better to be safe and use other methods of birth control alongside the natural method.
As aforementioned, women are more likely to conceive a child during peak ovulation. According to the typical female ovulatory cycle, there are 5 to 6 days during a complete cycle when women can conceive (Carmen et al. 2013). The ovulatory cycle lasts about 28 days with the conception period occurring at the beginning of each cycle. There are three total phases in the ovulatory cycle: menses, follicular, and luteal. During the luteal phase, the risk of pregnancy is at its lowest, and progesterone levels are at its highest point. Ovulation occurs during the menses cycle and for only 1 day out of the 28-day cycle. On this day, the vagina produces a substance chemistry that allows sperm to survive in the female reproductive system. That is, during this time period, the sperm is capable of fertilizing an ova over the course of about 5 days, as long as it is encapsulated in the right fluid chemistry at room temperature. On the days where the window of peak ovulation is not open, the female vagina actually produces a fluid chemistry that has a spermicidal effect, making it much harder to conceive a child on those days. Such a complex cycle explains why humans did not conceive an insurmountable amount of offspring during ancestral times and why the use of natural birth control (i.e., having intercourse in accordance to one’s ovulatory cycle in order to increase or decrease the likelihood of pregnancy) is more effective (75–98%) than many might think. On top of that, women were usually pregnant or breastfeeding during ancestral times, which prevented them from ovulating frequently.
During peak ovulation, it has been observed that women behave differently as compared to times when they are not ovulating, assumedly to attract more desirable mates for reproductive success (Carmen et al. 2013). According to Gangestad and Thornhill’s (1998) ovulatory-shift hypothesis, women are more likely to engage in behaviors to attract mates during periods of high fertility. Such behaviors include sexual opportunism (i.e., making sexual advances when available) and more positive attitudes, sexual interest, infidelity, and willingness to engage in sexual activity with unfamiliar men (Geher 2014).
These behavioral changes during the ovulatory cycle are related to mating intelligence (MI). Mating intelligence is considered to be the reproductive system of the mind. In other words, MI is the degree of cognitive ability to successfully engage in proper mating strategies that will increase the chance of choosing the most fit partner to assure the reproduction of vital offspring. Cognitive abilities that comprise of MI include mate choice, acquiring the targeted mate, mate retention, and mate decisions regarding the dissolution of courtship. Additionally, predictors of high MI consist of greater and more frequent acts of both giving and receiving oral sex (i.e., indicators of courtship and determining mating value) and reproductive success (RS). Sensibly, it has been observed that MI significantly increases during peak fertility as preferences to access “good genes” increase. Because birth control interferes with the natural ovulatory cycle, the absence of peak ovulation in women on hormonal contraceptives makes it less likely for them to experience a spike in MI during times when they would usually be ovulating (Carmen et al. 2013).
As mentioned, hormonal birth control works by mimicking pregnancy in the female body through the implementation of synthetic hormones like estrogen and progestin, disrupting the natural hormonal cycle. Because the female body believes it is pregnant, it cannot go through its natural process of fluctuating hormones suitable for reproductive success. In other words, the female body already thinks it succeeded in conceiving a child, so it does not need to go through the process of ovulation for the duration of the pseudopregnancy or the length of time the female is using birth control.
During a natural ovulatory cycle, estradiol levels are highest at peak ovulation. These high levels of estradiol are believed to be the cause of behavioral changes observed across women, elevating mating intelligence. Additionally, men are more receptive to such behavioral signals indicating a rise of MI. For example, a study performed on female strippers reported that men are far more likely to tip female strippers when they are ovulating as compared to female strippers who are not ovulating or who are on birth control. Such estradiol-linked MI behaviors that could account for this phenomenon include elevated female initiations for sex, a greater masculine preference, more risk-taking behaviors, an elevated tendency to wear skimpy clothing, higher instances of erotic movement and dancing, and more symmetrical body parts (Geher 2014). In addition to bigger tips, males reported feeling more attracted to the voices and scents of ovulating women. Men also found photos of ovulating women to be more attractive. In accordance, these findings are linked to a concept known as concealed ovulation.
Concealed ovulation is when female organisms and their suitors are unaware of when females are ovulating. Due to findings that support a change in female behaviors and male receptiveness during female peak ovulation, it turns out humans experience a more low-key form of overt ovulation. That is, if female humans really had concealed ovulation, their mating patterns would stay the same regardless of whether or not they were ovulating or on birth control. Because of this, it is more suitable to say that human females experience partially concealed ovulation, since most of their elevated mating behaviors during peak ovulation are somewhat below awareness or the threshold of consciousness.
Since hormonal birth control is not a natural mechanism in the human species, it understandably does not go without its physiological, psychological, and behavioral implications or side effects. In a sense, birth control goes directly against the environment of evolutionary adaptiveness (EEA). According to the evolutionary theory, all organisms are meant to survive and pass on their genes through reproductive success. Birth control halts that natural process. That is, with the freedom for women to control their own fertility, there are inevitable consequences.
On a physiological level, birth control has been shown to elevate the risk of myocardial infarction (heart attack), ischemic stroke, and blood clots. On the other hand, birth control has also been shown to decrease the prevalence of ovarian and endometrial cancer (Welling et al. 2012). Psychologically, birth control has been reported to elevate intense affective responses toward infidelity and sexual jealousy, which is thought to be a consequence of synthetic estradiol in birth control, but not due to synthetic progestin (i.e., another substance that is usually in birth control). Other psychological effects include higher rates of depression and a decreased interest in sex.
Juxtaposed with the increased MI behaviors experienced by naturally cycling women during peak ovulation, women on birth control experience a whole host of different “synthetic-hormone-induced” reactionary behaviors. Such reported behaviors include greater mate retention tactics (e.g., emotional manipulation, physical violence, intrasexual competition) from increased levels of emotional jealousy, greater engagement in short-term mating as compared to long-term mating throughout the entire ovulatory cycle, more sexual partners, and reduced sexual functioning (Welling et al. 2012). Overall, the absence of natural hormones throws typical mating strategies out of whack and decreases cyclical and perhaps more beneficial mating intelligence tactics across women. The trade-off, of course, is preventing pregnancy, which is a result of our Western cultural landscape at a time where personal success has the tendency to trump building a family at a young age.
Aside from the negative implications of birth control, there are objective differences between women who use birth control as compared to women who do not. One difference is affect variability. Naturally cycling women experience greater affect variability during their cycle than women on birth control. That is, many women experience greater mood stability while taking birth control because there are no longer mood swings associated with the varying influx of hormones during the natural ovulatory cycle. In addition, this stabilizing effect is especially true for women who experience intense premenstrual emotional symptoms associated with low progesterone to estrogen ratios (Oinonen and Mazmanian 2002). The greatest difference in affect variability occurs during menstruation (i.e., withdrawal bleeding) when naturally cycling women have a tendency to experience elevated negative mood states as compared to unnaturally cycling women.
Interestingly, Natale and Albertazzi’s (2006) study on mood swings across the menstrual cycle found that there were only significant mood differences between naturally cycling women and those who were on birth control when the women who were on birth control had premenstrual syndrome. Despite this, the ovulatory cycle (natural or unnatural) generally does impact mood and mood patterns across all women, especially when it comes to depression-dejection symptoms. For all women, it is typical for mood to worsen before menstruation and for mood to lighten post-menstruation. Overall, birth control pills help to better stabilize mood in women suffering from premenstrual syndrome, but do not significantly (albeit slightly) stabilize or improve mood across healthy individuals. These findings suggest that more research needs to be done in order to determine how much birth control really does affect cyclical mood states during the ovulatory cycle but suggests differences do exist, especially for those who suffer premenstrual symptoms out of the range of normalcy. The takeaway here is that the differences are more subtle than one might think.
Another studied change in behavior between naturally and unnaturally cycling women is sexual interest and response (Graham et al. 2007). Birth control decreases the level of testosterone in a woman’s body, which is responsible for a healthy libido. Because of this, it has been reported that women who have been on birth control for at least 3 months show a decrease in sexual interest and response. Also, according to Graham et al. (2007), there is a relationship between decreased libido and a lower frequency of sexual thoughts across birth control participants. However, despite these findings, many birth control participants did not experience a lowered sex drive or lowered sexual satisfaction with their partner. Such findings suggest, again, that more research needs to be done on how much the testosterone-lowering effects of birth control actually change sexual behavior. Because birth control is used so prominently across Western cultures, such apparently negligible differences don’t appear to be enough for women to stop using contraceptive birth control.
One more difference between birth control users and nonusers is the aforementioned difference in affective jealousy. Women who are on birth control have reported experiencing higher overall levels of jealousy as compared to non-birth control users. Such a finding suggests that state jealousy must be hormone sensitive, and it has been deduced that estrogen levels are the culprit (Cobey et al. 2012). In other words, naturally cycling women experience more jealousy in their most fertile state, when estrogen levels are high, while women on birth control experience a more steady yet consistently higher level of state jealousy throughout the entire cycle as compared to naturally cycling women in their non-fertile state. In addition, women, taking oral contraceptives who are paired, experience more jealousy than women taking oral contraceptives who are single. Overall, such an interesting finding posits that birth control alters mating intelligence and thus mating strategies in bizarre ways and perhaps plays a role in negatively impacting romantic partnerships.
An additional study conducted by Cobey et al. (2011) supported his previous findings on the relationship between estradiol levels and self-reported jealousy across women, by showing that elevated levels of ethinyl estradiol affect all types of operationalized jealousy. These jealousy types include reactive, possessive, and anxious jealousy. On top of that, the results remained significant even after controlling for relationships status, age, and mood. Lastly, this study found that there is no correlation between self-reported jealousy and progestin dosages, which further supports that estrogen and its synthetic counterparts are the jealousy-inducing culprits.
In the previous discussion, we have viewed birth control through the lens of hormonal contraceptives. Since birth control can be conceptualized as any method that prevents the conception of offspring in sexually active women, it’s interesting to note how birth control might have been implemented in the ancestral landscape, before the rise of medicine. A fascinating theory to examine is the reproductive suppression hypothesis for explaining eating disorders (Wasser and Barash 1983). The reproductive suppression hypothesis posits that females suppress their reproduction when the current conditions are not in favor of reproductive success or offspring survival. That is, the female believes that the benefits of suppressing reproduction (i.e., depleting fat stores to the extent of stopping the ovulatory cycle, amenorrhea) outweigh the costs and that resources will be more plentiful and readily available in the future to assure reproductive success. This reproductive suppression is done through extreme dietary behaviors, and preferring a thinner body ideal can be a way to manipulate the timing of reproduction.
In addition, a variant of this hypothesis was proposed by Surbey (1987). Surbey theorized that females can become anorexic as a way to stunt development. If a female is predisposed to mature earlier in a modern-day society that favors late maturers, anorexia is a way to change a female’s natural developmental trajectory to one of a late maturer. Again, this is done by reducing fat through strict dietary behaviors. The benefit of late maturers in modern society is that it takes reproduction (i.e., reduces libido, attracts fewer males, induces amenorrhea) out of the equation when academic and professional success is more valued in the female’s family. Overall, anorexia nervosa may explain an extreme method of birth control in ancestral times that has span of control in the modern landscape.
Birth control is a means of preventing unwanted pregnancy and is unique across modern human females. Birth control within itself goes against EEA causing a whole host of negative implications while defying the main objective for all living organisms to survive and successfully reproduce. Overall, much more research needs to be done on both the negative and positive implications of birth control.
- Cobey, K. D., Buunk, A. P. B., Roberts, S. C., Klipping, C., Appels, N., Zimmerman, Y., Coelingh Bennink, H. J. T., & Pollet, T. V. (2012). Reported jealously differs as a function of menstrual cycle stage and contraceptive pill use: A within-subjects investigation. Evolution and Human Behavior, 33, 395–401.CrossRefGoogle Scholar
- Gangestad, S.W., & Thornhill, R. (1998). Menstrual cycle variation in women’s preference for the scent of symmetrical men. Proceedings of the Royal Society of London B, 262, 727–733.Google Scholar
- Geher, G. (2014). Evolutionary psychology 101. New York: Springer.Google Scholar