Have you ever wondered why you get a period?
Most of us know that a period, or menstruation, is the result of the uterine lining shedding after no successful fertilization happened the month prior. But why does our body build up the uterine lining in the first place, when more times than not no pregnancy occurs? From a biological standpoint, it doesn’t make any logical sense that the body would willingly expel large amounts of precious nutrients (Jarrell, 2018). Even odder, this process is so uncommon that only a few live birth mammals experience it (Ng et al., 2020). So why do humans menstruate? Why did our bodies evolve to have periods?
While many different theories have been brought forth, the current prevalent one is that menstruation is a side effect of the process of “spontaneous decidualization” (Jarrell, 2018). Decidualization is defined as the “functional and morphological changes that occur within the endometrium to form the decidual lining into which the blastocyst implants” (Ng et al., 2020). Basically, it’s the process of the uterine lining preparing to help sustain pregnancy. Most animals only undergo this process “following fertilization and contact with the conceptus” (Jarrell, 2018). However, in the few species that menstruate, decidualization is not triggered by contact with an embryo, but by the hormone progesterone before conception happens (Jarrell, 2018). Hence, it is called “spontaneous” decidualization since it does not rely on an embryo being present to start the process. But what is the advantage of this spontaneity? The current theories are that it provides “early protection of the mother from excessive invasion of fetal tissues” and/or it “permit[s] embryo selection by the mother” (Jarrell, 2018). However, this advantageous preemptive build-up of the endometrium leads to menstruation when an embryo is not present. Therefore, menstruation has no evolutionary advantage by itself, but it is rather a side effect of a different advantageous process (Jarrell, 2018).
At this point, you may be wondering: why is this information important? I would like to discuss two major areas of interest I feel this information could positively impact. Firstly, a better understanding of the evolution behind menstruation could shed light on new ways of treating reproductive health issues for women. A common one of these issues is recurrent pregnancy loss and other pregnancy complications. Ng et al. (2020) suggest that “failure to adequately prepare (decidualize) the endometrium…leads to abnormal implantation/placentation and ultimately to adverse pregnancy outcome.” Using this knowledge, they propose that physicians should focus their treatment plans for these complications on the time before conception happens, rather than during the early stages of pregnancy. Another reproductive health issue women face is menstrual disorders. A study conducted on young female Saudi university students found that “ninety-one percent of the students were suffering from some kind of menstrual problem”, such as “irregular menstruation (27%), abnormal vaginal bleeding (9.3%), amenorrhea (9.2%), menorrhagia (3.4%), dysmenorrhea (89.7%), and premenstrual symptoms (46.7%)” (Rafique and Al-Sheikh, 2018). Furthermore, endometriosis is estimated to affect “roughly 10% (190 million) of reproductive age women and girls globally” (World Health Organization [WHO], 2021). As of right now, the most common treatment plan for a wide variety of different menstrual disorders are birth control pills (Sole-Smith, 2019). However, oftentimes the pill does not treat the actual cause of the problem, but rather just masks the unpleasant side effects and is therefore somewhat of a “way of refusing to treat them” (Sole-Smith, 2019). Menstrual disorders among women are common, and yet there are very few specialized treatments for them. This is why scientists are now looking towards the evolution behind menstruation to gain more insight into how to treat the causes of these menstrual disorders. Jarrell (2018) states that “illnesses can be better understood as vulnerabilities associated with these evolutionary developments…while evolutionary aspects of these diseases indicate why such illnesses can occur, in some instances, they also provide a basis for treatment, prevention and future research direction.”
The second area of interest that can be improved by understanding the evolution behind menstruation is the social stigma surrounding periods. Historically, periods have held a negative connotation. Aristotle saw menstruation as an outward sign of female inferiority, and a nineteenth-century Scottish gynecologist was quoted saying ‘young girls should not play music or read serious books because it makes much mischief with their menstrual cycle’ (Maybin and Critchley, 2015). These negative associations tied with periods are “inextricably linked to the lower social position of women in society” (Maybin and Critchley, 2015). Even now, young girls are taught to be ashamed of this natural process. When a group of 12-15 year old girls were interviewed and asked how they felt about their period, the collective answer was that it was “embarrassing, shameful, and something to be hidden”, so much so that they even felt uncomfortable saying the word “period” (Burrows and Johnson, 2005). The rest of society wasn’t open to discussing menstruation either, as the girl’s school deemed it a “‘hidden curriculum’”, with the Head Teacher calling it a “‘sensitive topic’” and their male classmates reportedly insensitively laughing whenever menstruation did pop up in discussion (Burrows and Johnson, 2005). Because of these findings and information from other sources, the authors “argue that meanings attached to menarche and menstruation are constructed by developing and changing, context specific, socio‐cultural representations and practices; therefore it is these which need to be challenged and disrupted if girls' and women's experiences are to change for the better” (Burrows and Johnson, 2005). I believe a way to challenge society’s view of periods is through better education, including why menstruation happens in the first place. To be completely honest, I think periods are weird. It is sort of weird that we bleed for roughly a week every month. Like many other “weird” natural processes that humans didn’t have an immediate explanation for, such as the changing seasons and electricity, people harbored a fear towards menstruation and created myths to try and explain it. Unfortunately, this fear has been perpetuated for far too long. Just as we’re now able to explain seasons and electricity through science, we can also explain menstruation. It’s no longer a scary, secret process shrouded in mystery. Therefore, I am hopeful that the more people who are educated about the evolution behind menstruation, and about other topics regarding the menstrual cycle, the less taboo and stigmatized periods will be.
Lastly, I would like to switch directions for a minute and close this post with a challenge to focus on how this information can help you individually, rather than the broad societal impacts. Most likely at one point or another, you have hated being a person with a uterus. Maybe you have wished you could just rip it out. That all it causes you is pain and annoyance and problems. You have simplified your uterus to a problem. And now I want you to really think about why you have thought this. Obviously, there are justifiable reasons. Believe me, I have had my fair share of cramps and mood swings and all the other less-than-ideal issues. But I want you to consider a more sneaky reason that just adds to the self-hatred: internalized misogyny. From youth, we are taught that our periods are something to be ashamed of. Doesn’t it make sense that all of this negative rhetoric has compiled so much over the years that we have just been indoctrinated to hate our bodies even more than we recognize? If you still don’t agree with me and think the pain and annoyance are still the main reason you hate your period, consider this: if you had your period in a society that truly cared about your body, invested in research and medicine for your reproductive health, and made accommodations to support you through the bad days, would you still hate it so much? Women’s bodies are expected to function the same as men’s, when biologically this just cannot happen. That doesn’t mean menstruator’s bodies are worse or better, just different. But through our patriarchal society that is centered around and made for men, the differences become a negative thing. We should not have to hate our bodies simply because they function differently from a man’s. To finish this blog off, I would like to challenge you to one more thing. I would like you to show a little more love to your uterus and its menstrual cycle. I know that on some days this will be nearly impossible to do, especially when she is cramping and making your hormones rage. But the way I like to imagine it is as the ocean and its waves, continually ebbing and flowing. Some days it is calm and gentle, other days violent and angry, but always swelling and waning in a cyclical pattern. And all you can do is float on top of these waves, bobbing along with them. These peaks and dips are natural, so the best thing to do is to treat yourself with kindness, gentleness, and understanding. And just as the ocean and all of its different moods is a beautiful thing, hopefully, you can see that the menstrual cycle is also a beautiful, complex process that your body over millions of years has evolved to be able to do.
References
Burrows1, A., & Johnson, S. (2005). Girls’ experiences of menarche and menstruation. Journal of Reproductive & Infant Psychology, 23(3), 235–249. https://doi.org/10.1080/02646830500165846
Endometriosis. (2021, March 31). World Health Organization. https://www.who.int/news-room/fact-sheets/detail/endometriosis
Jarrell, J. (2018). The significance and evolution of menstruation. Best practice & Research Clinical Obstetrics & Gynaecology, 50, 18-26. https://doi- org.ezproxy.lib.ou.edu/10.1016/j.bpobgyn.2018.01.007
Maybin, J. A., & Critchley, H. O. D., (2015). Menstrual physiology: implications for
endometrial pathology and beyond. Human Reproduction Update, 21(6), 748– 761 doi:10.1093/humupd/dmv038
Ng, S. W., Norwitz, G. A., Pavlicev, M., Tilburgs, T., Simón, C., & Norwitz, E. R. (2020). Endometrial Decidualization: The Primary Driver of Pregnancy Health.
International Journal of Molecular Sciences, 21(11), 4092. https://doi.org/10.3390/ijms21114092
Rafique, N., & Al-Sheikh, M. H. (2018). Prevalence of menstrual problems and their association with psychological stress in young female students studying health sciences. Saudi Medical Journal, 39(1), 67–73. https://doi.org/10.15537/smj.2018.1.21438
Sole-Smith, V. (2019). The Point of a Period. Scientific American, 320(5), 33–40.