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An Eye-Opening (And Slightly Disturbing) Explanation To Why Women Get Their Period

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The theory of evolution has gradually come to explain nearly everything about human biology and even psychology. While there are people who might not be willing to accept it, explanations based on it turn out to be fairly accurate, and interesting. For those who might have wondered how evolution can explain why women menstruate, here’s a Quora thread with some pretty interesting answers. Do let us know what you think or have read about in the comments below.

This is the brilliant answer that Suzanne Sadedin, Ph.D. in evolutionary biology from Monash University, gave:

The answer to this question is one of the most illuminating and disturbing stories in human evolutionary biology, and almost nobody knows about it. And so, O my friends, gather close, and hear the extraordinary tale of:

HOW THE WOMAN GOT HER PERIOD

Contrary to popular belief, most mammals do not menstruate. In fact, it’s a feature exclusive to the higher primates and certain bats. What’s more, modern women menstruate vastly more than any other animal. And it’s bloody stupid (sorry). A shameful waste of nutrients, disabling, and a dead giveaway to any nearby predators. To understand why we do it, you must first understand that you have been lied to, throughout your life, about the most intimate relationship you will ever experience: the mother-fetus bond.

Isn’t pregnancy beautiful? Look at any book about it. There’s the future mother, one hand resting gently on her belly. Her eyes misty with love and wonder. You sense she will do anything to nurture and protect this baby. And when you flip open the book, you read about more about this glorious symbiosis, the absolute altruism of female physiology designing a perfect environment for the growth of her child.

If you’ve actually been pregnant, you might know that the real story has some wrinkles. Those moments of sheer unadulterated altruism exist, but they’re interspersed with weeks or months of overwhelming nausea, exhaustion, crippling backache, incontinence, blood pressure issues and anxiety that you’ll be among the 15% of women who experience life-threatening complications.

From the perspective of most mammals, this is just crazy. Most mammals sail through pregnancy quite cheerfully, dodging predators and catching prey, even if they’re delivering litters of 12. So what makes us so special? The answer lies in our bizarre placenta. In most mammals, the placenta, which is part of the fetus, just interfaces with the surface of the mother’s blood vessels, allowing nutrients to cross to the little darling. Marsupials don’t even let their fetuses get to the blood: they merely secrete a sort of milk through the uterine wall. Only a few mammalian groups, including primates and mice, have evolved what is known as a “hemochorial” placenta, and ours is possibly the nastiest of all.

Inside the uterus we have a thick layer of endometrial tissue, which contains only tiny blood vessels. The endometrium seals off our main blood supply from the newly implanted embryo. The growing placenta literally burrows through this layer, rips into arterial walls and re-wires them to channel blood straight to the hungry embryo. It delves deep into the surrounding tissues, razes them and pumps the arteries full of hormones so they expand into the space created. It paralyzes these arteries so the mother cannot even constrict them.

What this means is that the growing fetus now has direct, unrestricted access to its mother’s blood supply. It can manufacture hormones and use them to manipulate her. It can, for instance, increase her blood sugar, dilate her arteries, and inflate her blood pressure to provide itself with more nutrients. And it does. Some fetal cells find their way through the placenta and into the mother’s bloodstream. They will grow in her blood and organs, and even in her brain, for the rest of her life, making her a genetic chimera.

This might seem rather disrespectful. In fact, it’s sibling rivalry at its evolutionary best. You see, mother and fetus have quite distinct evolutionary interests. The mother ‘wants’ to dedicate approximately equal resources to all her surviving children, including possible future children, and none to those who will die. The fetus ‘wants’ to survive, and take as much as it can get. (The quotes are to indicate that this isn’t about what they consciously want, but about what evolution tends to optimize.)

There’s also a third player here – the father, whose interests align still less with the mother’s because her other offspring may not be his. Through a process called genomic imprinting, certain fetal genes inherited from the father can activate in the placenta. These genes ruthlessly promote the welfare of the offspring at the mother’s expense.
How did we come to acquire this ravenous hemochorial placenta which gives our fetuses and their fathers such unusual power? Whilst we can see some trend toward increasingly invasive placentae within primates, the full answer is lost in the mists of time. Uteri do not fossilize well.

The consequences, however, are clear. Normal mammalian pregnancy is a well-ordered affair because the mother is a despot. Her offspring live or die at her will; she controls their nutrient supply, and she can expel or reabsorb them any time. Human pregnancy, on the other hand, is run by committee – and not just any committee, but one whose members often have very different, competing interests and share only partial information. It’s a tug-of-war that not infrequently deteriorates to a tussle and, occasionally, to outright warfare. Many potentially lethal disorders, such as ectopic pregnancy, gestational diabetes, and pre-eclampsia can be traced to mis-steps in this intimate game.

What does all this have to do with menstruation? We’re getting there.

From a female perspective, pregnancy is always a huge investment. Even more so if her species has a hemochorial placenta. Once that placenta is in place, she not only loses full control of her own hormones, she also risks hemorrhage when it comes out. So it makes sense that females want to screen embryos very, very carefully. Going through pregnancy with a weak, inviable or even sub-par fetus isn’t worth it.

That’s where the endometrium comes in. You’ve probably read about how the endometrium is this snuggly, welcoming environment just waiting to enfold the delicate young embryo in its nurturing embrace. In fact, it’s quite the reverse. Researchers, bless their curious little hearts, have tried to implant embryos all over the bodies of mice. The single most difficult place for them to grow was – the endometrium.

Far from offering a nurturing embrace, the endometrium is a lethal testing-ground which only the toughest embryos survive. The longer the female can delay that placenta reaching her bloodstream, the longer she has to decide if she wants to dispose of this embryo without significant cost. The embryo, in contrast, wants to implant its placenta as quickly as possible, both to obtain access to its mother’s rich blood, and to increase her stake in its survival. For this reason, the endometrium got thicker and tougher – and the fetal placenta got correspondingly more aggressive.

But this development posed a further problem: what to do when the embryo died or was stuck half-alive in the uterus? The blood supply to the endometrial surface must be restricted, or the embryo would simply attach the placenta there. But restricting the blood supply makes the tissue weakly responsive to hormonal signals from the mother – and potentially more responsive to signals from nearby embryos, who naturally would like to persuade the endometrium to be more friendly. In addition, this makes it vulnerable to infection, especially when it already contains dead and dying tissues.

The solution, for higher primates, was to slough off the whole superficial endometrium – dying embryos and all – after every ovulation that didn’t result in a healthy pregnancy. It’s not exactly brilliant, but it works, and most importantly, it’s easily achieved by making some alterations to a chemical pathway normally used by the fetus during pregnancy. In other words, it’s just the kind of effect natural selection is renowned for: odd, hackish solutions that work to solve proximate problems. It’s not quite as bad as it seems, because in nature, women would experience periods quite rarely – probably no more than a few tens of times in their lives between lactational amenorrhea and pregnancies.

We don’t really know how our hyper-aggressive placenta is linked to the other traits that combine to make humanity unique. But these traits did emerge together somehow, and that means in some sense the ancients were perhaps right. When we metaphorically ‘ate the fruit of knowledge’ – when we began our journey toward science and technology that would separate us from innocent animals and also lead to our peculiar sense of sexual morality – perhaps that was the same time the unique suffering of menstruation, pregnancy and childbirth was inflicted on women. All thanks to the evolution of the hemochorial placenta.

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An ambassador and trained facilitator under Eco Femme (a social enterprise working towards menstrual health in south India), Sanjina is also an active member of the MHM Collective- India and Menstrual Health Alliance- India. She has conducted Menstrual Health sessions in multiple government schools adopted by Rotary District 3240 as part of their WinS project in rural Bengal. She has also delivered training of trainers on SRHR, gender, sexuality and Menstruation for Tomorrow’s Foundation, Vikramshila Education Resource Society, Nirdhan trust and Micro Finance, Tollygunj Women In Need, Paint It Red in Kolkata.

Now as an MH Fellow with YKA, she’s expanding her impressive scope of work further by launching a campaign to facilitate the process of ensuring better menstrual health and SRH services for women residing in correctional homes in West Bengal. The campaign will entail an independent study to take stalk of the present conditions of MHM in correctional homes across the state and use its findings to build public support and political will to take the necessary action.

Saurabh has been associated with YKA as a user and has consistently been writing on the issue MHM and its intersectionality with other issues in the society. Now as an MHM Fellow with YKA, he’s launched the Right to Period campaign, which aims to ensure proper execution of MHM guidelines in Delhi’s schools.

The long-term aim of the campaign is to develop an open culture where menstruation is not treated as a taboo. The campaign also seeks to hold the schools accountable for their responsibilities as an important component in the implementation of MHM policies by making adequate sanitation infrastructure and knowledge of MHM available in school premises.

Read more about his campaign.

Harshita is a psychologist and works to support people with mental health issues, particularly adolescents who are survivors of violence. Associated with the Azadi Foundation in UP, Harshita became an MHM Fellow with YKA, with the aim of promoting better menstrual health.

Her campaign #MeriMarzi aims to promote menstrual health and wellness, hygiene and facilities for female sex workers in UP. She says, “Knowledge about natural body processes is a very basic human right. And for individuals whose occupation is providing sexual services, it becomes even more important.”

Meri Marzi aims to ensure sensitised, non-discriminatory health workers for the needs of female sex workers in the Suraksha Clinics under the UPSACS (Uttar Pradesh State AIDS Control Society) program by creating more dialogues and garnering public support for the cause of sex workers’ menstrual rights. The campaign will also ensure interventions with sex workers to clear misconceptions around overall hygiene management to ensure that results flow both ways.

Read more about her campaign.

MH Fellow Sabna comes with significant experience working with a range of development issues. A co-founder of Project Sakhi Saheli, which aims to combat period poverty and break menstrual taboos, Sabna has, in the past, worked on the issue of menstruation in urban slums of Delhi with women and adolescent girls. She and her team also released MenstraBook, with menstrastories and organised Menstra Tlk in the Delhi School of Social Work to create more conversations on menstruation.

With YKA MHM Fellow Vineet, Sabna launched Menstratalk, a campaign that aims to put an end to period poverty and smash menstrual taboos in society. As a start, the campaign aims to begin conversations on menstrual health with five hundred adolescents and youth in Delhi through offline platforms, and through this community mobilise support to create Period Friendly Institutions out of educational institutes in the city.

Read more about her campaign. 

A student from Delhi School of Social work, Vineet is a part of Project Sakhi Saheli, an initiative by the students of Delhi school of Social Work to create awareness on Menstrual Health and combat Period Poverty. Along with MHM Action Fellow Sabna, Vineet launched Menstratalk, a campaign that aims to put an end to period poverty and smash menstrual taboos in society.

As a start, the campaign aims to begin conversations on menstrual health with five hundred adolescents and youth in Delhi through offline platforms, and through this community mobilise support to create Period Friendly Institutions out of educational institutes in the city.

Find out more about the campaign here.

A native of Bhagalpur district – Bihar, Shalini Jha believes in equal rights for all genders and wants to work for a gender-equal and just society. In the past she’s had a year-long association as a community leader with Haiyya: Organise for Action’s Health Over Stigma campaign. She’s pursuing a Master’s in Literature with Ambedkar University, Delhi and as an MHM Fellow with YKA, recently launched ‘Project अल्हड़ (Alharh)’.

She says, “Bihar is ranked the lowest in India’s SDG Index 2019 for India. Hygienic and comfortable menstruation is a basic human right and sustainable development cannot be ensured if menstruators are deprived of their basic rights.” Project अल्हड़ (Alharh) aims to create a robust sensitised community in Bhagalpur to collectively spread awareness, break the taboo, debunk myths and initiate fearless conversations around menstruation. The campaign aims to reach at least 6000 adolescent girls from government and private schools in Baghalpur district in 2020.

Read more about the campaign here.

A psychologist and co-founder of a mental health NGO called Customize Cognition, Ritika forayed into the space of menstrual health and hygiene, sexual and reproductive healthcare and rights and gender equality as an MHM Fellow with YKA. She says, “The experience of working on MHM/SRHR and gender equality has been an enriching and eye-opening experience. I have learned what’s beneath the surface of the issue, be it awareness, lack of resources or disregard for trans men, who also menstruate.”

The Transmen-ses campaign aims to tackle the issue of silence and disregard for trans men’s menstruation needs, by mobilising gender sensitive health professionals and gender neutral restrooms in Lucknow.

Read more about the campaign here.

A Computer Science engineer by education, Nitisha started her career in the corporate sector, before realising she wanted to work in the development and social justice space. Since then, she has worked with Teach For India and Care India and is from the founding batch of Indian School of Development Management (ISDM), a one of its kind organisation creating leaders for the development sector through its experiential learning post graduate program.

As a Youth Ki Awaaz Menstrual Health Fellow, Nitisha has started Let’s Talk Period, a campaign to mobilise young people to switch to sustainable period products. She says, “80 lakh women in Delhi use non-biodegradable sanitary products, generate 3000 tonnes of menstrual waste, that takes 500-800 years to decompose; which in turn contributes to the health issues of all menstruators, increased burden of waste management on the city and harmful living environment for all citizens.

Let’s Talk Period aims to change this by

Find out more about her campaign here.

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A former Assistant Secretary with the Ministry of Women and Child Development in West Bengal for three months, Lakshmi Bhavya has been championing the cause of menstrual hygiene in her district. By associating herself with the Lalana Campaign, a holistic menstrual hygiene awareness campaign which is conducted by the Anahat NGO, Lakshmi has been slowly breaking taboos when it comes to periods and menstrual hygiene.

A Gender Rights Activist working with the tribal and marginalized communities in india, Srilekha is a PhD scholar working on understanding body and sexuality among tribal girls, to fill the gaps in research around indigenous women and their stories. Srilekha has worked extensively at the grassroots level with community based organisations, through several advocacy initiatives around Gender, Mental Health, Menstrual Hygiene and Sexual and Reproductive Health Rights (SRHR) for the indigenous in Jharkhand, over the last 6 years.

Srilekha has also contributed to sustainable livelihood projects and legal aid programs for survivors of sex trafficking. She has been conducting research based programs on maternal health, mental health, gender based violence, sex and sexuality. Her interest lies in conducting workshops for young people on life skills, feminism, gender and sexuality, trauma, resilience and interpersonal relationships.

A Guwahati-based college student pursuing her Masters in Tata Institute of Social Sciences, Bidisha started the #BleedwithDignity campaign on the technology platform Change.org, demanding that the Government of Assam install
biodegradable sanitary pad vending machines in all government schools across the state. Her petition on Change.org has already gathered support from over 90000 people and continues to grow.

Bidisha was selected in Change.org’s flagship program ‘She Creates Change’ having run successful online advocacy
campaigns, which were widely recognised. Through the #BleedwithDignity campaign; she organised and celebrated World Menstrual Hygiene Day, 2019 in Guwahati, Assam by hosting a wall mural by collaborating with local organisations. The initiative was widely covered by national and local media, and the mural was later inaugurated by the event’s chief guest Commissioner of Guwahati Municipal Corporation (GMC) Debeswar Malakar, IAS.

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