By Franca Parianen
An excerpt from Parianen's book, Hormongesteuert ist immerhin selbstbestimmt. Loosely translated as, Being controlled by your hormones is one way of being in control, or It's just hormones, they know what they're doing.
In the beginning, there was a lot of confusion
…then at some point, it turned to life.
Conception is when the trouble starts. The building blocks of our lives have barely even been set in motion, but we’re already getting caught up. In the expectations, or none-expectations of all parties involved, in their assumptions about what just happened and the roles they played in it, in the importance of the chromosomes that just merged and the way they will define our lives. Entire religions could spend centuries fighting about our blob of cells and the question of when it will be touched by the divine, blessed with an immortal soul, or from a rebirth perspective, sigh and think “Not again.”. A lot of politicians will gladly weigh in on that. But right now, we’re not even talking about the metaphysics of it, the question of what life is and where it begins. We’re talking about the physical realities of conception and frankly that is mystifying enough.
The way we stumble into this world is something of an enigma and that might come as a surprise. After all, the educational videos we giggled our way through in primary school seemed quite clear (well, maybe not in Utah). Most of us still carry their lively images around to this day: A big round egg, looming, like a planet on some uterine sky, waiting to be explored. Fittingly, sperms approach it like tiny rocket ships, racing for their price. As with space travel, the only one to leave an impression, is the first one to set foot (I’m potentially remembering this a bit more vividly). The miracle of conception, leaving us with the fulfilling notion that, at least once in our lives we outran everybody else. If your racing skills are anything as impressive as mine, that is a comforting thought. In general, it’s a compelling image and obviously true in its basic coordinates. The egg, the sperms, the fertilization. Nevertheless, it leaves ample room for misconception. And we exploit every inch of it.
First of all, speed isn’t everything. In fact, in a lot of species it’s barely even relevant, since sperm is collected over longer periods of time. Hence, grade-A sperm doesn’t only reach its goal at the speed of light, it knows how to survive there for a while. Improvise, adapt, overcome. Nature has good reason to value those qualities, since longer-living sperm might indicate healthier sperm, or even make for humans with a longer-living fertility.
More importantly, our fixation on speed is part of a much bigger misconception: The shockingly passive role of the egg. That in turn is part of some even biggest problems: Myths and misunderstandings, pseudoscience and sexism. The twin disasters that accompany every topic of reproductive health.
But let’s start at the beginning: First of all, it’s quite presumptuous to assume the oocyte just looms. Expectantly waiting around, dinner in the oven. Instead, it’ll have you know, the oocyte follows its own busy time schedule. A tighter one in fact, than that of the sperms. While the latter can live comfortably for a few days, the former only has a time window of about 24-48 hours to get to business. And as we know, those hours are scheduled a while ahead in its monthly planner. Consequentially, the sperm cells, who are indeed always at the ready, will often have to take a seat, before the oocyte makes its big entrance. Secondly, the oocyte will hardly welcome just any sperm, let alone the first one it encounters. It takes time to open up. Protected by thick layers of tissue, the egg watches hundreds of sperm cells bump their head in, until finally the outside walls rub against each other, loosen, and turn permeable enough for one lucky winner to wiggle its way through. It’s less about speed than about commitment.
Admittedly, being bombarded by an entourage of courtiers, sighing and giving in’ might still be considered somewhat passive. As a general rule, no approach to mating should count as progressive, if it could be featured by Jane Austen. Including the part, where the winner is the fortunate one, who has been ducking behind the others all along. However, the egg’s role isn’t just to lean back and watch the sperm cells bring it on. Quite the opposite: At the point of conception, both our gametes have lived quite an exciting live to look back to – albeit they’ve lived it on different time scales.
While sperm gets replenished inside the testicles about once every two months, the precursors of human eggs grow with us. Whoever gave birth to you, carried a part of you even before they were born. The notion that parts of us used to swim around inside our grandmother is a bit awkward, but more importantly, it’s a reason why her trauma, nutrition or medicine might affect you to this day. And while this information could potentially change our view of our medical history and our very selves, right now it’s mostly lead to some unhealthy fixation and a number of YouTube videos entitled "All your eggs will be rotten at thirty!" Remarkably, this idea of fertility ending in a steep cliff somewhere around that age, is based on the extremely representative data sample of…French farmers in the 1700s. We really can’t tell, why 1/3 of the women in this dataset stopped procreating after 35, but for all we know, they might have scurvies. Been busy planning a revolution. Just French people things. In any case, this study is a great example of what happens to data science, if you don’t actually care about the nature of your data. More modern numbers turn the cliff into a much gentler hill: Indeed 82% of women trying for a baby between 35 and 39 will post an inspirational picture captioned “We’re expecting!” within the next year. Even more recent results indicate that the number of eggs might not be entirely finite. Ovaries could produce some additional oocytes over the years. It’s something fertility doctors will hopefully be able to make use of in the future.
But while they are at it, more modern approaches will of course also look at the male side of things. Fertility is very much a topic for all genders and also men’s testosterone levels decline with age - starting in their mid-thirties. But before you start despairing and/or buying a motorcycle, keep in mind, its only 1 percent per year. You could have steeper dumps from being in a loving relationship. A much more interesting worry is the decline in sperm quality among industrialized countries, which some studies imply and which has equally been featured in a number of YouTube videos. Mostly those yelling about gay frogs. Tucker Carlson has discussed the issue as well, although focusing less on gay frogs and more on the immanent destruction of manliness itself (next Tuesday at the latest). Both pundits affirm that populism truly is the alcohol to every debate: It might look like a solution, but in reality, you’re now somehow more wrong, aggressive and louder. A much more promising solution would feature environmental protection laws preventing endocrine disruptors in industry, plastic and agriculture. Especially, where we might risk prenatal exposure to these substances. But well.
In sum, our gametes might live on different time scales, but they both make it through our thirties. Apart from that, they are prone to similar limitations, fertility issues and outside influences. Additionally: They both face tough competition.
In line with our overall pretty passive view of the oocyte, we tend to believe that it has little agency in the process of conception. After waiting around its whole life for the signal to mature, it’ll just answer the call, walk through the door and get ready to do some more waiting. But in truth, our oocyte had to fight its way onto the big stage, albeit off screen. Every month, several follicles receive that same call, all of them put their shoes on, to prepare for the journey, and in most cases, only one of them survives. Maturation is a tough battleground. Rightfully so, given that pregnancy is quite a drain on the system, so it makes sense for our bodies to carefully weed out any potential partners in this operation no matter their sex. On the uterine side, the surviving fighter may call itself the all-compelling graafian follicle. Named after the Dutch Anatomist Reinier de Graaf. And in true period dramatic fashion, in some rare occasions, the Graaf follicle has a twin, in which case, so do we. But for the most part, the Graafian follicle has outlasted and ridded itself of much of the competition. It has worked as least as hard on being here as the sperm. Now that it’s finally here, it’s not going to mess around. Hence the thick walls.
It makes sense for the oocyte to be the picky one. After all, it’s quite literally the one with a choice. By comparison, a single sperm cell has but one life to give and would rather not let it go to waste. That is to say if there’s a reason for a sperm cell to have a good hard look at an egg, change its mind and turn around, we haven’t found it yet. Meanwhile, the uterine environment is a lot more creative. Across species female’s sexual selection has evolved to lead unwanted sperm cells astray, store it in remote areas or just eject it right away. In turn sperm has evolved to outlast and push aside competitors. It’s an arms race. While humans unfortunately lack most of the more innovative all-natural abilities of anti-contraception, the whole atmosphere inside the Uterus is one of “Parkour!” The acidity can be dangerously high and the density of the mucus can make swimming a pretty hard task. Not to forget, an immune system whose normal response to intruders is “attack”. The likelihood of this response is greatly enhanced, if said immune system has identified sperms as a cause of prior infection (it doesn’t distinguish between correlation and causation very well). To be fair, sperm cells are seen as outsiders even inside the testicles. The only reason the immune system doesn’t attack them in there is, because testosterone’s immunosuppressive features are holding it back. In exchange, people with high testosterone turn very dramatic when they have a cold.
Notably the notion that sperms aren’t choosy is not meant to be generalized to the organism level. Not in all species at least. Sure, across most of them, females get to be the choosing sex, whereas males get to be the one with the pretty feathers and fashionable dance moves. But it turns out humans are not in fact birds. That is to say, men don’t have a habit of creating offspring, then forgetting about it and running off into the wild. If they do, it’s evolutionary questionable choice, since the prolonged postnatal brain development of said offspring demands for an amount of care that is almost impossible for one parent to carry. Instead, our species has been co-parenting for ages (well, up until the fifties), with friendly support from grandparents, aunts, uncles, and childless friends who just enjoy the show. Father’s traditional involvement in these family bonds is still reflected in our bodies today, reflected in the significant hormonal changes men undergo with parenthood. With the main difference that most men need to actually see and experience their child to inform their hormone system of that transition, while people with a uterus tends to get the news from their placenta. In any case fatherhood demands a lot more commitment than just ‘spreading the sperm’.
Similarly, the uterus defensive selectivity is often misunderstood as a sex difference of one who wants sex and one who has a headache. Or misconstrued that way, based on a long history of misogynistic ideas of virginity, prudence, shame and sin. Think about how we talk about our hormones for example: While testosterone has a well-known reputation as a sex hormone in the literal sense, estradiol is mostly seen as causing…emotions. Possible parking impairment. Similarly, there’s a whole industry built on the idea that women’s sexual desires are to 50 % absent or dysfunctional. Which, if anything, is a weird association of responsibility. When 52 % of the audience was displeased with the finally of Game of Thrones, we certainly didn’t put the blame on them. More importantly the claim is based on a bogus study, whose authors later had to admit a conflict of interest. More exactly, this study classified anyone as dysfunctional who expressed doubt in there ‘sexual performance’, or a lack of sexual interest, at any time in the past two months. The resulting number was 43 %. Notably about 38 % of men expressed the same and in any case no one was asked, if they were suffering from it.
Fortunately, science – if done right - can’t just perpetrate prejudice it can also help us get rid of it. If we go back to the sex hormones for example, it has taught us that testosterone and estradiol actually share a lot of behavioral effects. Not surprisingly given that both support a common goal: Letting the gametes mingle – and that’s a lot harder, if you don’t leave your house. As a result, both sex hormones increase our taste for risky decisions, our ability to overcome anxieties and our inflated sense of our own ability (how else would you flirt?). Estradiol actually helps us recover from trauma. Regarding our bodies, both of those sex hormones tend to put on a show. By enhancing features that are generally thought to be attractive - wide shoulders or hips, thick lips or strong jar- and those that make us look somewhat alive -blushed cheeks, widened pupils, shiny hair. After usage, the remainders of those hormones are transported to our sweat glands and processed by bacteria in your armpits, adding a nice smell. Children don’t yet produce sex hormones, which is why their gym cabins just smell like shoes and forgotten sportswear. While we’re at it, estradiol’s most poignant role isn’t about emotions or parking, but neuroplasticity and language development. And whatever the humorous women’s editions of sexy calendars editions say, estradiol isn’t interested in fully clothed man vacuum the ceiling. It likes naked bodies. Thank you very much. Differently put: Estradiol rises before ovulation as well as in response to pornographic imagery and enhances our interest in cues of masculinity, beards and dark voices. By contrast, prenatal testosterone might increase women’s interest in women.
All in all, the gametes have a mutual interest in reproduction, much like the sexes have a mutual interest (or disinterest) in sex and the only reason to think of human sexuality as a battle, is if you want to think of yourself as part of the long tradition of unwanted males. In which case I hope the women around you think of themselves as praying mantis. For everybody else, procreation is a cooperative challenge, which leaves our uterus with the difficult task to design an environment that’s challenging but not impossible. Like one of those Da Vinci code puzzles that are hard enough to go unsolved for centuries but also simple enough to be solved by the protagonist and half of the audience.
In ideal conditions, the mucus thins to facilitate swimming at the right time of the months. And melatonin, the nightly hormone, helps to activate the sperm cells and send them on their way (“zooooom”). The chemical processes involved might even restore some of the oxidative damage the gametes might carry – an important indicator for our later health. Another way of supporting the courtiers is by guiding their way. As it turns out, sperm cells are not very well versed in female anatomy or orientation. About 4/5th of them will not end up where they wanted to go (nor where they needed to be), and thus, any piece of advice on the whereabouts of the eggs is greatly appreciated. Fortunately, the uterus can provide such advice through chemical cues. Few people are aware of that, but a big part of our olfactory cells is carried in our testicles. (Much like taste buds in the uterus might play an important role in starting the process of birth.) The vagina in turn releases pheromones called korpulines precisely for this context. It’s still up to debate, whether humans can consciously perceive the accompanying smell, but at least, dogs probably can, which is why you now need to try to wiggle their nose from under your skirt while not revealing to much of your H & M underwear. But they’d respond the same way, if you’re just on your period or breastfeeding. So, there’s that.
Even the egg can release chemo-attractants, to help guide the sperms on their way. Although, these seem to attract some people’s sperm cells more than others. And, before you ask: They are not necessarily your partner’s. A match by immune markers is a more likely choice for your egg to make than one by Tinder, so when you chose your partner, your egg might beg to differ. It’s a potential fertility problem that research has only recently discovered and will hopefully soon get a hold of. In the meantime, we can refer to our lucky winner as “the chosen one”.
So, speed isn’t everything and neither lust nor competition are limited to the male side of things. A great way to drive home our newfound multilayered view, is the look at biological sex. After all, that too seemed a lot easier in biology class. You’ll probably recall that an XY chromosome is what’s commonly associated with male sex, while a double X tends up to end up on the female side (terms and conditions apply, but more on that later). Since each parent contributes one chromosome and the egg’s choices are mostly limited to an X the biological sex in large part depends on the sperm: Either a Y or an X. So, what we’ve taken away from biology class is that the father determines the sex, and frankly that is a step forward from Henry the 8th approach of “Behead the woman”. It’s still a misconception though, not just because the person who carries the sperm might not identify as “the father”, but also because chromosomal sex is actually influenced by a whole bunch of factors we’re only just beginning to understand – including some we’ve gotten to know in the last paragraph. There’s the speed for example: XY sperm tends to be a bit lighter and thus faster (a Y has 3 arms an X has 4, so Y sperm). If the oocyte is ready, they have a better shot. By comparison XX sperms survives longer, so if the oocyte takes its time, they’ll be alright. They brought folding chairs. A baby’s sex is thus also determined by the timing of conception, which in turn is determined by whoever decided to pause Netflix first. Another important factor is the uterine environment, which is influenced by salty nutrition, immune responses, potentially stress levels. Times of war and famine birth fewer boys and somehow Anesthetists too. I swear I’m not making this up.
In sum, a choice for which we’ve traditionally blamed women, then considered a man’s job, is actually far more complicated than that. Of course, the topic of sex and gender itself opens up a whole different can of worms. Or a box of Pandora’s depending on how you look at it. From what we know, there are XYs and XXs and while the former would evolve to become men, the others would evolve to earn 19 percent less. Clear and simple. A big part of our lives decided right there and then at the second of conception. For a long time, this will be the first thing people ask when they learn about our existence. Or maybe the second, right after “When is it due?” It’ll be reflected in the names our parents think about, the way they describe our kicks and the color that’s released, when our gender reveal, starts a forest fire. Although, by that time, the journey of our sexual development has already progressed quite a bit and the answer from our chromosomes might be a different one than what you see on the ultrasound, or even what’s going on inside your head. Because all these things are related, but they are never the same. Like with mood: Can mood be fully explained by biological concepts? No, because work stress. But does that mean biology has no part in it? Again, no because depression. Likewise, chromosomal sex, has a strong impact on our biological sex and an at least considerable impact on our later perceived gender. In theory the Y chromosomes will code for the formation of testicles, which will then produce testosterone, which will push body and brain towards masculinization, so that all these factors fit together smoothly. In that case the only surprise should be that for much of its work, testosterone slips into a more comfortable form: That of estradiol. As it turns out, our two sex hormones are just one carbon electron away from each other. The brain can easily transform T into E and it does so all the time. Mostly to mess with people who say sex is a binary construct. Or with scientists who administer testosterone just to measure an effect of estradiol. In fact, estradiol is often thought to be the dominant sex hormone in men’s brains and in many species, it seems to be the one responsible to develop male brains and sexuality. Think about that next time you hear birds chirping. It’s another reason, why testosterone and estradiol aren’t in fact polar opposites. By comparison, the development of female fetuses barely needs any sex hormones, because ‘female’ is kind of our bodies default mode, which is why men, too, get to enjoy nipples.
So far, so complex, but the longer you look at it, the more obvious it becomes, that our genetic code is more what you’d call guidelines. There are many reasons why our bodies and brains might stray away from the developmental routes planned out by our chromosomes. One of them being that organ development is hard. Much like other bodily structures, sometimes genitalia just don’t evolve like intended, without it affecting our genetic make-up, or who we are as a person. Similarly, hormones need certain conditions to work. Testosterone needs a receptor to bind to a cell. If your receptors are dysfunctional, it’ll just linger around in front of the cell, awkwardly staring through a window and leaving after unfinished business. Masculinization of body and brain barely takes place, you’ll look female and there’s a good chance you’ll feel like it too. Alternatively, if your body lacks the enzyme that turns testosterone into its more active form dihydrotestosterone, only a small part of that masculinization will take place and the development of your male genitalia will have to wait for the hormone rushes of puberty, at which point they’ll come as quite a surprise. Biological sex isn’t a one-time event, it’s a development. Notably the developmental stages during which our body parts are shaped by these processes differ. Male genitalia evolve weeks into our development. Masculinization of the brain happens more than half a year into the pregnancy and even continues after birth. In the meantime, our hormone levels are constantly changing influenced by our own bodies and that of potential twins as well as that of the person carrying us in their womb. Their stress- and oxytocin-levels, immune reactions and antibodies. So whether or not we start out with a Y chromosome, resulting in testosterone-producing testicles, is really just part of the picture. If you want to get a glimpse at the variation, just look at the shoulder to hip ratio of the people around you – an indicator of early testosterone, or the waste to hip ratio- an indicator of estradiol exposure mostly later in life. Even the ratio of your 2nd to 4th digit is believed to be somewhat related to hormone exposure – with the index finger being more related to estradiol and the ring finger testosterone. If you average it across large numbers of people, you may find associations with character traits and each genders preferred psychiatric issues. In any case, these indicators show what different paths our hormones can take throughout our lifetime and often they relate to behavior. More importantly they change. Across the month, the seasons and even across the day. When we hit puberty parenthood or menopause. With our relationship status. Little is fixed, most things change, even the connections in our brain. So in short: Of course it’s a special moment, when the sex of our baby is announced through a small forest fire. But we should probably see this information as more of a working hypothesis. Guidelines not actual rules. And we should stop insisting on knowing better, desperately clawing to our ideas of two sexes, insisting on standing on the floor of the facts, while from a scientific perspective, our stand point looks suspiciously like the breeding ground of ignorance. Much like we insist on understanding conception, even if there’s still so much to learn, so much useful information to discover, if only we could stop filling the blanks with presumptions. When we come into this world kicking and screaming, we’re pretty much surrounded by expectations- some of which can be traced back to those few seconds of conception. But these are modern times. And modern science equips us with a unique chance to revisit those expectations and the baggage that comes with them. Liberating us, one pseudoscientific assumption at a time, till we reach the very beginning. Time to start with a clean slate.
Franca Parianen is a Berlin-based neuroscientist, speaker, and bestselling author. Her research focuses on the intersection of hormones, brain, and social behavior, or as she says: “Ideal for people with decision difficulties.”. As with most people who read Oliver Sacks at a young age, she got hooked on brain sciences right away, and that fascination never left her side.
After a short intermezzo resulting in a Bachelor of Politics, she eloped to the Netherlands to complete a Master in Neuroscience and subsequently a PhD. While working for the Max-Planck-Institute, she started science slamming – a "scicom" format in which scientists battle to present results in the most captivating way – presenting her findings around bars, clubs and medical conventions. As a science slammer, she has won numerous championships and prices and also spent a lot of weekends in German towns she doesn’t remember the names of.
In 2015 she decided to take off and see the world instead, until, in an abrupt turn of events, she was simultaneously contacted by a literary agent and stung by a bee. As of today, she published three books which were translated in four languages. She’s also allergic to bees.
Franca Parianen’s debut novel Woher soll ich wissen, was ich denke, bevor ich höre, was ich sage (How should I know what I think, before I hear what I say), was written on a crappy laptop in Havana, New York City, and on the river Mekong, and later published by Rowohlt.