Are We Still Dancing With the Moon?

What ancient stories, modern science and our own bodies can tell us about rhythm

I've been thinking about the Moon, with the massive Harvest Moon we had last week and the talk amongst my friends.

I haven’t suddenly started planning my life around lunar phases, but I have became curious about something. For thousands of years, humans have connected the Moon with women's bodies, menstruation, fertility, birth and eventually menopause. Somewhere along the way, particularly as medicine became increasingly scientific, much of that connection was relegated to mythology, folklore or the slightly uncomfortable category for some folk of "woo".

And yet our bodies evolved underneath that Moon.

For almost all of human history there were no electric lights, illuminated bathrooms, televisions or phones glowing beside our beds (if you keep a phone in your room at night could I recommend you invest in an alarm clock and leave it somewhere else- read Matthew Walker.)

There was bright daylight, proper darkness and a night sky that changed quite dramatically throughout the month. Humans lived within those changes rather than simply observing them.

So I started wondering whether there might be something interesting sitting between the old stories and modern science. Not proof that the Moon controls our bodies (although a little bit of me wanted there to be), but a bigger question about rhythm itself. What did our ancestors notice? What have we forgotten to notice? And what is science now beginning to understand about the extraordinary number of clocks ticking away inside us?

When medicine looked at the sky

Go back several hundred years and medicine, astronomy and astrology weren't separated into the tidy boxes we put them in today. Medieval and early modern physicians used astronomical and astrological calendars alongside their medical knowledge. Almanacs contained information about the movement of the Sun, Moon and planets, and one of the more extraordinary images that survives from this period is the Zodiac Man, a human body with different signs of the zodiac mapped across it.

The heavens were consulted when deciding when certain treatments should take place, particularly bloodletting. The body wasn't considered something separate from the world around it. It existed within a much larger system.

That doesn't mean those physicians always had the explanation right. They frequently didn't. But there is an important distinction between observation and explanation. Ancient people could notice something real without understanding the mechanism behind it, just as we can today.

And there is a little piece of that ancient relationship hiding in a word we still use.

Menstruation comes through the Latin menstruus, meaning monthly, from mensis, meaning month. If we travel further backwards through language, the words for Moon and month share ancient roots. The Greek mene means Moon and men means month. Long before the calendar hanging on your kitchen wall, the changing Moon was one of humanity's ways of marking the passage of time.

One complete lunar cycle takes approximately 29.5 days. It grows from the faintest sliver into a brilliant full Moon, gradually disappears and begins again. Against that visible rhythm, humans were also observing bodies that bled, conceived, grew babies and eventually stopped bleeding.

It isn't really all that difficult to understand why the two became so intertwined.

The stories we told before we could measure hormones

Before we could measure oestradiol, progesterone, luteinising hormone (a chemical messenger produced by the pituitary gland that controls reproductive function & sexual development) or melatonin, people watched.

They watched the seasons change, plants grow and die back, animals reproduce, women bleed and babies arrive. They watched the Sun disappear every evening and return every morning. Above them, the Moon slowly changed shape, disappeared completely and then somehow returned.

Those observations found their way into stories.

In ancient Greece, Selene wasn't simply a goddess associated with the Moon. She was the Moon, visualised and imagined travelling across the night sky in her chariot. Ancient writers connected lunar cycles with pregnancy and childbirth, partly because pregnancy itself could be understood and counted in lunar months.

Then there was Artemis. Over time, particularly in later Greek tradition, Artemis became increasingly associated with the Moon, and this is where the connection with women becomes more interesting. The Moon was visibly changing through a repeating cycle of waxing, fullness, waning and disappearance, while women were living through their own repeating cycles of bleeding, fertility, pregnancy, birth and renewal. Artemis sat somewhere amongst all of this. She was associated not only with the Moon and the wildness of the natural world, but with girls becoming women, fertility and childbirth. She accompanied women through some of the great transitions of the female body.

One of the stories surrounding her own birth even has the newborn Artemis helping her mother, Leto, deliver her twin brother Apollo. Whether anyone intended that story as an anatomical account is probably unlikely, but what interests me is how closely these ideas became woven together. The changing Moon, the female body, fertility, birth and transition weren't being placed into separate boxes. They were different expressions of a world that was understood to move in cycles.

And perhaps that is the important part. The Moon grows, becomes full, recedes and disappears, but it hasn't gone. It returns and begins again. A woman's reproductive life also moves through cycles within much larger cycles, from menstruation to pregnancy and postpartum, through perimenopause and eventually beyond menstruation altogether. They aren't the same cycles, and one doesn't prove that the other controls it, but you can understand why people looking upwards thousands of years ago saw a connection.

As Greek and later Roman traditions developed, Selene and Artemis also became increasingly connected with Hecate, the goddess associated with night, thresholds, crossroads and transitions.

Hecate particularly interests me when we start thinking about menopause because menopause is, quite literally, a transition from one physiological state into another. Modern medicine understandably describes much of that transition through what changes or ends. Ovulation ceases, menstruation stops, oestradiol and progesterone alter dramatically and natural fertility comes to an end.

The ancient stories give us another way of looking at transition. Instead of only asking what has finished, they also allow us to ask what comes next.

It would be very easy at this point to create a beautifully neat story in which every ancient civilisation saw the Moon as female and connected it with menstruation. They didn't. Across different cultures the Moon has been male as well as female, benevolent and dangerous, associated with fertility, sexuality, birth, death and transformation. I discovered when researching this topic for the blog that In some Aboriginal Australian traditions, for example, the Moon is male. Other traditions from different parts of the world connect lunar figures with fertility, pregnancy or menstruation in entirely different ways.

There isn't one ancient Moon story.

What there does seem to be, again and again, is an awareness of rhythm.

Imagine trying to understand your body without a clock, calendar, pregnancy test, hormone panel or period-tracking app. You would have had to pay attention. You would notice when things returned, when they disappeared and how long the spaces between them seemed to be.

Those stories aren't scientific evidence that the Moon controls women's bodies. They are something different. They are records of what human beings noticed, wondered about and considered significant enough to keep talking about.

And I think that is super important.

And perhaps this idea of women noticing one another's rhythms isn't entirely ancient history either.

I've lived in plenty of shared flats over the years, and I've experienced that strange thing where women's periods seem to start converging. You realise one person has started her period, then somebody else has, and after living together for a while it feels as though everyone's bodies have somehow begun keeping roughly the same time.

I'm certainly not the only woman who will tell you this. Ask a group of women who have lived together, travelled together or spent years working closely together and you're likely to hear similar stories. We notice it because it's happening in our own bodies, even if we don't necessarily know why.

And this is where lived experience and science can rub up against each other in a really interesting way.

In 1971, researcher Martha McClintock published a now-famous study suggesting that the menstrual cycles of women living together could become more closely aligned. The phenomenon became known as menstrual synchrony, or the McClintock effect. Later studies have challenged it, and there is still no convincing evidence that one woman's body somehow pulls another woman's menstrual cycle into line. Some researchers argue that cycles of slightly different lengths will naturally move together, overlap for a while and then drift apart again, creating what looks and feels like synchronisation.

And perhaps they're right.

But I also wonder whether we've been asking the wrong question.

Women living together don't just share a building. We often share light and darkness, mealtimes, late nights, early mornings, activity, stress, conversation and sleep patterns. Our bodies are receiving many of the same environmental cues at roughly the same time.

So perhaps the interesting question isn't simply, "Do women synchronise each other's periods?"

Perhaps it's whether several rhythmic bodies living within the same environment can sometimes begin responding to some of the same rhythms around them.

And if we're going to ask that question, there's one enormous rhythm outside the window that humans have been watching for thousands of years.

Which brings us right back to the Moon.

Then science started looking

The idea that menstruation could have some relationship with lunar rhythms has moved in and out of scientific interest for decades, partly because the evidence hasn't been particularly straightforward.

A small but fascinating study published in Science Advances in 2021 examined long-term menstrual records from 22 women. Some of those records stretched across many years. The researchers found that menstrual cycles sometimes temporarily synchronised with lunar cycles, particularly at certain ages and under particular environmental conditions. The synchronisation wasn't permanent and it certainly wasn't universal, but there appeared to be something worth investigating. And this was a super small study.

Then, in 2024, a much larger study examined more than 311,000 menstrual cycles from almost 36,000 women in Europe and North America. Again, researchers found a small but statistically significant circalunar rhythm in the timing of menstruation.

It wasn't the enormous synchronisation that popular stories about women and the full Moon might lead us to expect. In fact, the researchers also found a stronger seven-day rhythm, which introduces another fascinating possibility about the interaction between biology, behaviour and the artificial rhythms we create through our working week.

But underneath all of that noise, a small lunar rhythm remained.

That doesn't mean the Moon controls menstruation. It doesn't mean that your cycle should last exactly 29.5 days, and it certainly doesn't mean there's anything wrong with you if your period has never paid the slightest attention to what is happening in the night sky.

It simply gives us another reason to remain curious.

The obvious explanation people often reach for is gravity. The Moon moves the oceans, the human body contains a great deal of water, therefore the Moon must be moving the water inside us too.

It's a lovely idea, but our physiology doesn't really work like a miniature ocean. Water in the human body is contained within cells, tissues, blood vessels and extracellular spaces, and there isn't convincing evidence that lunar gravity produces a meaningful downward pull on the pelvic organs or pelvic floor.

Perhaps, though, we've been looking in the wrong direction.

Perhaps the more interesting connection isn't gravity at all.

Perhaps it's light.

The clocks inside us

We often talk about our "body clock" as though there is one little timekeeper sitting inside the brain. There is indeed a central circadian clock in an area of the brain called the suprachiasmatic nucleus, or SCN, and light entering through the eyes provides one of its most important signals.

But our rhythmic biology doesn't stop there.

There are molecular clocks throughout the body, including within the reproductive system. Researchers have identified functioning circadian clock machinery in the pituitary, ovaries, uterus and oviducts. Individual tissues have their own rhythmic activity while remaining connected with the body's central clock.

In other words, your uterus has some idea what time it is.

Our internal clocks help coordinate sleep and wakefulness, hormone secretion, metabolism, body temperature and countless other biological processes. Light and darkness help keep these systems synchronised with the outside world.

For most of human evolution that outside world behaved fairly predictably. Day was bright and night was dark. Moonlight varied throughout the month and daylight varied throughout the year.

Then we invented artificial light.

Now we can wake before sunrise and immediately flood a room with light, spend most of a bright day indoors, illuminate our houses long after sunset and climb into bed carrying a small glowing screen.

That doesn't mean artificial light is bad or that we need to return to living by candlelight. It does mean that we have dramatically changed one of the environmental signals our biology evolved to interpret.

Research into sleep makes the lunar question particularly intriguing. In 2021, researchers studied sleep across very different environments, including Toba/Qom communities in Argentina with varying access to electricity and university students living in highly urbanised Seattle. They found that sleep changed across the lunar cycle. In the days leading towards the full Moon, people tended to fall asleep later and sleep for less time.

Remarkably, the pattern appeared even in the urban population.

One suggestion is that before artificial lighting, bright moonlit evenings simply allowed humans to remain active for longer after sunset. Moonlight would have genuinely changed what was possible after dark.

Perhaps the important question, then, isn't whether the Moon is somehow reaching down and pulling at our bodies. Perhaps it is how exquisitely responsive our bodies are to the environment around them.

For most of human evolution, those internal clocks were receiving their information from a very different world. Day was bright, night was properly dark and the amount of light we experienced changed with the seasons. Even the night itself changed across the month as the Moon waxed and waned.

And then, extraordinarily recently in terms of human evolution, we changed the rules.

Artificial light allowed us to stretch daytime deep into the night. Industrialisation allowed us to work while our biology was expecting darkness. Today we can wake before sunrise to an alarm, switch on bright lights, spend most of the actual daylight hours indoors, eat late into the evening and finally climb into bed carrying a brightly illuminated screen.

We've changed more than light too. We can keep our houses at similar temperatures in January and July, eat many of the same foods throughout the year and organise our working lives around clocks rather than sunrise, sunset and season. Shift work allows us to reverse day and night completely.

None of this is inherently bad. I'm extremely fond of electric lights and a heated home.

But biologically, it represents an enormous change.

Our bodies evolved within repeating environmental rhythms of light and darkness, activity and rest, warmth and cold, food availability and season. Many of those signals are now quieter, altered or competing with entirely different signals created by modern life.

And we already know that some of this matters. Artificial light at night can alter melatonin and circadian timing. Shift work can disrupt circadian rhythms and sleep, while the timing of food and physical activity can also influence clocks throughout the body.

So perhaps asking whether we've lost our connection with the Moon is actually too small a question.

Perhaps we've changed our relationship with natural rhythm itself.

And this creates a fascinating problem when we try to study it and I have been down some massive to the other side of the world holes researching this blog.

When modern researchers ask whether women's menstrual cycles synchronise with the Moon, they're studying modern women living in a profoundly altered environment. We can't go back ten thousand years, find a group of women living without electric light, illuminated cities, shift work, alarm clocks and screens, and measure their sleep, melatonin, hormones and menstrual cycles for several years.

That experiment is unavailable to us.

Modern studies can tell us what happens in the women and environments being studied today. They can't definitively tell us what the relationship between female biology, natural darkness and lunar light looked like before we changed so many of those environmental signals.

That doesn't mean ancient women definitely menstruated in synchrony with the Moon. We can't simply fill the gap in our knowledge with the story I would most like to be true.

But it also means that weak or inconsistent lunar synchronisation in modern populations cannot, on its own, tell us that a stronger relationship never existed.

Perhaps the faint lunar patterns researchers are finding today are coincidence. Perhaps they're the inevitable consequence of two cycles of roughly similar lengths occasionally falling together. Perhaps they're remnants of something that was once more pronounced under natural light-dark conditions. Or perhaps there is another explanation entirely.

We don't know.

And I rather like that we don't know.

Because perhaps the question isn't simply, "Does the Moon synchronise women's cycles?"

Perhaps the more interesting question is:

What did our rhythms look like when darkness was actually dark?

And then the periods stop

This is where I think the conversation becomes even more interesting because we have almost made menstruation synonymous with female rhythm.

A woman bleeds, therefore she cycles. Then menopause arrives, the bleeding stops and it can feel as though the cycle has ended completely.

But menopause doesn't make us arrhythmic.

The ovarian reproductive cycle changes profoundly, but life doesn’t stop there!! The rest of the body's clocks don't simply stop. Cortisol continues to follow a daily rhythm. Melatonin rises and falls. Body temperature changes throughout the day and night. Sleep and wakefulness remain rhythmic. Metabolism is influenced by circadian timing and the nervous system continually moves through changing states of activation and rest.

The hormonal landscape hasn't disappeared either. It has changed. The large cyclical fluctuations in ovarian oestradiol and progesterone that characterised the reproductive years are no longer occurring in the same way, but the postmenopausal body isn't hormone-free.

Over the last few years we've also become much better at talking about the fact that female physiology can change across the menstrual cycle. Work such as Stacy Sims' ROAR helped bring that conversation into exercise and performance, looking at how changing reproductive hormones might interact with training, recovery, sleep, fuelling and how a woman feels and performs.

Then Sims' later book, Next Level, takes that conversation through perimenopause and beyond. As those reproductive hormonal fluctuations change and eventually menstruation ends, the focus understandably moves away from training around a monthly menstrual cycle and towards supporting the very different physiology of menopause and postmenopause.

But reading those two conversations side by side leaves me with a question.

Do all of our longer rhythms disappear simply because the menstrual rhythm has disappeared?

We know the daily ones don't. Our circadian clocks continue ticking. We continue responding to light and darkness. Cortisol, melatonin, temperature, sleep, metabolism and nervous-system activity continue to rise, fall and change rhythmically.

What seems much less clear is whether there are other, longer repeating rhythms in the postmenopausal female body that we simply haven't identified.

And perhaps part of the problem is that we've lost our most obvious marker.

For decades, menstruation gives us something wonderfully visible to measure against. There it is, approximately every month, allowing us to ask what happened before it, during it and afterwards. When the bleeding stops, that obvious marker disappears. We stop being able to say, "I'm on day 12" or "I'm three days before my period", and perhaps we stop looking for patterns in quite the same way.

Perhaps bleeding was simply the rhythm we could see.

That makes me particularly interested when a woman who is postmenopausal tells me that she still notices patterns in her body. Perhaps there are periods when she sleeps differently, has more energy, notices more pelvic heaviness or tension, finds her bowel or bladder behaving differently, or simply feels stronger and more capable at some times than others.

There may be entirely measurable explanations for those changes. Sleep, stress, movement, nervous-system activity, metabolism and hormonal signalling all interact. There may also be rhythms that we haven't properly identified because, without menstruation providing that obvious monthly marker, we haven't necessarily been looking for them.

And I don't think we need to immediately decide that the Moon is responsible (but maybe..)

But given everything we've just explored about internal clocks, natural light, lunar rhythms and the enormous environmental changes humans have made, I don't think we need to immediately dismiss the possibility of longer rhythms either.

We can simply become curious.

What happens if a postmenopausal woman starts noticing and recording these changes? Do they repeat? Do they gradually drift? Do they relate to sleep, season, stress or activity? Do they bear absolutely no relationship to the Moon whatsoever? Or might there occasionally be a pattern that makes us want to look a little closer?

We don't know.

And that distinction feels particularly important when we're talking about women's health because women's bodies haven't exactly enjoyed centuries of beautifully funded, unbiased scientific investigation. Female pain, sexual function, menopause and pelvic health have all, at various points, been misunderstood, minimised or poorly researched. Women have even historically been excluded from clinical research partly because hormonal fluctuations were considered an inconvenient source of variability.

So I think we have to leave some room between "science hasn't demonstrated this" and "science has demonstrated that this doesn't happen."

They're not the same thing.

Equally, lived experience isn't proof of a particular biological mechanism. A postmenopausal woman saying, "I seem to notice this happening every month," doesn't prove that she has an undiscovered monthly hormonal cycle, and it certainly doesn't prove that the Moon is causing it.

But her observation is still information.

And perhaps, rather than immediately explaining it away, the most useful place to begin is exactly where humans have always begun.

By paying attention and bring awareness to it. To your body.

And this brings me back to the pelvic floor

Your pelvic floor isn't an isolated hammock dangling underneath your pelvis waiting patiently for you to remember your Kegels. It is constantly responding to the rest of you. As you breathe, move, lift, walk, sleep, digest your dinner or rush around feeling stressed, pressure is shifting through your body and your nervous system is continually deciding how much tension, support and protection it thinks you need.

Your diaphragm, abdominal wall, hips and feet are part of that conversation. So are your bowel and bladder, your hormones, your sleep, your experience of pain and the state of your nervous system.

So if a woman tells me there are particular times when her prolapse feels heavier, her pelvis feels more tense, her pain changes or her bladder suddenly seems to have developed a personality of its own, I'm very interested.

That doesn't mean I immediately decide that the full Moon is gravitationally dragging her uterus downwards. We don't have evidence for that.

But neither do I want to dismiss the pattern simply because I can't immediately explain it.

Perhaps she has slept badly for several nights. Perhaps her nervous system has been running slightly hotter. Perhaps hormonal changes are affecting her tissues, fluid balance, sleep or perception of symptoms. Perhaps her bowel has changed, she's moving differently or she's simply exhausted. Or perhaps there are biological rhythms interacting that we haven't completely understood yet.

And that, for me, is much more interesting than trying to prove whether the Moon does or doesn't "affect the pelvic floor".

The pelvic floor is part of a living, adapting, rhythmic human being. Of course its behaviour can change when the rest of that human changes.

Perhaps we've been concentrating so hard on whether humans are still synchronised with the Moon that we've missed an even bigger change.

Maybe we've lost the dark.

Our ancestors lived with bright days and genuinely dark nights. Moonlit evenings actually looked different from moonless ones. Seasons dramatically altered the length of the day. Temperature, food, movement and rest changed with the environment around them.

We have flattened much of that variation. We can make midnight bright and winter warm. We can eat strawberries in December, work through the night and spend a beautiful summer afternoon sitting beneath artificial lights looking at a screen.

I'm not suggesting we throw away the light bulbs and move into a cave. I rather like cosy evenings in a warm room. (although my home is much closer to the stones ages or at least victorian, than most).

But our biology hasn't necessarily changed as quickly as the environment we've built around it.

We are still biological creatures living on a rotating planet. Our bodies still respond to light and darkness, movement and stillness, food and fasting, warmth and cold, stress and safety, activity and sleep.

Perhaps there are other subtler rhythms within that conversation that we haven't completely unravelled.

And I'm comfortable with that.

I love science. I want the research and I want to know how many people were studied, what was actually measured and whether the headline bears any resemblance whatsoever to what the researchers found.

But I don't think curiosity has to stop at the edge of what we can currently measure.

Our ancestors looked upwards and told stories about what they noticed. Scientists now look inwards at hormones, cells, genes and molecular clocks. Those are very different ways of trying to understand a human body, and I don't think one necessarily has to erase the other.

Ancient people didn't always have the explanation right.

Neither do we.

But they watched.

Perhaps that's something worth reclaiming, that awareness.

Not because I want you downloading a lunar fertility app or worrying that you've somehow been menstruating under the wrong Moon for the last twenty years, but because there is something incredibly useful about noticing your own patterns.

Notice how you sleep. Notice when you have more energy and when you want to retreat. Notice your pelvic floor, your bowel, your bladder and the days when movement feels fantastic or your body asks for something different. If you menstruate, notice what happens across your cycle. If you're postmenopausal, keep noticing anyway. Maybe try it with technology like those rings and the watches and then leave them somewhere else and use your own awareness, paper and pen - is there a difference (that would be interesting!).

And perhaps occasionally look upwards too.

Not because I can tell you that the Moon is controlling your uterus from 384,400 kilometres away.

I definitely can't.

But because it reminds us of something that is surprisingly easy to forget.

We aren't separate from nature.

We're living inside it. We occupy a really small percentage of the earth cuddled between the sky, the earth and the seas.

Our bodies are still responding, adapting, changing and keeping time, even when we can't see all of the clocks.

There are rhythms within rhythms within rhythms.

The body is still in conversation.

And perhaps, occasionally, it's worth looking up.

If you'd like to read more

Ecochard R, Leiva R, Bouchard TP et al. (2024). The menstrual cycle is influenced by weekly and lunar rhythms. Fertility and Sterility, 121(4), 651–659. This large study examined more than 311,000 menstrual cycles and found a small but statistically significant circalunar pattern in menstrual onset.

Helfrich-Förster C, Monecke S, Spiousas I et al. (2021). Women temporarily synchronize their menstrual cycles with the luminance and gravimetric cycles of the Moon. Science Advances, 7(5). A much smaller but fascinating long-term study exploring intermittent relationships between individual menstrual and lunar cycles.

Casiraghi L, Spiousas I, Dunster GP et al. (2021). Moonstruck sleep: Synchronization of human sleep with the moon cycle under field conditions. Science Advances, 7(5). Research looking at lunar patterns in sleep across communities with very different levels of access to artificial light.

Sellix MT (2013). Clocks Underneath: The Role of Peripheral Clocks in the Timing of Female Reproductive Physiology. Frontiers in Endocrinology. A useful exploration of circadian clocks within the female reproductive system.

Simonneaux V & Bahougne T (2015). A Multi-Oscillatory Circadian System Times Female Reproduction. Frontiers in Endocrinology. An accessible deeper dive into the relationship between the central circadian system and reproductive physiology.

Wellcome Collection has wonderful surviving examples of medieval medical almanacs and Zodiac Man illustrations showing just how closely medicine, astronomy and astrology once overlapped.

For the mythology, Theoi Greek Mythology provides translated ancient sources relating to Selene, Artemis and Hecate rather than relying solely on modern retellings.

And if you fancy another rabbit hole entirely, trace the etymology of menstruation, menses, month and Moon. Their shared linguistic history is almost as fascinating as the biology.

And if you would like to just have some fun discovering your body, trusting movement and loving being you - get in touch. Contact Abby here.