Body Wisdom and Fertility: 5 Incredible Evolutionary Insights & What Your Body's Trying to Tell You
Updated: Mar 30
Body wisdom is the innate intelligence embedded in our systems, that has evolved across millennia to keep us safe from danger, help us secure food and even to help us find good mates and pass on our genes as efficiently and effectively as possible.
These days, we don’t have to pay much attention to body wisdom and sensations. In the developed world, we can get through the day without having to give it a moment’s real thought.
But our bodies are constantly talking to us. Think about the last time you needed to eat. What happened? Your body sent you a hunger pang. Or when you get nervous? You probably felt it all over your body. OR when you’re faced with a big decision, after you’ve weighed up all the options and exhausted yourself going round and round in circles with logic, what advice do people usually give you..?
"Go with your gut."
Your body is communicating its own smart assessment of the situation to you even when you're not consciously aware of all in the inputs.
There is still a lot of mystery attached to what body wisdom and “going with your gut” means in the sense of reproduction and fertility. Even Charles Darwin, the father of evolution, found it all a bit confusing. He wrote in 1862:
"We do not even in the least know the final cause of sexuality; why new beings should be produced by the union of the two sexual elements. The whole subject is as yet hidden in darkness." - Charles Darwin
And in the present day, scientists will openly admit how what they know is still matched by...what they don’t know.
Despite this, what is crystal clear is that our bodies have historical, evolutionary knowledge that seems to extend beyond our obvious conscious understanding, and occasionally...just occasionally...a scientist will spot something and we’ll get a glimpse of it.
Here are some amazing bits of evolution in practice that scientists have identified around fertility and reproduction that you might want to be aware of….
1. Your Fertility is Highest During the Summer ☀️
A woman's chances of becoming pregnant with IVF treatment are twice as high in the summer.
Particularly when “early” weather conditions (i.e. one month before the treatment cycle) were good.
Variations in natural conception and birth rates have been studied, too. With one notable study by S. Becker first identifying that "seasonal shifts" could explain this.
Well, when you think about it logically, babies born in the spring in pre-modern times before incubators or even central heating would have six to eight months to develop before facing their first chilly, resource-poor winter. i.e. an evolutionary advantage.
It's well known that seasons have an influence on fertility in animals and mammals tend to give birth in spring.
So how does it actually happen?
Well, doctors think that the hormone melatonin (which affects sleep patterns) might act directly on reproductive tissues to make women more fertile during the lighter, summer months.
Dr Simon Wood, whose research into this was discussed at the annual meeting of the American Society for Reproductive Medicine -- says melatonin plays a part in priming fertility, not just in determining sleeping and waking patterns.
The relative abundance of Vitamin D might also play a role.
Nowadays, contraception and planning babies means that this difference isn’t too pronounced across the whole population.
Regardless of this, the medical advice is not to delay until the "seasonally optimal" moment, especially if you’re up against the biological clock, as age still trumps this effect.
2. Who You're Attracted to Might Change Throughout your Menstrual Cycle 😍
Some rather eyebrow-raising research found that women with feminine-faced or unattractive male partners were more likely to lust after other men during ovulation. Whereas women in relationships with more masculine-faced partners did not feel the same spike in attraction to other men.
Is this evolution's way of saying that women should procreate with more manly men?
The results from another study aren't exactly encouraging... It found that women who were mid-cycle (around the time of ovulation) were more interested in short-term hookups with men who came across as cocky and even dishonorable to women. In comparison, at other points in their cycle, they gravitated toward longer-term relationships with kinder, more conscientious, deferential types — "good father material."
But one might ask why a woman's body would push her towards a masculine (shall we say, "bro") who might be more likely to leave her down the line? Wouldn't it make more sense for a woman to be attracted to other traits that imply more long-term relationship benefits such as stability or thoughtfulness rather than just brute force?
It actually wants both.
From an evolutionary standpoint, women really do want it all (duh). We want a mate who will take care of us most of the time (you know: hunt, gather, and provide). However, during more primitive times, to accomplish all that hunting, gathering, protecting, and providing, a man would need to be pretty, well, masculine. And because our species wants to thrive, our brains are wired to seek out sex with a manly man in order to capitalize on his "superior" genes and pass them onto the resulting offspring. This is according to what's considered the "Sexy Son Hypothesis," in which a female's ideal mate is one whose genes will produce male offspring with the best chance of reproductive success...and so, continue our gene legacies.
Most of all this occurs totally outside of our conscious awareness, but might help provide some explanation for what's going on when you feel that spark of "chemistry" with someone. Next time check with yourself, where am I in my cycle?!
3. Body Fat Really is Sexy
Evidence from all over the world suggests that men strongly prefer women who have a lot of body fat (roughly 30% of their body weight). And when we say a lot -- we're talking such high levels of fat- as a percentage that it is literally more than bears settling down to hibernate or whales swimming through icy waters!
But it matters WHERE that body fat is.
Studies show men have a preference for it to be distributed in a particular way: very little in the waist but much more in the hips, buttocks and thighs, producing a small waist-hip ratio.
And that’s why Kim Kardashian is laughing all the way to the bank.
So research can pretty easily tell us WHAT the preferences are, but it’s always been a bit of mystery precisely WHY.
Evolutionarily, men whose preferences steered them to the best mothers would then be more successfully pass on their mating preferences to future generations. But why would fat distributed on the hips, butt and thighs make a woman the best mother, in an evolutionary sense?!
There’s an amazing piece of research that offers a great explanation of why, and it’s all detailed in the book “Why Women Need Fat.” by Dr Steven J. C. Gaulin and Dr William D. Lassek.
A lot of theories say it's because pregnancy and breastfeeding are calorically expensive for women, and fat has a lot of calories. But, that doesn't quite cut it: most mammals have very little fat.
As Dr. Gaulin explains, on a percentage basis, a typical slender young woman has around six times as much fat as the average female mammal:
"So, if moms of every species have to pay the caloric costs of making babies, why would women need so much more fat than monkey or meerkat moms?"
The authors say it’s actually all down to the BRAIN.
You might not know that, aside from water, the brain is mostly composed of fat.
And humans have extraordinarily large brains, around six or seven times larger than expected for a mammal of our size. AND remember...women have six times as much fat as typical mammals. Interesting link, right? So, we need all that extra fat to make bigger brains for our offspring.
But this doesn’t explain why the location of the fat matters….right? Except when the scientists looked a little deeper, they found it does.
The most important kind of fat the brain is made of is an omega-3 called DHA. And guess what: women store DHA in their hips and thighs. It’s there as a store to draw down on while our bodies are assembling the baby’s brain.
Our bodies can’t make omega-3s (that’s why they're an important dietary and supplement focus for people trying to conceive), so it would be deeply, evolutionarily reassuring for a male to see a good store of it literally ON his potential mate, so he could be assured she could build a big-brained baby.
As a side note, the researchers point out that this could even be why there are weight management problems in developed nations where omega-3 consumption is super low: American women have very low levels of DHA in their breast milk, less than half that of the tribal Amazonian women. If American women have a low percentage of DHA in their fat, their bodies may also be driving them to store more pounds of fat in an effort to have enough DHA for their infants' brains. So, make sure you’re getting enough good quality omega-3 if you want to avoid that!
Click here if you want to get this book to read about it all in more detail.
But basically: the body wisdom for women is: we know where to lay down our fat. And for men? They are being directed to find women who have plenty of DHA stores extra appealing!
If this makes it seem like our bodies are just thinking about having a baby and then it ends there...THINK AGAIN. They’re even wiser than that….
4. Your Body is Thinking Long-term
Even if you're not planning life further than the next pay-check, your body has different ideas.
Why we - and females of some other species stop ovulating before the end of our natural lifespan is a longstanding evolutionary puzzle - but it's though to be part of a grander plan.
Reproductive senescence - or the end of our fertile years - occurs much faster than somatic aging. Women have what scientists called "prolonged post-reproductive lifespans" (PPRLs), which is unlike most animals who can continue reproducing far into old age. The reproductive lifespans of elephants, for instance, have increased along with their life expectancies. But that's just not the case for humans.
There is substantial evidence that the reason for this is that grandmothers are super important in human society: as an extra pair of hands and an extra guiding light, they would have provided significant survival and reproductive benefits to their children and grandchildren.
And when you’re not busy still having your own kids, you’re more on-hand to be a useful grandma and help to ensure that your genes don’t survive just one generation...but way beyond that.
Pretty smart, evolution.
5. Your Family Planning Decisions Might Not be as Logical as you Think
It’s easy to think of decisions on things like “how many kids I want” as rational decisions made in the mind and running contrary to body wisdom that would surely be telling us that now resources are plentiful, we should all have loads of kids in order to ensure to maximize the spread of our genes right….?
The "fewer kids paradox" is the apparent evolutionary paradox that the number of children we have declines with increasing wealth, both within and between human populations. So, the wealthier society’s get, the fewer babies people have.
But rather than having fewer kids being our rational minds victory over our innate body wisdom, there are theories that having fewer kids is actually part of evolution and our bodies are in part making these decisions for us, despite us.
It sounds kind of harsh, but our bodies are constantly making the assessment of a trade-off between offspring quantity and quality.
Here’s what we know:
The wealthier you are, the fewer kids you’ll have
Why is this? Despite the abundance of resources people in developed nations can invest in reproduction, we actually have the lowest number of kids per person ever known or suspected for humans.
It might seem counterintuitive that better living standards would be linked to decreased fertility. But it’s all about a NEW survival of the fittest that our collective wisdom interprets. Strategically reducing the number of kids to invest in offspring quality, particularly via formal education, is incentivized as we transition into modern, developed societies.
So one of the ways in which cultural evolution has affected fertility rates is resulting from the trade-off between the number of children and the quality of life that parents desire to give each of them. The resources parents in the global West invest into each child’s upbringing have changed - it’s no longer about food, let's say, it’s about giving your genes an edge from things like education and inheritance, and even the time spent together has become a currency.
The world is still a highly competitive environment, but we’re not competing for food now - and there's not a need to have lots of kids to ensure some of them survive, thanks to better healthcare, nutrition and security. Now, we're competing to give our kids the best status, in order to provide better opportunities for them, which will help snag them a better mate and a better way of passing on all our genes.
When parents have fewer children, this means giving each of them a greater chance of achieving higher status.
This is actually INTENSIFIED if you live in a city. Then, scientists say likelihood is you’ll want to have even fewer kids than someone who lives in a rural area.
The way scientists explain this is: the number of kids you have decreases as you’re surrounded by a higher number of directly competing individuals.
You could just write this off as a rich/poor divide (as people in cities have more access to economic resources) except that doesn't quite hold true in the data. The idea of the number of directly competing individuals being central to the number of children we want to optimally have is supported by birthrate comparisons between many Western European nations and the United States. Birthrates in population-dense European countries (like Germany, Italy, and the UK - where people live closer together in general) are significantly lower than they are in the comparably population-sparse United States, which just has a whole load more open space.
Our bodies and minds are working together, with the lessons learned over the course of millennia, to guide us to the smartest ways to maximize our genes.
And if that's not "wise", we don't know what is....