Steffen Münzberg | Susanne Thiele | Vladimir Kochergin

Sex is fun – but it means a lot of work, too

Sex macht Spass, aber viel Mühe

Orell Füssli Verlag


The things to come

Excitement phase – What’s it all about?

Sex and death – Why sexuality?

Better go back to virgin birth?
Pros and cons of sexuality

Our first time
When? With whom?
Did you enjoy it?

About DNA and gender affairs
The development of sexes

What separated men and women from each other

Death and old age
What makes us hobble and shrivel

Plateau phase
Sexual choice

It’s election day
Who is allowed to crossbreed with me?

Skin, teeth, hair, face, eyes, hips

Orpheus in the primeval world
What is music, and why?

Sex under construction

Boy or girl?
About the embryos’ hard work to become either male or female

Woman, man – or something totally different?

How the gender enters your brain
Who decides who we are and who we fall in love with?

Phase of relaxation
Humans and other primates

Our hairy relatives
Mating in our evolutionary neighbourhood

Clever savannah walkers
Sex with intelligent side effects

I am faithful to you – and others
Our unusual monogamy within the group

Who is perfect? And if so – how many?
Double and triple strategies

Aaaaaand action!
More pleasure in privacy with primacy




Foreplay – The things to come

This book’s intention is to make you aware of the sexual powers affecting us directly and indirectly – some intentional and some indulgent or undesired but in those cases mostly even more persistent.

Which are the prime movers and shakers of our sexual thinking and behaviour? Where do our preferences, our criteria for choosing a partner – and keeping him or her – originate? How did we become the sexual, loving and social beings we are today? All of these questions and more will be answered in this book.

We will not give you any advice on how to date successfully or how to solve your relationship problems. There are plenty of other books for that. But maybe knowing more about the sexual past of mankind will help you to understand yourself, that special someone and the special others better than before.

In the course of their lives many people realize that in regard to sex, their wishes don’t match reality at all. It’s not easy to deal with that. Self-doubts and blaming the partner are often the consequences. But if you know where this gap between wishful thinking and reality originates, you can manage these tensions a lot better. It is easier to handle wishes and desires if man and woman know why they develop these wishes and desires, and how these feelings as a part of their personality affect others and themselves.

In our book »Sex is Fun« we would like to take you on a journey through the evolutionary history of sex. In the first part, you will learn about how bacteria got us into the whole sex trouble, and how they managed to do this. You will also plunge into the primordial ocean with us and will watch protozoa doing “it”.

Why are there two genders? Why do plant lice propagate virginally but elephants don’t? Why aren’t most of us hermaphrodites – which means: no intersexual hybrids? You will find the answers to these questions in the first part of our book. And since sexuality is closely linked to death, we will have a focus on death and old age in a specific chapter.

While in the book’s first part only bygone single-cell and multi-cellular organisms are active, the second part will have a close look at human peculiarities. There it comes to the old question “who does it with whom?”. You will examine the sexual choice, the choice of a mate – during which in fact nobody has to die, however strict criteria have to be followed. This produces quite interesting blossoms and tails in the course of evolution.

Our preferences in the choice of a partner did not only bring us broad shoulders and wide hips but also romantically glancing eyes and intelligence. Due to their habit of singing, painting or having funny conversations before having sex, our ancestors made music, arts and language grow. In fact, many of the things we call culture have an erotic-evolutionary history and background.

So after all, it was the fascination of screwing that drove humanity to its cultural development! As a matter of fact we slept our way up to become artists and academics, philosophers and scientists.

In the book’s third part we will further examine how embryos come to be female, intersexual or male, and how the gender invades the brain.

At dawn of part four we will sneak into the jungle and spy upon the mating rituals of our hairy relatives.

There is the saying that our most important sex organ should be located between our ears. This sex organ, namely our brain, loves falling in love. But what for? Where do our capacity for love and our desire come from?

Evolution does not only find it quite amusing to see living creatures copulate; no, of all things it additionally teases some species with the desire to fall in love with a sexual partner.

How did love and sex of human beings find each other and were linked together? Or maybe not? Shouldn’t it work without our romantic outbursts of emotion? Our relatives – the bonobos, chimpanzees, gorillas and orangutangs – do not seem to fall in love as a matter of fact. But why do we? In which way did the love for our partner shape us and our society? And how much monogamy can be considered the emotional and evolutionary optimum? In our every day’s and this book’s epilogue, bonobo and company will pay us a visit in the bedroom and add some spice to our sex life.

By the way: In case someone in this text claims to be “me”, it will be Steffen Münzberg. He is responsible and can be blamed for most of the texts. The part “Sex under construction” was written by Susanne Thiele. Unfortunately, Vladimir Kochergin will not be getting a word in. However, he diligently worked on the research and editing part.



Part I

Excitement phase – What’s it all about?


Sex and Death – Why Sexuality?

Why are we having sex? Because it’s fun. Why is sex so enjoyable? So we will have it. If sex wouldn’t be any fun, we wouldn’t mate, wouldn’t breed and would be extinct pretty soon.

But by all means, why do we need sex to multiply? It could work out without sex, right? Bacteria for example reproduce through pure and chaste division. Many plants simply grow an offset, which becomes a new plant later on. Even some animals breed abstinently. A small coelenterate known as hydra or water polyp, and related to the jellyfish family, is able to laterally grow a new hydra out of its own body. It alternately divides across or lengthwise to then become two hydras. Plant lice give birth to young aphids – during summer, aphids won’t lay any eggs but are live-bearing – without the aphid-mum having anything like sex at all. You see, it can work without sex. So why all that mating trouble? Couldn’t we humans simply split in two like a hydra? Waking up in the morning, lying right next to one’s own self? Wouldn’t that be something?


Bacteria food

To understand why us humans have to deal with sexuality, we have to change our perspective. Instead of concentrating on ourselves, we have to focus on viruses and bacteria. No, this is not about bacteria and viruses merrily jumping from human to human during their sexual intercourse; this is much more about the crackling relationship between viruses or bacteria and us multi-cellular organisms. And the question is: Is there a connection between our sex life and the pathogens of influenza or diarrhia?

Just take a look at yourself from a hungry bacterium’s point of view. To a bacterium, a human being is a gigantic accumulation of meat, which could provide nourishment for a long time. And there are many hungry bacteria. Three kilograms of the weight shown on your scales are bacteria living on and in your body. If you are taking a bath in the ocean, in every cubic centimetre of sea water – which isn’t more than a thimble – you’ll find 10 million viruses, desperately looking for a chance to breed inside you. To save us from being eaten by all those many bacteria and viruses, we need a good defence strategy. But which one?

Bacteria break up our cells to eat them. Viruses invade our cells to use them as a hatchery. Breaking up a cell as well as penetrating one are complex biochemical processes: The bacteria and viruses dock on to specific structures on our cell surface and use chemical “keys” to open the cells. We are incredibly lucky that not every bacterium or every virus has the talent to crack open our cells. Otherwise we wouldn’t move around on earth upright and erect but would more likely ooze into the soil. decomposed to cellular liquid by viruses and bacteria.


The key question

On their outer cell membrane surfaces, our cells are equipped with sneaky molecular structures and features. There are sophisticated sugar molecules providing mechanical and chemical protection. There are complex molecules able to understand other cells’ chemical signals and lead them to the inner cell.

And there are molecule pumps, introducing certain substances into the cell and ejecting others out of it. A cell’s surface isn’t a smooth shell but a mixture of molecular mountains, antennae forests and chemical plants.

In order to open a cell, bacteria and viruses need “tools” or “keys” which are biochemically exactly compatible to a certain spot on the cell’s surface. Using such a matching key, viruses and bacteria might trigger certain biochemical reactions within the cell walls, which will open them.

These „Open Sesame“ reactions, which are typically used to smuggle certain beneficial substances into the cell, now open the inner cell to viruses and bacteria. Only the one with the right key to a cell’s surface will get to the food and will multiply. Bacteria see our cells as well-filled storage rooms, refridgerators and wine cellars all in one. And to the viruses, our cells are free maternity wards and nurseries. This may sound harmless, but it isn’t.

The infiltrating virus genes force our cells to assemble huge quantities of junior viruses within themselves. Having grown up in a cell, these juniors want to break free and conquer the world. So they start to destroy the cell from the inside. The new viruses, which are washed out of the ruins of the cell, immediately attack other cells, which will then share the same fate.

But how do viruses and bacteria manage to get the right cell keys? And how can this be prevented?

If one day a new bacterium lands on your body, it is very likely that it won’t immediately have the right key to your cell surfaces. But bacteria have the time on their side. They might divide within 20 minutes, mutating and mutating again and again. Every new mutation brings new chemical keys, so sooner or later there will be the one bacterium that will match your cells. And then you will be nibbled on or even eaten by them.


Happy End

However, there is a safe method to avoid being eaten. It’s a sure-fire method and it’s very easy. Just die! Better die before being eaten and becoming ill as a result.

Hang on! Just a minute! Didn’t we talk about how to survive? How can dying help us to survive? Yes, of course, you are right: This is about survival. But unfortunately it’s not your personal survival we are interested in but that of your genes, the survival of your genetic information. Well, actually the best thing you can do to save your genes from bacteria and viruses is to get children pretty soon, raise them pretty fast and die right away. Then parasites won’t have enough time to decipher your cell wall code. Before bacteria and viruses have the chance to make themselves comfy in your body, you’ve already passed away. And of course you will die fit as a fiddle, since you still don’t have any parasites in your cells. A well-timed death is the most effective survival remedy – if not for you, at least for your genes.

Mayflies demonstrate organized dying. After the mayfly larvae spent many months in the water, they all rise from it at the same time, shed their skin and only live a few days as adult insects capable of flying. However, they are not dying because they can’t live any longer or because they get eaten. No, they die because they have to, due to their genetic programming.

At a specific date, right after mating and egg-laying, they die because it is their duty, for the sake of their species. This is how mayflies cheat predators and parasites. No bird, no dragonfly and not even an ichneumon wasp or mite is able to adapt to the mayflies’ rhythm of flying around only for a few days a year. No species can develop into a specialized “mayfly predator” without starving to death and become extinct.

Even our death is destined. Although we are not dying on a particular day like mayflies, we still die. What makes us die? If it is not for the parasites to carry us off, we die from cancer or old age. Growing older means our cells lose their function. They wear out, because their inner maintenance program degenerates and works less effectively. Also, heavily worn cells will not be replaced any more. However, these seem to be the normal conditions of life, don’t they? Why should aging and the following death be planned in any way? Isn’t aging and dying the inevitable course of all life cycles?

Good news! Aging is avoidable. Aging doesn’t have to be. “Forever young” can be achieved – but only if it is combined with an evolutionary benefit. We will come back to this in chapter seven, when we are taking a closer look at the telomeres, which are supposed to protect us from cancer but also let us die in time. But for now let us get back to the parasites and their favourite dish: us.




Be different!

With beings like humans or elephants, taking a few days longer than the mayflies to generate their offspring in extensive pregnancies and parental care eras, a “quick dying” isn’t easily achieved. Long-living creatures can’t escape the parasites as easily as the “quick dyer”. But apart from an urgent departure, there is another method to escape unscathed by parasites.

Our children are born into a world full of viruses and bacteria. Those parasites living in or on the mother for approximately 20 to 30 years have already found the right cell surface key and immediately pounce on the juniors. If those children – for the sake of simplicity – were born by a virgin, they’d have identical genes to their mother’s, hence identical cell surfaces. Such children are exactly what the parasites would have waited for, since they already had the chance to train on the mother’s cells.

The small ones will be colonized by bacteria and viruses already familiar with the children’s cell surface type. Like a hot knife through butter, the parasites are able to break open their cells. If mother and child are genetically identical, a quick death does not help the genes to survive. The mother might be dead, however her identical blue prints invite to dinner. There is no use in cloning, actually. But what could help? Is there a possibility to give birth to children who will be safe from parasites?

Many multi-cellular organisms use a very elegant method to fool bacteria and viruses. These multi-cellular organisms, a group we are part of as well, give birth to genetically slightly different progeny. Due to the genetic differences, the cell surfaces of children differ from those of their mother. The parasites try to enter but the door stays shut. Their key doesn’t fit anymore. Viruses and bacteria have to start looking for a new compatible cell surface key. As a consequence, the genetically modified offspring has the chance to grow old enough and have children as well before new generations of parasites are ready to open their cells. But how do multi-cellular organisms manage to change their genes on purpose?



Compared to a pre-programmed death, the method used by multi-cellular organisms to carry out the genetic modification of their children is much more inspiring. It is called sex. Gene-mixing is one of the consequences of sexual reproduction.


Sexually produced children carry a different gene-mix than their parents. But how does the gene-mixing work? Is it shaken or stirred?

Gene-mixing starts long before the sexual act itself. When ovum and spermatozoon generate genes, they are already swirling about. The human genotype needs at least 23 different chromosomes to file it. Like in every good governmental office, normal body cells store their files in duplicate. They have a double set of chromosomes with 46 chromosomes altogether. 23 of them were delivered by Mummy, 23 by Daddy.

If for example a liver cell would like to divide asexually without ruffle or excitement, its 46 chromosomes will be copied and reproduced to give a set of them to both of the new liver cells. When it comes to producing ova and sperm in preparation for sex, things proceed a little different.

The 46 chromosomes in charge are not copied, but simply divided in two. One goes left, one goes right. Consequently, completed ova and sperm only have single chromosome sets. But that doesn’t matter. After successful sexual intercourse – the fusion of two cells – everything will be doubled again.

The division of the chromosome into two sets of 23 happens at random. Nobody wants to know whether the very chromosome which is delivered to a new cell originally came from father or mother. That means every gamete – be it ovum or sperm – provides a new, different chromosome mix.

During sexual intercourse, the 23 ragtag chromosomes of one and the 23 motley chromosomes of the other cell willing to fuse join up. The entire set of 46 chromosomes stems from parents and grandparents. However, none of them carries exactly the same combination of the same 46 chromosomes.

But there is even more to it than that when it comes to what our inner gene mixing machine is capable of. When generating sex cells in testicles and ovaries, even chromosome segments are interchanged between the individual chromosomes. Just before the division of cells – when the chromosomes start queuing in an orderly manner in order to be split up into two new sex cells – they get cut up.

Then the chromosome segments are exchanged between parallel chromosomes and build in to the other one. Just imagine two suits with sleeves and pant legs being cut off of one and sewn onto the other. This extra wild mixing of genes is called a “crossing-over” or a “chromosomal recombination”.

By intermixing chromosomes and chromosome segments, every child gets a different mix of genes and therefore a different cell surface than his or her parents. To the parasite, every child is a totally new challenge.

This means, the cards of evolution are reshuffled and redealt for every generation, opening a brand new round of “Life and Death”. Hence the evolutionary objective of a sexual union is the mixing of the genes. And since our chromosomes are pretty sociable, they let us have sex.

Concerning the sexual gene mixing with the purpose of parasite defence, the most important thing is to be different. Different from the others. It’s crucial to incessantly activate new locks which are inaccessible for bacteria and viruses.

Let me clarify this: this is what happens all the time if there is reproduction without sex. If special genes cause effective protection against parasites, they spread out quickly within the population. Pretty soon, there will be many, many creatures with identical genes and cell surfaces.

But as a consequence, in this kind of population, parasites win a lot of room for experimentation. It won’t be long before one of them will find the right key to all of these potential hosts. Healthy multi-cellular organisms will then once again become parasite breeding and feeding sites. Those genes, which have recently been so very triumphant, will die out with their sick and parasite-infested hosts.

Multi-cellular organisms like us, who prefer breeding at a leisurely pace, have no chance to adapt to specific bacteria or viruses through mutation and natural selection. Being real fans of mutation, viruses and bacteria change a lot quicker than we do. The only chance we have to stay fit is to make the parasitizing as uncomfortable as possible for the parasites.

That’s what the sex mixture is for: sex to mix chromosomes and genes. As we stated before, today’s ideal gene combinations will be useless tomorrow, that’s for sure. On the other hand, sometimes those which were useless the day before yesterday might be good again today. Cell surface locks, which previously were vulnerable to parasite attacks, might become useful again some generations later.

Maybe the parasites were focused on other locks in the meantime and lost the ability to open these old, almost extinct ones. Like burglars, who are not able to crack an age-old basement lock because they are not familiar with its construction any more.

The change of locks doesn’t work with inbreeding, by the way. There will be no genetic variances in the gene mixing process, since both parents deliver the same genome. Inbreeding offers no advantages – that’s why most plants prevent auto-pollination and many animals avoid their close relatives as sex partners. So Goethe’s Motto, “Why search every low and high, when good things couldn’t be closer by” definitely can’t be applied when it comes to sex with the aim of gene mixing.

As an additional defence mechanism against parasites, animals have immune systems with antibodies and killer cells. Vertebrates, such as the human being, have highly complex immune systems capable of learning, whereas other animals have more simple immune systems without a learning capacity. Comparable to bacteria and viruses with the intention of cracking the cells of a metazoan, the fighting cells of the immune system try to break open the parasites.

To be successful, an immune system needs the key matching the parasites’ surfaces. Immune systems stock up with many different keys. But only through an incessant renewal of sexually mixing, the immune system’s genome keeps the genetic library of keys big enough to keep up the resistance against new attackers. This means that sex has the function of a vaccination. However, unfortunately not for those having it but for their children rather.  

Alice in Evolonderland

Now we know who is responsible for all that sex and also our certain death – bacteria and viruses. Parasites are keeping us busy. After Alice ended up in Wonderland, she went “Through the Looking-Glass” in the following book. Behind the mirrors, she met the Red Queen on her run-without-progress in the forest. She said: “Now, here, you see, it takes all the running you can do, to keep in the same place. If you want to get somewhere else, you must run at least twice as fast as that!”

It’s the same with those constantly changing parasites. Despite all that running, you can never leave them behind, you can at most be the length of a nose ahead to merely stay alive. Only the one who’s running and changing incessantly is staying alive. And that’s the reason why the theory of explaining sexuality as a reaction to the parasites in constant modification is called the “Red Queen Theory”. It was postulated in 1973 by Leigh Van Valen and describes the evolutionary arms race of different species against one another as an important driving force for evolutionary development. This theory is regarding sex as a weapon in the fight between species. Today, the “Red Queen Theory” is seen as a basic module of evolutionary biology.

Before considering how the sexes originated and how multi-cellular organisms, who have clever sex, can get stronger, healthier and lovelier children, we have to answer another question: “Why do not all of the multi-cellular organisms multiply sexually?” There might be some good reasons to be sexually abstinent.