“It might be the secret to our recent success as a species” – Michael Londesborough on the science of love


It may not sound as romantic as being struck by Cupid’s arrow, but feelings of love and lust are very much the result of chemical reactions within our body, says Dr. Michael Londesborough, a chemist at the Czech Academy of Sciences. He recently visited our studio to discuss some of humanity’s most powerful emotions from a scientific perspective. I began by asking him if there is any difference in how men and women perceive love.

Michael Londesborough, photo: Luboš Vedral / Czech RadioMichael Londesborough, photo: Luboš Vedral / Czech Radio “First of all I think it is important to reflect on the fact that we all love in different ways and levels. That could also be down to chemical facts in the sense that we are all in a spectrum of different levels of production when it comes to certain chemicals. More importantly, we also have different numbers of receptors to these chemicals at important parts of our body.

"Nevertheless, if I boil it down, then the chief hormones which are creating feelings of love are different for men and women. They are similar, chemically speaking, but different.

“In women it is mainly the hormone called oxytocin. For men it is the vasopressin hormone. Despite their chemical similarities, they are subtly different.

“To what extent this difference leads to the amplified difference in the generated emotional response is a difficult question to answer. However, you are right in the sense that they are slightly different chemically.”

How does the chemistry of love work exactly? You said for example that everyone has different receptors and therefore loves slightly differently. Does this mean that, in a sense, there is someone special for everyone, precisely because of how their brain chemistry would react to each other?

“We know something about the nature of these chemical compounds that can generate love, because specific case studies on animals have been conducted in this respect. The one that I am familiar with is that of the vole, a type of rodent.

“There are two main subspecies of this animal – the prairie vole and the field vole. These are very similar in size, habits and they also eat the same foods.

“The field vole is extremely promiscuous, changes partners very regularly and seems incapable of forming any sort of long term relationship, or taking care of the offspring that are produced by mating.

“Research has shown that if there are many receptors to the love hormones in the amygdala, then this tends to lead to individuals who are more inclined to look for longer lasting, monogamous relationships.”

“The prairie vole seems to behave in the opposite way. It upholds a monogamous relationship with its female partner, they have children and he becomes the sort of family vole.

“Scientists have shown that the difference lies in the number of receptors to the vasopressin hormone in the amygdala, an ancient part of the brain.

“Humans have an amygdala too. It is a sort of almond-shaped cluster located at the centre of our brain, which directs a lot of our fight and flight responses.

“When there is immediate danger for example, there is not a lot of time for one’s frontal lobes to analyse and assess the situation. Rather, you need an immediate response that tells you whether you should run or fight it out. This part of the brain is therefore linked to personality traits such as courage and loyalty.

“Research has shown that if there are many receptors to the love hormones in the amygdala, then this tends to lead to individuals who are more inclined to look for longer lasting, monogamous relationships, something we often associate with loving relationships.

Do we know what creature has developed its brain in this sense the most? Can we for example say that a dog loves more than a cat?

“I am afraid I do not know the answer to that. It is an interesting question however.

“A frequent question is also whether this could be a game changer on dating sites. Something in the sense of: Does male A have more receptors in his amygdala than male B, in which case he is likely to be a more loyal partner in a relationship.

Source: www.memorylossonline.com/glossary/amygdala.html, CC0Source: www.memorylossonline.com/glossary/amygdala.html, CC0 "I don’t know if anyone has ever gone through the trouble of working that out, sounds like a bit of a big data problem. I imagine it must be very complicated to get to that part of the brain and count all the numbers up.”

Would it be possible to produce and sell these hormones that provide us with the feeling of love?

“In chemistry very little is impossible regarding the synthesis of known compounds. Oxytocin and vasopressin are constituted of amino acids, basic chemical units that we find in our food for example.

“These particularly compounds are made out of about nine amino acids, which are chemically linked to one another. There do exist ways of creating these compounds, or isolating them from various natural sources.

“So yes, we could put them in a bottle or a pill if you wanted to. That may not be such a complicated task. What is more difficult however, is the delivery of that particular chemical compound to the right area of your body, whether it is a sexual organ, or in this case more relevantly to the right part of your brain which then generates the right kind of response.

“So it is not a case of simply ingesting the right chemical and then being able to rely on it getting to the right place. Our body is very effective at breaking down large chemicals into smaller ones. That digestive, metabolic process basically makes a lot of things that would otherwise be active, inactive.

“There are some chemicals which can get across this ‘blood-brain’ barrier as it is known. These are often drug type molecules. The fact that we are influenced by molecules such as alcohol is because it can get across this barrier effectively. Getting our two love hormones across this barrier is a more complicated issue.

“However, there are studies about using nasal sprays containing these compounds with the hope that it can cross the ‘blood-brain’ barrier and positively affect the brain. But these studies have been concentrating less on love and more on increasing the feelings of empathy for autistic people.”

So no wonder drug for married couples just yet?

“A frequent question is also whether this could be a game changer on dating sites. Something in the sense of: Does male A have more receptors in his amygdala than male B, in which case he is likely to be a more loyal partner in a relationship.”

“No love potion yet. I assume that if their creation were possible, their existence would already be well known.”

There are of course many so-called love potions out there on the market. I was wondering, has anyone perhaps analysed some of them to find out if they work?

“Throughout history we have a whole plethora of aphrodisiacs. These are not based on the true compounds that generate lovey-dovey feelings such as oxytocin, but they do have some compounds that have an influence on lust.

“After all, love is sometimes used as a euphemism for lust in these potions and lust is something that is far easier to kick into motion biochemically. In this area there are many compounds, mixtures, foods and drinks which can start the process.”

That leads me to my next question. What is the chemical difference between love and lust? How far back do these chemicals go back in evolutionary terms?

“One interesting point, when we look at the chemicals of love and lust, is the relative difference in complexity between these two types of molecules.

“The molecules which engender lust are really simple. That suggests that evolution found them a very long time ago. On the other hand the molecules of love are really complex. That suggests to a chemist, albeit without any specific evidence, that these came later on in our evolution.

“It might in fact be the secret to our recent success as a species. It is only in last tens of thousands of years that we have become really successful and I wonder if that is linked to the evolution of our ability to love. After all it is not necessarily that frequent an emotion in the animal kingdom.

“Therefore it is an incredibly important aspect chemically and socially that evolution found these compounds and we are able to make them in ourselves, generating these bonds of love.

On the subject of lust, men often lose interest in sex immediately after they have it. What is the chemical reason behind this?

Illustrative photo: Free Digital PhotosIllustrative photo: Free Digital Photos “The chemistry of lust begins with hormones such as testosterone for men and oestrogen for women. It should be said that these hormones are multifunctional, not just cantered around lust.

“For example, testosterone essentially focuses you. It gears up your body to become interested in the stimuli presented to you at a particular place in time.

“Once that interest has been put into your physical attributes, for example your eye focus is engaged, your hearing is narrowing in and you are ready for action, you also have a boost of monoamine compounds. Your listeners are likely acquainted with these. They are chemicals such as dopamine, serotonin and noradrenalin.

“These are very simple molecules, far simpler than the hormones that engender feelings of love. These chemicals are released directly in your brain and reinforce you in a sort of ‘Dutch courage’ form of chemical concoction that is persuading you to approach the stimulus that is making you feel interested – the person who sparked that lustful feeling.

“At the same time these chemicals are initiating electrical signals that go down your spinal cord. These begin to stir the production of other chemicals such as nitric oxide in the male or female body, leading to another interesting physical process where you begin producing the chemicals that start up the hydraulics of erectile tissue, whether it is the clitoris or penis.”

"You mentioned the question specifically about men losing interest after sex. Imagine you have this sort of looping system in the brain of monoamine production [dopamine, noradrenaline and serotonin] telling you things like: ‘This is good. Yes, yes, keep going.’ These are really powerful chemicals. It is very difficult to ignore them.

"Because these molecules are chemically so simple, it would seem logical, although I am not sure if this has been proven, that these chemicals are very easy for your body to make. I think that is quite obvious. It is why we often go into cycles of lust relatively easily.

“The molecules which engender lust are really simple. On the other hand the molecules of love are really complex.”

“During sex this cycle works like a feedback mechanism going on and on. At the same time that these chemicals are being produced, they are also breaking down. Your brain has to keep producing them to keep this action going on. This is also looped to ones erectile function.

"However, as soon as there is a release of this chemical tension, the brain thinks it does not need to produce these chemicals any more. Bang! The loop stops and all of a sudden you are left with the naked reality of the situation. If that naked truth is not a properly appropriate one then of course you are left with that hollow feeling of ‘what have I done!’

“Now of course this is the subject of many a Shakespearian sonnet. A particularly good one is sonnet number 129, which perfectly describes this moment of passion and the subsequent feeling when the release is gone and you are left hollowed out.”

You were talking about all these chemicals such as dopamine being released, but before that you said that testosterone keeps you focused. So is the idea that testosterone keeps taking away your attention wrong? For example, can testosterone help you study better if it makes you more focused?


So are people who have more testosterone pretty much better at everything they do?

Illustrative photo: Štěpánka BudkováIllustrative photo: Štěpánka Budková “Not necessarily, due to the fact that you have multiple competing systems going on. Individuals who have a lot of testosterone and can use that nervous energy to really focus on their performance can be excellent athletes, or students doing whatever it might be. However, at the same time, for many, the majority of us perhaps, negative feedback kicks in as well. A sort of overriding sensation of anxiety that comes from that testosterone hit appears.

“If I use the example of siting an exam, there is this anxious feeling. That is linked to the testosterone that is being produced and is trying to get you into gear to put in the right performance. For many of us it has the opposite effect though and we try to find balancing mechanisms to reduce the influence that it has in order to remain calm. Some people can ride that wave, others cannot.”

When people sometimes say the difference between top sportsmen and the rest is their ability to focus, are they referring to our ability to ride that testosterone wave?

“Yes, that is my opinion. It is difficult to link all of these things together, but certainly if you play high-level sport then the ability to use what the hormones such as testosterone are gearing you up to be, then you can convert that into high performance rather than letting that overpower you through anxiety which in turn handicaps your performance.”

“I think this process also transfers to our theme of love. Imagine when you are a young man at a school party or a disco and thinking if you should go for a dance. Testosterone kicks in at that moment and just a fleeting glance in the corner of the roof can get your focus activated. Then the monoamines start entering the chemical process and the question is: Can you use them to gear up your dancing skills and provoke the courage to go and ask for a dance, or do you get the wrong side of this boost and have to leave the room just because you can’t handle the chemical heat that your body is producing?”

Earlier you were talking about how the brain stops producing these lust chemicals. What about when people say they are no longer in love, actual love? Is this also connected to the brain connected to the production of these chemicals?

“Individuals who have a lot of testosterone and can use that nervous energy to really focus on their performance can be excellent athletes, or students doing whatever it might be.”

“That seems very reasonable.”

But we don’t know?

“Something stimulates this production. Especially when it comes to lust I think these are unconscious processes. You do not consciously tell yourself: ‘Ok. I am going to start producing these.’ They do it by themselves.

“Genetically we have evolved to react to certain stimuli. That is why you get a whole spectrum of sexuality by the way. Nothing is evolved with purpose or direction, so every possible stimulus stimulates somebody. Therefore those which stimulate the right response which leads to effective procreation are likely to be the most represented in the whole population.

“Despite these commonalities, we know from this from sexuality in human beings, that almost anything you can think of will stimulate somebody. That means that it can ultimately be something very peculiar that sets of the production of these chemicals which then leads to these sorts of feelings or responses.”

You already mentioned the unwelcome surprises of some of the characters in Shakespeare’s sonnets who wake up. Lust was in fact classified as one of the seven deadly sins by the church in the past and it can lead to the unwanted contraction of diseases. You are a chemist primarily focused on the study the study of borane molecules. I wanted to ask you, is it true that they have the potential to be employed in treating patients who have contracted HIV?

“Yes. Borane hydrides are a fascinating group of chemical compounds which do not occur naturally, we have to make them.

“A lot of the ground-breaking and original work on them was made here in the Czech Republic, specifically where I have my laboratories now in Řež u Prahy at the Institute of Inorganic Chemistry of the Czech Academy of Sciences. One of the things that we are looking at is there use in medicine.

“Our biology evolved in the organic world, but boranes have been around for just over 100 years. Therefore our bodies do not know what to do with them. One of the things that we are looking at is blocking key enzymes in the HIV virus’ life cycle.

“Our biology evolved in the organic world, but boranes have been around for just over 100 years. Therefore our bodies do not know what to do with them. One of the things that we are looking at is blocking key enzymes in the HIV virus’ life cycle.”

“This virus has a life cycle, just like we do. It has needs that need to be satisfied. If I simplify it, once the virus infects a cell it uses the DNA apparatus of the cell to reproduce its own genetic material. This results in a long string of its own genetic material which it needs to cut, just like with scissors in the right place in complete sections which it then pings out to infect other cells.

“These scissors are in fact an enzyme, which can be blocked by certain boranes which we are developing at our Institute of Inorganic Chemistry. These chemicals seem to have a longer lasting effect on these enzymes. That is important, because HIV is very effective in outthinking our chemical attacks.

“It is often the case that medication is effective for a little while, but then the virus gets used to it and finds a way to evolve around it. That is why HIV patients often have to change drugs. The hope is that these borane compounds could be effective for longer.”