The Genetics of Love │ How Love Makes Us Human with Dr Anna Machin

Is it down to genes how we fall in love? Sort of.

Some elements of how we behave, and we feel when we are in love are influenced by our genes. Now genes are not deterministic. Just because you carry a particular version doesn't mean that's going to express itself in you, but they increase the chance of it being expressed in you, the phenotype.

The oxytocin receptor gene, which is associated with oxytocin, which is important at the start of a relationship, is highly polymorphic. This means it comes in lots of different versions, which means it underpins a lot of the genetic variation we see in how we behave and feel when we're in love. For example, it influences the likelihood that you will be in a long-term relationship, that you will form a pair bond. People who carry a certain version of the gene are much more likely to be motivated to start a relationship and are much more satisfied by being in one. And if they carry that gene, they're more likely to enjoy membership of a large community.

The oxytocin receptor gene also influences how good you are at theory of mind and empathy.

Now remember, theory of mind is the ability to tell what somebody is going to do next and it's really, really important when you are associating with other people. And empathy is the ability to understand someone's emotional state. Now there are various sections of the oxytocin receptor gene that influence this ability. And the more versions that you carry, the more likely you are to be good at it. It's known as a cumulative effect. The oxytocin receptor gene also influences your attachment style, which is quite surprising to those of us who work with love.

Ten years ago, when I started, I would have said that attachment was entirely psychologically

and environmentally caused, however we now know that it is underpinned by a certain amount of genetic influence. For example, a section of the oxytocin gene influences how likely you are to have an insecure attachment style, to be avoidant or dismissive. But this only will express itself in you if you have had a mental health condition. This is known as differential susceptibility and it shows you the complicated interaction between genes and environment when it comes to love.

The oxytocin receptor gene also influences how sensitive you are as a parent. In combination with a gene known as CD38 which influences the production of oxytocin, some people carry risk variants of this gene, which means they find it harder to bond with their children, to interact sensitively with them. And this is probably because they live at a lower level of oxytocin. When we move to beta-endorphin, variation in the new opioid receptor gene, which is the receptor that links on to beta-endorphin, is known as a gain-of-function gene. And for people who have this gene, it's a small number, they find social rejection much harder to take. It seems to be that when they are dumped by their lover or a friendship breaks up, they seem to experience a bigger opiate withdrawal than the rest of us. So, it's increasingly painful, emotionally and physically.

And finally, if we look at the serotonin transporter gene, serotonin is involved in the obsessive element of love. The lower amounts you have, the more obsessive you will be. However, there is a link between one variant of the serotonin transporter gene and the likelihood you will be single. And it may be that this is because people who have this gene have higher levels of serotonin and therefore, don't really have the obsessive desire to be in a long-term relationship.

In our own study at Oxford, we looked at how the different neurochemicals that underpin love: dopamine, oxytocin and beta-endorphin, were affected by the different sorts of relationships you could have. So, for example, dopamine genes seem to influence the size of your social network, that's how many friends and family you interact with on a daily basis and the involvement in your community. Oxytocin was very important in romantic love, whereas beta-endorphin, remember that's the one that underpins long-term relationships, is associated with romantic love, attachment and empathy.

And we also know that genes can be influenced by your experience as you go through your life. And these can then be inherited by your children. This is the concept of epigenesis, and we now know that epigenesis does affect the oxytocin receptor gene. Now, epigenesis doesn't cause the alteration of the actual genetic code, that's the DNA, but how that is expressed. For example, the process of methylation impacts transcription to RNA and ultimately to the proteins that DNA codes for. Higher methylation is linked to anxious and avoidant attachment styles, the reduced ability for facial recognition, that's being able to recognise those who are close to you, and emotional processing.

In our next video, we will see how the love a child receives as they grow has a direct link with who they become later in life.

Subscribe and hit the bell to get notified once it's out. Bye for now!