Why do humans love kissing? This may be the scientific explanation for the "love brain"...

When we are immersed in the romantic moment of kissing, do you know that the history of human kissing can be traced back thousands of years ago, and a simple kiss actually carries thousands of years of human emotional expression.

NO.1

The historical origins of human kissing

Currently, the earliest record of romantic kissing is generally recognized by the academic community and appeared in religious texts from the Bronze Age in India, around 1500 BC.

As early as 2500 BC, clay tablets in ancient Mesopotamia had recorded two different types of kissing: one was the friendly-parental kiss, which expressed respect and obedience, in which people kissed their elders' feet or the ground; the other was the romantic-sexual kiss, which was erotic and intimate.

A piece of Babylonian clay from 1800 BC

Shows a naked couple kissing

According to a 2024 study by Adriano R. Lameira, an evolutionary psychologist at the University of Warwick in the UK, kissing behavior probably originated about 7 million years ago, when our ancestors were undergoing an important transition from arboreal to terrestrial living.

Life on the ground was not very hygienic, and there were nasty little bugs everywhere, so our ancestors had to help each other clean their hair frequently. Their cleaning method was very interesting - they pursed their little mouths and sucked gently, just like using a mini vacuum cleaner, which was very effective in dealing with little bugs! After each cleaning, they would do a "mouth-to-mouth" action to finish.

As time went by, humans had less and less hair, but this "stamping" action was retained.

No.2

What happens in our bodies when we kiss?

First up is the "love hormone" oxytocin! Not only does it arouse sexual desire and maternal feelings, it also makes us more caring and considerate of others.

Interestingly, people who tried the oxytocin nasal spray were more considerate and warmer in social situations. After using it, the boys said that their wives/girlfriends became more beautiful. This is probably the magic of love!

Our lips and tongues are hot spots for "nerve endings parties"! **The dense nerve endings make this area super sensitive, and the skin is thinner than other parts. **When we kiss, it's like pressing the body's "happy switch": the heartbeat speeds up, the body temperature rises, and a warm feeling of happiness arises spontaneously.

At this time, the "Three Musketeers of Happiness" in the body began to show their power:

1

Dopamine

It reaches its peak in 1-2 minutes, making you feel super happy and stimulating more hormones, making you more addicted.

2

5-HT (Serotonin)

A good helper for learning, memory, and rewards, it is an important contributor to happiness.

3

Endorphins

Together with the first two, it promotes the secretion of oxytocin and can also reduce the stress hormone cortisol, helping you relieve anxiety.

No.3

The romantic dance of brain waves

When two people kiss, their brains dance in sync. Scientists have found that when couples kiss, theta and alpha bands in the brain show amazing synchronization, but this effect does not occur when kissing one's own hand.

It's like two brains dancing a duet, the closer they get, the better their rapport! Moreover, this synchronization not only occurs in a single brain area, but also forms a "super brain network", making the emotional connection between two people closer.

The higher the kissing satisfaction, the stronger the brain synchronization! Some scholars have also found that when kissing, the prefrontal lobe area of ​​the left hemisphere of the brain, which processes positive emotions, becomes particularly active.

NO.4

The most amazing chemistry experiment

Kissing is the most amazing chemical experiment. Through taste, smell, touch, and even invisible pheromones (colorless and odorless chemical signals), we can collect all kinds of little secrets about each other.

Research has found that smell is the number one factor in kissing! That’s because olfactory signals go directly to the emotion and memory centers of the brain.

Through kissing, we can feel:

- How is his/her physical condition?

- Do you pay attention to hygiene?

- Is the smell pleasant?

- Whether there are any health problems

By exchanging saliva containing hormones and other compounds, the brain can also determine whether the other person is actually suitable as a partner. This is why kissing can help you judge the potential health and sexual attractiveness of your date and prevent reproduction between genetically incompatible individuals!

Our armpit sweat, skin oils, and even our breath all contain pheromones, which enter the other person's nose when we are in close contact. These are important clues to help us find the "chosen one"!

NO.5

The magical effect of kissing

Mental Health

Serotonin is a superhero: it fights depression in the brain, promotes gastrointestinal motility in the intestines, and acts as both a constrictor and a dilator in blood vessels. It can help relieve cramps and headaches related to blood pressure, and reduce stress and anxiety. It is also said to help alcoholics reduce their desire to drink.

Beauty and skin care

A deep French kiss mobilizes 34 facial muscles, which can accelerate facial blood circulation, improve muscle tissue relaxation, and consume 5-26 calories per minute. Kissing for 20 minutes is equal to jogging for half an hour!

Protect your health

Each kiss transfers about 80 million bacteria, which can form cross-immunity and enhance immunity. Saliva contains calcium and phosphorus, which is a natural anti-cavity guard and can also wash away dangerous bacteria to make teeth whiter.

In addition, kissing can make people secrete pain-relieving substances similar to morphine. The antibiotics in saliva also have anesthetic effects, which can prevent the formation of stress hormones (corticosteroids) and prevent high blood pressure, high cholesterol, muscle atrophy and insomnia.

Having said so much, have you kissed today? A kiss can not only make you happier and healthier, but also younger! Such a cost-effective thing is worth doing every day!

References

The History of the Kiss: The Birth of Popular Culture by Marcel Danesi, translator: Chen Xiangyang

Alpert,JS(2013).Philematology: The Science of Kissing. A Message for the Marital Month of June.EDITORIAL.126(6),466.

Kort,R.,Caspers,M.,Graaf,A.,Egmond,W.,Keijser,B.&Roeselers,G.(2014). Shaping the oral microbiota through intimate kissing.Microbiome.2,41.

Grammer,K.,Fink,B.&Neave,N.(2005).Human pheromones and sexual attraction.Eur J Obstet Gynecol Reprod Biol.118(2),135-42.

Packheiser,J.,Berretz,G.,Rook,N.,Bahr,C.,Schockenhoff,L.,Güntürkün,O.&Ocklenburg,S.(2021).Investigating real-life emotions in romantic couples: a mobile EEG study.11,1142.

Floyd, K., Boren, JP, Hannawa, AF, Hesse, C., McEwan, B., & Veksler, AE (2009). Kissing in marital and cohabiting relationships: Effects on blood lipids, stress, and relationship satisfaction. Western Journal of Communication, 73(2), 113-133.

de Boer A, van Buel EM, Ter Horst GJ. Love is more than just a kiss: a neurobiological perspective on love and affection. Neuroscience. 2012 Jan 10;201:114-24. doi: 10.1016/j.neuroscience.2011.11.017. Epub 2011 Nov 15. PMID: 22119059.

Berger M, Gray JA, Roth BL, et al. The Expanded Biology of Serotonin[J]. Annual Review of Medicine, 2009, 60(1): 355-366. DOI:10.1146/annurev.med.60.042307.110802

Yano JM, Yu K, Donaldson GP, ​​et al. Indigenous Bacteria from the Gut Microbiota Regulate Host Serotonin Biosynthesis[J]. Cell, 2015, 161(2): 264-276. DOI:10.1016/j.cell.2015.02.047

Cardoso C, Ellenbogen MA, Linnen A M. Acute intranasal oxytocin improves positive self-perceptions of personality[J]. Psychopharmacology, 2012, 220(4): 741-749. DOI: 10.1007/s00213-011-2527-6.

Cardoso C, Ellenbogen MA, Linnen A M. The effect of intranasal oxytocin on perceiving and understanding emotion on the Mayer-Salovey-Caruso Emotional Intelligence Test (MSCEIT)[J]. Emotion, 2014, 14(1): 43. DOI: 10.1037/a0034314.

https://www.science.org/doi/10.1126/science.adf0512 Author: Ning Xuan Science Writer

Editor: Dong Xiaoxian

Reviewer: Zhang Chao, Li Peiyuan