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International Kissing Day and DNA

Another ‘Awareness Day’, International Kissing Day, is coming up on July 6. It might not seem obvious but kissing, like most subjects can now be easily linked to the science of DNA. Thus, there could be no more perfect opener for my Double Helix column, given the elegance and beauty of a kiss.

To start, there is the obvious biological link between kissing and DNA: propagation of the species. Kissing is not only pleasurable but seems to be a solid way to assess the quality and suitability of a mate. Philematologists, the scientists who study kissing, have accrued scientific evidence that we end relationships based on bad kisses and grow addictions to our partners thanks to good ones that act to douse our brains in dopamine.

We chose to participate in romantic kisses based on our assessment of DNA quality, part of that je ne sais quoi magic of attraction, and kissing creates unique DNA; when the genomes of two parents recombine, the result is a human being with DNA never-before seen on Earth.

The link between kissing and procreation has been known since time immemorial. Now there are some very modern updates to this classic story.

“To kiss” comes from the Old English cyssan, in turn from coss, “a kiss”. While the word kiss is ancient, the word DNA is modern and its use is significantly changing. A linguistic phenomenon is underfoot; DNA is moving beyond the laboratory and into the vernacular. We have adopted the metaphoric application of the term DNA, short for deoxyribonucleic acid, the building block of life, to mean ‘essence of’, ‘basis for’ or ‘soul of’. Social media is filled with “DNA compliments” like “Bless your DNA”. It is not uncommon to hear declarations like “It’s in my DNA to dance”. Porsche vehicle “Design DNA” includes the classic features of this luxury brand such as rear-end engine placement and Porsche’s immediately recognizable, aerodynamic shape.

Using this secondary definition of DNA, we could say, as humans, “it’s in our DNA to kiss”. We could also explain International Kissing Day by saying that its DNA is “to honour the humble kiss as an act of kindness and affection”.

"The Kiss", by 'playingwithbrushes'. CC-BY-NC-2.0 via Flickr.
“The Kiss”, by ‘playingwithbrushes’. CC-BY-2.0 via Flickr.

There are also ‘six degrees of separation’ links as DNA continues to pervade modern culture. The company DNA 11 offers both DNA and Kiss Portraits. You can either see ‘you’ in these non-traditional wall hangings as a series of horizontal bands resembling ladders (your DNA chopped into pieces and run with electricity through a special kind of laboratory jelly) or as lips on canvas. The pop band Little Mix’s hit love song DNA from the 2012 album DNA mentioned the word kiss twice in the lyrics.

Getting into the realm of hard science, “Kiss a Ginger Day” formed in 2009 and each January 12th encourages the public to happily “kiss any and all red-heads”. Red hair is due to genetic mutations in the MC1R gene which is responsible for hair and skin pigmentation. Only lucky people with two ‘red-head’ copies (alleles) can claim this shower of attention.

Companies are emerging that are attempting to put the ultimate modern scientific spin on your chances of getting kissed. They are taking advantage of genetic profiling methods to find ideal partners. “Genetic matchmaking” is a concept pioneered by Claus Wedekind with his “sweaty t-shirt” study published in 1995. He famously showed that women find men more attractive if they have dissimilar immune system genes.

“Kissing DNA”, a phrase yet to be coined, is a recent discovery. Evidence that we are constantly trading DNA is mounting as researchers start to understand the dust cloud of genomes we all leave in our wake. We are constantly shedding cells and all of them contain our DNA. The inside of our mouths are particular rich in easily shed cells and this is why DNA-testing companies across the world rely on cheek swabs and spit samples for source material.

So, what happens when we kiss? Same thing occurs as when a swab is taken – we release our DNA. With a kiss it mingles. The DNA of a lover can be detected in your mouth up to an hour after the act. While for most this is just a pleasant by-product of intimacy, for victims of crime it could be a forensic method of putting assailants behind bars.

It’s not just your own, human DNA you share. You also trade in portions of your ‘second genome’, the community of microbes that colonize us, primarily in our guts.

If you are squeamish about ‘germs’, look away now. Our mouths harbour rich collections of invisible life. It is estimated that a kiss lasting longer than 10 seconds transfers 80 million living bacterial cells.

You get a dose of love-genes when your partner reciprocates the favour. Actually, 80 million is the tiniest fraction of the trillions of microbes in and on your body and diversifying your microbiome could have many beneficial effects.

Setting the world record for the longest kiss would now take a couple willing to exchange DNA for more than 2 days, 10 hours and 35 minutes. Perhaps this record will be exceeded in 2015 in honour of love.

It seems like we are being regaled with a ‘day’ in honour of everything, but kissing, from the platonic peck to the full out lip lock certainly seems an excellent reason to celebrate.

Featured image credit: Kissing, by maumau97. Public domain via Pixabay.

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